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Medicine & Science in Sports & Exercise:
doi: 10.1249/01.mss.0000433644.52319.aa
Abstract

B-35 Free Communication/Poster - Training, Fatigue, and Ergogenics

Free Access

May 29, 2013, 1:00 PM - 6:00 PM

Room: Hall C

737 Board #213 May 29, 2:00 PM - 3:30 PM

Comparison Of Intramyocellular Lipid Contents Between Antigravity And Non-antigravity Human Skeletal Muscles

Maya Hioki1, Nana Kanehira2, Kiyoshi Shimaoka2, Teruhiko Koike1, Akito Yoshiko1, Akira Saito1, Hisataka Sakakibara1, Hideyuki Takahashi3, Yoshiharu Oshida1, Hiroshi Akima1. 1Nagoya University, Nagoya, Japan. 2Tokaigakuen University, Nagoya, Japan. 3Japan Institute of Sports Sciences, Tokyo, Japan. (Sponsor: Katsumi Asano, FACSM)

(No relationships reported)

The transported free fatty acid (FFA) from the blood is stored in muscle cells as intramyocellular lipid (IMCL) that is known as depot lipid for energy substrate. During aerobic exercise, IMCL in working muscles decreases compared to non-working muscles (Schrauwen-Hinderling et al., 2003), which represents the amount of IMCL dependent on the amount of activation. Therefore, we hypothesized that the resting IMCL level in antigravity muscles is lower than that in non-antigravity muscles, because antigravity muscles are more active than non-antigravity muscles during our daily life.

PURPOSE: The purposes of this study are to compare IMCL contents between antigravity (quadriceps femoris) and non-antigravity (hamstrings) muscles, and to determine the relationship between IMCL contents for each muscle and FFA levels.

METHODS: Fourteen physically active men (n = 8) and women (n = 6) (mean age 21yr, body mass index 22.1 kg/m2) participated in this study. 1H-magnetic resonance spectroscopy (MRS) spectra of the vastus lateralis (VL) and biceps femoris-long head (BFl) muscles at the mid-thigh were acquired using a 3.0 tesla whole-body MR system. Axial T1-weighted localizing images were initially acquired to determine the place for a region of interest (ROI). 1H-MRS spectra with and without water suppression were taken using PRESS sequence with the following acquisition parameters: repetition time/echo time, 4000/30msec, 128 averages. Calculation of IMCL contents was performed by LCModel software (v.6.2-2B). Fasting blood samples were collected for measurement of FFA.

RESULTS: IMCL contents of VL (8.8±6.2mmol/kg wet weight) and BFl (7.6±4.1mmol/kg wet weight) were similar. There was a significant correlation between IMCL content and serum FFA levels for both muscles (VL, r=0.61; BFl, r=0.62; all p<0.05).

CONCLUSIONS: These results suggest that IMCL contents in antigravity and/or non-antigravity muscles may change, if any, by our daily activities; however, this might not be detectable using 1H-MRS. This hypothesis may also be supported IMCL and FFA relationship that IMCL depot might occur quickly from FFA when IMCL was used as an energy substance during daily life. This study was supported by KAKENHI grant #23650432 and the Descente and Ishimoto Memorial Foundation for the Promotion of Sports Science.

738 Board #214 May 29, 2:00 PM - 3:30 PM

The Metabolic and Cardio-Respiratory Effects of Abdominal Electrical Muscle Stimulation During Steady-State Exercise

Amanda J. Salacinski1, Steven Mauk1, Dimitria Vandarakis2, Craig E. Broeder, FACSM2. 1Northern Illinois University, DeKalb, IL. 2Exercising Nutritionally, LLC, Naperville, IL.

(No relationships reported)

We have previously showed that electrical muscle stimulation (EMS) significantly increases resting energy expenditure (EE) and enhances whole body fat oxidation.

PURPOSE: This follow-up study was to determine if EMS could also potentiate EE during steady-state sub-maximal exercise in healthy, active adults.

METHODS: Thirty-eight subjects (males =19; females =19) participated. Each subject performed a Block short-form food frequency questionnaire, body composition assessment (Inbody 520), a free-living physical activity assessment (BodyMedia Armband), a maximal aerobic capacity treadmill test (VO2max), and an EMS accommodation-training period. Each subject performed in duplicate two 20-min treadmill trials at 3.0 mph 5% grade with (Treatment) and without EMS (Shame condition). The EMS intervention used a contraction phase = 6-sec at 85Hz; rest phase = 4-sec at 10hz at the highest intensity a subject could tolerate based on the accommodation training.

RESULTS: Subject characteristics were age (27.9 ± 6.9 yrs), Wt (168.1 ± 37.4 lbs), body fat (21.2 ± 8.7%), VO2 max (44.0 ± 8.3 ml/kg/min), 24-hr EE (2,881 ± 637 kcal), average daily steps (10,630 ± 4,687). Test-retest data showed that both the non-EMS (Delta: 1.2%; r-value: 0.93; SEE: 15 kcal; p-value 0.0001) and EMS trials (Delta: 0.8%; r-value: 0.94; SEE: 27 kcal; p-value 0.0001) were highly reliable. During exercise with EMS, Ve = +9.6%, EE = +4.4%, VO2 = +4.6.%, and HR = +8.3% increased (p-value = 0.0001). Male and females responded similarly and the effect of EMS activation on EE and VO2 were independent of a person’s EMS activation tolerance level (low tolerance = +18.3 ± 2.0%; high tolerance = +20.3 ± 2.5%, NS). Fat-free weight (r-square = 0.78, p-value = 0.0001) and trunk lean tissue (r-square = 0.79, p-value = 0.0001) were the strongest correlates with EE during exercise.

CONCLUSIONS: Results indicate the Contour MX9 EMS system increases a person’s EE with acute steady-state exercise. Future studies need to determine if adding EMS activation at rest or during sub-maximal exercise can enhance insulin sensitivity, improve glucose tolerance, and cardio-respiratory adaptations in individuals with low exercise capacity.

739 Board #215 May 29, 2:00 PM - 3:30 PM

The Effect of Plyometric Training on Running Economy and Titin

Joseph Pellegrino, Charles L. Dumke, FACSM. University of Montana, Missoula, MT.

(No relationships reported)

Running Economy (RE) relates strongly to performance but remains poorly understood. It has been postulated that a spring like action may provide free energy to explain improved RE. While several activities such as plyometrics have been shown to improve RE, its physiological basis remains elusive.

PURPOSE: To examine the effect of plyometric training on RE and total titin (TTN) and T1 and T2 titin isoforms.

METHODS: 25 experienced recreational runners were recruited to participate in, and 20 fully completed, a running economy study employing a 6-week, 12-session plyometric training routine. Participants were matched by age, sex and various fitness parameters and randomly assigned to the plyometric treatment (P, N=9) or control group (C, N=11). Pre and post intervention outcomes included body composition, vertical jump (VJ), sit-and-reach (SR), VO2max, OBLA, a 3K TT, RE, and a vastus lateralis (VL) muscle biopsy for protein analysis.

RESULTS: P and C did not differ in any of the outcomes prior to the plyometric intervention. Plyometric intervention resulted in improved running performance (3K TT: C 1.7%, p > 0.05 P = 2.5% faster, p = 0.02) but did not improve RE. C demonstrated improved flexibility and a decrease in VJ, while there were no changes in P (C: SR = 3.9 cm increase p = 0.01; VJ = 3.3 cm decrease, p < 0.05; P: SR = 0.2 cm decrease, p > 0.05; VJ = 0.23 decrease, p > 0.05). While there were trends for a decrease in the T2 titin isoform in P but not C (P1 = 0.22, P2 = 0.16; C1 = 0.22, C2 = 0.22; p = 0.08), no significant differences were found in TTN, or either of the two isoforms following plyometric training. Correlational analysis revealed a negative relationship for RE at all speeds with flexibility (r = -0.46, p = 0.04) and between RE and TTN, T1, T2 and the T1:T2 ratio at several running speeds (r < -0.4, p < 0.04). TTN, T1 and T2 correlated positively with VJ (r > 0.4, p < 0.05).

CONCLUSION: Plyometric training improved running performance despite no measurable change in RE. Correlational data showed greater TTN associating with greater oxygen consumption, which suggests that TTN in the VL does not act as a spring-like source of free energy during running. A more running specific biopsy site (gastrocnemius) and a longer training intervention are suggested for future studies.

740 Board #216 May 29, 2:00 PM - 3:30 PM

Effects Of Exercise Training And Coenzyme Q10 On Acute Exercise-induced Oxidative Stress In Muscles

Nilsel Okudan1, Serdar Balci2, Muaz Belviranlı1, Serkan Revan2, Hakkı Gokbel1, Hamdi Pepe2. 1Faculty of Medicine Selcuk University, Konya, Turkey. 2School of Physical Education and Sports Selçuk University, Konya, Turkey.

(No relationships reported)

Although acute exhaustive exercises increase oxidative stress, it has been shown that aerobic exercise training upregulates antioxidant defense systems. However, little is known about the combined effects of CoQ10 and aerobic exercise training on acute exhaustive exercise-induced oxidative stress.

PURPOSE: To determine the effects of aerobic exercise training and CoQ10 supplementation on acute exhaustive exercise-induced oxidative stress in gastrocnemius and soleus muscles of rats.

METHODS: Sixty four adult male Wistar rats were used in the study and they were divided mainly into two groups: trained and control. Each group was further divided into four subgroups: rest, exhausted, rest with CoQ10, exhausted with CoQ10. The aerobic exercise training program consisted of swimming exercise for one hour per day, five days per week, for six weeks. The CoQ10 was administered by intraperitoneal injection at a daily dose of 10 mg·kg-1 of body weight for six weeks. At the end of the exercise training, rats in the exhausted exercise groups were forced to swim until exhaustion and then they were immediately sacrificed, while rats in rest group were sacrificed at rest. Gastrocnemius and soleus muscles were removed for the analysis of the oxidative stress and antioxidant defense markers.

RESULTS: Glutathione levels were not affected by exhaustive exercise, training and CoQ10 supplementation in gastrocnemius and soleus muscles (P>0.05). Superoxide dismutase activity increased in the gastrocnemius muscle and decreased in soleus muscle with exercise training (P<0.05). Exercise training induced a decrease in 8-hydroxy-2’-deoxyguanosine levels in both tissues (P<0.05). In gastrocnemius muscle, malondialdehyde levels were not affected by exercise training. It was significantly reduced with exercise training in soleus muscle (P<0.05). Exercise training reduced to increase protein carbonyl levels in gastrocnemius muscle induced by exhaustive exercise (P<0.05).

CONCLUSIONS: CoQ10 supplementation alone or in combination with exercise training does not affect the exercise-induced oxidative stress. Training alone may be adequate for the positive effects on oxidative stress in both muscle tissues.

741 Board #217 May 29, 2:00 PM - 3:30 PM

Characterization Of Skeletal Muscle Fiber Type Changes Induced By Aerobic Exercise In Rat Soleus Muscle

Denis M. Silva, Sandra P. Pereira, Luan Tonelli, Alexandra André, Carlos A. Fontes Ribeiro, Paula C.B, Tavares. University of Coimbra, Coimbra, Portugal. (Sponsor: Sponsor: Romain Meeusen FACSM, FACSM)

(No relationships reported)

It has been demonstrated that aerobic exercise may change skeletal muscle fiber type. However, the mechanisms underlying this change are still controversial.

PURPOSE: This work aimed to study possible mechanisms associated with the exercise induced changes in skeletal muscle fiber type. Thus, the relationship between nitric oxide synthases (NOS), VEGF and muscle fiber type change was studied, since NO regulates VEGF expression and VEGF has been shown to regulate NOS.

METHODS: An exercise animal model was used. All the animals’ experiments and treatments were in agreement with the national and international guidelines regarding the experimental use of animals. Eighteen male Wistar rats (∼250 g) were performed an aerobic training for 8 weeks in a treadmill. At the end of the training period the training efficiency was assessed, and blood collected from the jugular vein, after which all the animals were sacrificed by anesthetic overdose. The soleus muscle was removed and stored for further analyses. To evaluate the soleus muscle fiber type the enzymatic method of ATPase detection, was performed. The expression of the NOS isoforms was assessed by western-blotting using the antibodies against iNOS and cNOS (Santa Cruz). The serum VEGF concentration was quantified by an ELISA commercial kit (R&D systems).

RESULTS: The aerobic training increased the number of type I muscle fibers and reduced the type II number. These changes were associated with an increase in iNOS and, principally, cNOS expression. Concerning VEGF serum concentrations, a significant increase in the trained group was verified, which was also positively correlated with an increase in the capillary/fiber ratio.

CONCLUSIONS: Our results showed an increase in the type I fiber type induced by aerobic exercise. They also suggest that iNOS and, principally, cNOS and VEGF are implicated in fiber type change induced by aerobic exercise.

742 Board #218 May 29, 2:00 PM - 3:30 PM

Elevated Stearoyl-CoA Desaturase-1 Expression in Skeletal Muscle Enhances Exercise Capacity

Michael P. Rogowski, Arwa Aljawadi, Chad M. Paton. Texas Tech University, Lubbock, TX.

(No relationships reported)

PURPOSE: Stearoyl - CoA desaturase-1 (SCD1) catalyzes the conversation of saturated fatty acids into monounsaturated fatty acids, a perquisite process in triglyceride formation. Studies have shown elevated SCD1 expression in skeletal muscle in response to endurance training, although it is unclear what role it has in training adaptations. In order to examine the independent effect of increased skeletal muscle expression of SCD1 on exercise capacity, we created a transgenic mouse model with constituent over expression of SCD1 (actin SCD1 Tg).

METHODS: Wild type (WT) C57Bl/6 and actin SCD1 Tg mice were used for the study. Expression profiles indicated that SCD1 overexpression was restricted to skeletal and cardiac muscle only. To assess exercise endurance, sedentary mice were familiarized on an automated treadmill for 4 days, after which they underwent an exhaustive bout of exercise to measure time to fatigue at 18 meters/min at 0°. Fatigue was defined as remaining on the shock pad for 10 seconds. Skeletal muscle was collected from mice to assess β-oxidation proteins and mitochondrial content in WT and actin SCD1 Tg. Peroxisome proliferator-activated receptor Δ (PPARΔ) and peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1) protein concentration was assessed by western blot and mitochondria content was determined. In vitro testing was conducted on mouse C2C12 muscle cells treated with either 100μM oleate (the primary product of SCD1 activity) or linoleate during cell differentiation to measure select fatty acid effects on PPARΔ expression.

RESULTS: Actin SCD1 Tg had significantly longer exercise duration compared to WT (71.9 ± 9.5 min vs. 6.6 ± 3.4 min p<0.001). Transgenic mice displayed increased mitochondria DNA in skeletal muscle as well as elevated PPARΔ and PGC-1 content in red gastroc. Treatment of C2C12 cells with 100μM oleate or linoleate increased PPARΔ expression (p<.05) in maturing C2C12 myocytes.

CONCLUSIONS: Elevated expression of SCD1 in skeletal muscle appears to be sufficient to enhance exercise capacity in mice. By increasing oleate formation, SCD1 may act to conserve linoleate, thereby providing ligand to activate PPARΔ. This likely mediates an enhanced metabolic profile via increased PPARΔ activity and mitochondrial biogenesis via PCG-1 as a result of SCD1 overexpression.

743 Board #219 May 29, 2:00 PM - 3:30 PM

Effects Of Exercise Training Of Different Intensities On Capillary Network In Skeletal Muscle With Non-obese Type 2 Diabetes

Hidemi Fujino1, Hiroyo Kondo2, Shinichiro Murakami3, Masayuki Tanaka1, Fumiko Nagatomo4, Naoto Fujita1, Akihiko Ishihara4. 1Kobe University Graduate School of Health Sciences, Kobe, Japan. 2Nagoya women’s University, Nagoya, Japan. 3Himeji Dokkyo University, Himeji, Japan. 4Kyoto University, Kyoto, Japan.

(No relationships reported)

Physical activity has been shown to be an effective treatment in the prevention of diabetes-induced microvascular complications.

PURPOSE: This study determined the effects of different intensity exercise training on the capillary network and the associated angiogenic factors in skeletal muscles of non-obese type 2 diabetic rats.

METHODS: Wistar (control) and three groups of non-obese diabetic Goto-Kakizaki (GK) rats were studied: control (Con), GK (T2DB), GK with low-intensity exercise training (T2DB+LIT, blood lactate concentration 4 mmol/L) groups. The rats in the exercise training groups were familiarized with running on a motor-driven treadmill for one week and then ran 5 sessions per week for 3 weeks. The 3-D capillary network of the soleus muscle was visualized using confocal laser microscopy. Microscopic images were scanned for 50 μm in depth at 1 μm per slice thickness and displayed as 3-dimensional images. The expression levels of AMPK, GLUT-4 and angiogenic factors (VEGF, Flt-1, KDR, Angiopoietin-1, Angiopoietin-2, Tie-2, and HIF-1 alpha) in the soleus muscle were determined by TaqMan probe-based real-time PCR.

RESULTS: The capillary volume of soleus muscle was higher in the T2DB+LIT and T2DB+HIT than in the Con and T2DB, whereas that in the T2DM was the lowest. In addition, there is no difference between the T2DB+LIT and T2DB+HIT in the capillary volume of soleus muscle. The AMPK and GLUT-4 levels were higher in the T2DB+LIT and T2DB+HIT than in the T2DB. The Flt-1, ANG-1 and Tie-2 levels were lower in the T2DB than in the Con, whereas the levels of all angiogenic factors, except KDR, were higher in the T2DB+LIT and T2DB+HIT than the Con and T2DB. In addition, there is no difference between the T2DB+LIT and T2DB+HIT in the almost angiogenic factors of soleus muscle.

CONCLUSIONS:These results revealed that exercise training is effective to maintain the architecture of capillary network in diabetic skeletal muscle.

Supported by Grants-in-Aid for Scientific Research from the Japanese Ministry of Education, Culture, Sports, Science and Technology.

744 Board #220 May 29, 2:00 PM - 3:30 PM

Epigenetic Networks and Skeletal Muscle Plasticity to Resistance and Endurance Exercise in Type-II Diabetic Obesity

David S. Rowlands1, Mamta Giri2, Rachel Page1, William Sukala1, Birinder Cheema1, Irum Hyatt1, Isobelle Lys1, Funda Suer2, Joseph Devaney2, Benjamin Leiken2, Gina Many2, Eric P. Hoffman, FACSM2. 1Massey University, Wellington, New Zealand. 2Center for Genetic Medicine Research, Washington, DC.

(No relationships reported)

Epigenomic modification of the transcriptome by DNA methylation and post-transcriptional gene silencing by microRNAs are potential environmental modulators skeletal muscle plasticity to exercise rehabilitation in people with obesity and type-2 diabetes.

PURPOSE: Identify novel methylation and microRNA associations with leading processes directing adaptation to chronic exercise in type-2 diabetic skeletal muscle.

METHODS: Biopsies of the Vastus Lateralis were collected from middle-aged (49 y ± 5) Polynesians with metabolic syndrome and morbid obesity (44 kg/m2 ± 10) before and following 16-wk supervised progressive resistance (n=9) or endurance training (n=8). The transcriptome, methylome (Infinium 450k), and global microRNA expression were determined from microarray. Ingenuity Pathway Analysis was used to construct networks connecting methylation and microRNA into disease and functional modules. Network outcomes were evaluated against select protein phenotype outcomes.

RESULTS: Reductions in intramyocellular lipid and increased mitochondrial β-hydroyxlacyl-CoA-dehydrogenase and cytochrome-C-oxidase activity were associated with lipid metabolic and antifibrosis networks with both forms of training; however, only with endurance were functional networks and protein phenotype (increased hexokinase, GLUT4, capillary density) associated with decreased glucose metabolic disorder and vasculogenesis. MicroRNAs connected with glucose metabolism disorder, vasculogenesis, and antifibrosis modules altered in response to endurance exercise included miR29b-3p, miR30c-5p, miR-301a-3p, miR-302d-3p; while fatty-acid metabolism and insulin resistance networks connected miR-222-3p, miR-137, miR-1305, miR-181a-5p, and let-7a-5p. Hypomethylated hub genes included NOTCH4, EPAS1, DLC1, CNTFR, and ACTN4. In response to resistance exercise: antifibrosis overlapped with leukocyte migration and muscle development, with miR-26a-5p, miR-16-5p, and miR-208b-3p, miR-544-3p, miR-377-3p, and hypomethylated genes PAX7, COL4A1, PRKCB, PDGFB, LAMA4, APOE, connected as candidate epigenetic regulators.

CONCLUSIONS: An integrated network approach yields new potential epigenomic regulators of skeletal muscle plasticity to chronic exercise training in obese type-2 diabetes.

745 Board #221 May 29, 2:00 PM - 3:30 PM

Case Report: Mitochondrial Responses To Endurance Electrical Stimulation Training In Persons With Spinal Cord Injury

Melissa L. Erickson, Terence E. Ryan, Hui-Ju Young, Kevin K. McCully, FACSM. University of Georgia, Athens, GA.

(No relationships reported)

Spinal cord injury (SCI) results in changes to skeletal muscle, including a reduction in mitochondrial capacity. Electrical stimulation (ES) therapy is currently used to cause hypertrophy of paralyzed muscle, although the effects of ES on mitochondrial function are unknown. PURPOSE: Use near infrared spectroscopy (NIRS) to measure changes in mitochondrial capacity to a twitch ES endurance training protocol. METHODS: One male participant with SCI (C5-C6, AIS A) completed 12 weeks of ES on the quadriceps muscles. Frequency of ES, duration of training sessions, and number of training sessions per week, progressively increased based on visual observation of muscle fatigue. The initial training session consisted of 2 Hz for 10 minutes and by week 12 reached 7 Hz for 75 minutes. NIRS was used to measure the rate of recovery of muscle oxygen consumption after electrical stimulation (mV02) as an assessment of mitochondrial capacity pre and post training. RESULTS: Pre-training NIRS measured rate of recovery of mVO2 was 0.52 min-1. Post-training measurements of rate of recovery of mVO2 were performed three times within 1 week and were 1.43, 1.46, and 1.40 min-1. CONCLUSION: After 12 weeks of electrical stimulation training, mitochondrial capacity increased 3-fold, to near the values for able bodied individuals. There was also qualitative evidence of increased fatigue resistance and faster wound healing rates during ES training. Future research will be needed to determine the effects of endurance training on mitochondrial capacity and leg health in the SCI population. Supported by NIH Grant R01 HD039676.

746 Board #222 May 29, 2:00 PM - 3:30 PM

Rehabilitative Exercise Improves Skeletal Muscle Oxidative Capacity In Severely Burned Children

Craig Porter, Elisabet Børsheim, David N. Herndon, Oscar E. Suman, FACSM. University of Texas Medical Branch, Galveston, TX.

(No relationships reported)

Skeletal muscle wasting and derangements in skeletal muscle bioenergetics are hallmarks of the pathophysiological response to burn injury. When coupled with prolonged immobilization, this leads to impaired functional capacity in burned patients. Subsequently, strategies that improve skeletal muscle function in this patient population will likely hasten rehabilitation.

PURPOSE: We assessed the effects of rehabilitative exercise on indices of skeletal muscle oxidative capacity in severely burned children.

METHODS: Skeletal muscle biopsies were obtained from burned children (≥40% total body surface area burned; TBSA) at discharge from hospital (control, n=8), and patients who remained at our hospital following discharge to participate in a 12 week exercise program (exercise, n=11). Citrate synthase (CS) and β-hydroxy acyl-CoA dehydrogenase (β-HAD) activities were determined spectrophotometrically in muscle homogenates as markers of mitochondrial content and oxidative capacity, respectively.

RESULTS: Patients in both the control and exercise group had similarly large burns (means±SD; 53±14% vs. 52±9% TBSA). Skeletal muscle CS activity was greater in the exercise group when compared to control (22.6±4.4 vs. 10.3±1.3 μmol.min-1g-1 respectively, P<0.05). Similarly, skeletal muscle β-HAD activity was significantly higher in the exercise group when compared to control (4.17±1.07 vs. 1.61±0.32 μmol.min-1g-1 respectively, P<0.05). However, β-HAD activity normalized to CS activity was not different between groups.

CONCLUSIONS: Skeletal muscle oxidative capacity is greater in burned children who have participated in a rehabilitative exercise regime, largely due to greater mitochondrial content. These data underscore the vital role exercise plays in restoring skeletal muscle function in severely burned patients. Supported by NIDRR (H133A070026, H133A70019, H133P110012), NIH (P50-GM60338, R01-HD049471), and Shriners Hospitals for Children (84080, 840902 and 71009) grants.

747 Board #223 May 29, 2:00 PM - 3:30 PM

Effect of Spinning on Body Composition, Physical Fitness and Vascular Compliance in Obese Middle-aged Women

Young-A Park1, Dong-Hee Kim1, Ha-Yan Lee1, Doo-Hong Kuk1, Woo-Suk Jung1, Seok-Hwan Kim1, Hyun-Woong Moon1, Go-Eun Hong1, Michael G. Bemben, FACSM2, Daeyeol Kim2, Sung-Chae Cho3, Mee-Hyun Yang4, Jong-Wook Park5. 1Chonnam National University, Gwangju, Republic of Korea. 2University of Oklahoma, Norman, OK. 3Mokpo National Maritime University, Mokpo, Republic of Korea. 4Gwangju Women’s University, Gwangju, Republic of Korea. 5Sehan University, Yeongam, Republic of Korea.

(No relationships reported)

Regular endurance exercises generally improve body composition and muscular endurance and can decrease the risk of cardiovascular diseases in obese populations, however, it is unknown if spin training can produce similar effects.

PURPOSE: To investigate the effects of 8 weeks of spinning training on body composition, vascular compliance, and health-related fitness in middle-aged obese women.

METHODS: Subjects were randomly assigned to either a spinning group (n=6) or control group (n=6, no exercise). The spinning group trained for 50 minutes per session, 3 times per week. The training intensity for weeks 1 to 4 was set at 50-60% of maximal heart rate (HRmax) and then increased to 60-70% HRmax for weeks 5 to 8. Body composition (weight, % body fat, and Lean body mass (LBM) assessed by bioelectrical impedance analysis (BIA)), health-related fitness (cardiopulmonary endurance, hand-grip strength, sit-ups, and flexibility by Helma program) and vascular compliance (arterial arteries of lower limb and upper limb compliances by PP-2000 system) were determined before and after the spinning training period. Group comparison between training and control groups were analyzed by an independent t-test following the 8 week training program and statistical significance was set at α=0.05.

RESULTS: Improvements following spin training included significantly lower (p<0.05) body weight and % body fat, but LBM did not change. Additionally, arterial compliance, cardiopulmonary endurance, hand-grip strength, and sit-up performance significantly increased (p<0.05) for the spinning group. There were no changes in any parameter for the control group.

CONCLUSIONS: These results suggest that 8 weeks of spinning training has positive effects on the body composition, health-related fitness, and vascular compliance in middle-aged obese women.

748 Board #224 May 29, 2:00 PM - 3:30 PM

Effects of Repeated Maximum Endurance Strength Exercise on Muscle Damage and Repair in Collegiate Female

Eisuke Hiruma1, Masakazu Umimura2, Shizuo Katamoto3. 1Teikyo University, Tokyo, Japan. 2Umimura hospital, chiba, Japan. 3Juntendo University, Chiba, Japan.

(No relationships reported)

PURPOSE: To determine relationship among muscle damage, recovery and adaptation following repeated bouts of daily muscle endurance exercise in 3 or 7 consecutive days.

METHODS: The 40 female subjects (age:21.1±1.8 yr), had performed in some moderate exercise regularly, were assigned to one (one-group:n=9), three repeated exercise (3-group:n=9) or seven repeated exercise groups (7-group:n=12). This study examined creatine kinase activity (CK), dorsiflexed ankle joint angle (ROM), scale of perceived pain during resting (SPrest), maximum circumference of calf muscle (CCM), isometric muscle strength on lower leg (IMS) and long jumping of one leg (OLJ) in before and after daily exercise for 3 or 7 days of exercise periods. In the exercise period, the subjects performed the maximum calf raise exercise at 1 movement per 2 seconds as long as possible. Subjects counted daily walking steps by walking step counter during this study. The primary analysis consisted of a three-way ANOVA test.

RESULTS: All subjects walked 7000 to 8000 steps per day. CK after the initial exercise significantly increased (p<0.05) and the peak CK was on Day 4 in three groups, but the recovery times in 3- and 7-group were longer as compared with that in one-group. SPrest (p<0.01) in three groups were significantly elevated from Day 1, and the peak SPrest in one- ,3- and 7-group were on Day 2, Day 3 and Day 4, respectively. OLJ in three groups decreased significantly (p<0.01). OLJ and SPrest in three groups returned to the baseline in 3 days after the peak SPrest. ROM in each group significantly decreased during each exercise period (p<0.01) and these values did not fully returned.

CONCLUSION: The results of this investigation suggest that muscle adaptation can be brought by continuous muscle endurance exercise for three or seven days, but the flexibility of muscle was not returned to the initial level during this study.

749 Board #225 May 29, 2:00 PM - 3:30 PM

High Intensity Aerobic Interval Training Stimulates Muscle Hypertrophy in Young Untrained Subjects

Cassidy Losey, David Thrush, Amy Malinowski, Meredith Piacentini, Stephen Gearhart, Jon Norton, Jake Schick, Eric Salley, Erik Hayes. Taylor University, Upland, IN.

(No relationships reported)

Aerobic exercise (AE) is typically associated with cardiovascular system and metabolic muscle adaptations, but there is potential for changes in muscle size and function as well. Evidence suggests that AE can improve or maintain muscle cross-sectional area (CSA) and/or muscle function in elderly populations, but this has not been observed in young populations. The lack of response in young subjects may be due to an insufficient stimulus to promote muscle growth. High intensity interval training (HIIT) while running may provide a stronger force of contraction than typical long duration AE, which could be the key stimulus for muscular growth, yet this has not been previously examined.

PURPOSE: To examine the impact of 10 weeks of HIIT on skeletal muscle CSA and function in a young adult population.

METHODS: Muscle CSA of the right vastus lateralis (VL) and leg extension speed was assessed before and after 10 weeks of 3x/week HIIT in 12 college-aged subjects. The HIIT protocol consisted of 4 intervals of 4 minutes running at 95% max heart rate (MHR) followed by 4 minutes of recovery at 70% MHR. VL CSA was determined by manual planimetry from panoramic ultrasound imaging and compared to a control group (n=5). Leg extension speed at 40% one repetition maximum was measured with a custom made electronic timing system that utilized an infrared photogate to start and stop a timer as the weight stack ascended 20 cm on the leg extension machine.

RESULTS: VL CSA significantly increased by an average of 9% (P<0.05), while the control group CSA remained unchanged (-2%). Leg extension time increased by an average of 0.09 seconds (0.09s pre vs. 0.18s post) in the HIIT group (P<0.05).

CONCLUSION: To our knowledge, this is the first data showing improvement in whole muscle size in young people with aerobic type training. The increase in leg extension time is consistent with decreases in single muscle fiber power in response to run training previously noted in the literature. Together, these results suggest that high intensity AE may alter skeletal muscle size and/or function in untrained young adult subjects more than previously believed.

Funding: Taylor University Women’s Giving Circle

750 Board #226 May 29, 2:00 PM - 3:30 PM

The Effect Of Cachexia Severity And Resistance Exercise Training On Skeletal Muscle Mass

Justin P. Hardee, Melissa J. Puppa, Aditi A. Narsale, Song Gao, James A. Carson, FACSM. University of South Carolina, Columbia, SC.

(No relationships reported)

Cancer cachexia is a complex wasting syndrome characterized by the progressive loss of skeletal muscle mass. Resistance exercise training’s ability to increase muscle mass and strength make it a potential candidate for non-pharmacological treatments in muscle wasting conditions.

PURPOSE: The purpose of this study was to determine if the severity of cachexia altered resistance exercise training improvements in skeletal muscle mass.

METHODS: At ∼17 weeks of age, male ApcMin/+ mice were subjected to 7 bouts of resistance exercise over a period of 2 weeks. Following the completion of training, mice were stratified based on the percentage of body weight change from peak to post measurements [mild (10%)].

RESULTS: Body weight, tibialis anterior (TA) muscle mass, and testes size decreased during the progression of cachexia. Resistance exercise increased TA muscle mass (10%; p < 0.01) in mice with intermediate cachexia, however this response was not observed with mild cachexia. There was an inverse relationship between training-induced TA mass change and body weight (R2 = -0.60, p = 0.02). In addition, there was an inverse relationship between training-induced TA mass change and testes size (R2 = -0.72, p = 0.007).

CONCLUSIONS: Our results demonstrate that during the progression of cancer cachexia skeletal muscle has the ability to respond to resistance training that consists of eccentric muscle contractions. Additionally, contraction-induced muscle growth was independent of testes size, which emphasizes that these changes can occur while the cachectic environment is present. Resistance exercise training appears to be a potential treatment to attenuate skeletal muscle loss during cancer cachexia. Funded by NCI R01-CA121249

751 Board #227 May 29, 2:00 PM - 3:30 PM

Effects Of A Resistance Training Model On Doxorubicin-induced Muscle Dysfunction In The Rat

Eric C. Bredahl, Keith B. Pfannenstiel, Stephanie E. Greufe, Noah M. Gibson, Colin J. Quinn, Carole M. Schneider, FACSM, Reid Hayward, David S. Hydock. University of Northern Colorado, Greeley, CO.

(No relationships reported)

Doxorubicin (DOX) is an effective chemotherapy treatment that has been associated with a number of deleterious side effects including skeletal muscle dysfunction. Endurance exercise is effective at protecting against a variety DOX-induced toxicities, but examinations of the effects of resistance training on DOX-induced skeletal muscle dysfunction have been limited.

PURPOSE: To examine the effects of a resistance training model in which rats rise to an erect bipedal stance to access food and water on DOX- induced muscle dysfunction.

METHODS: Ten week old male Sprague-Dawley rats were randomly assigned to the raised cage resistance training model (RC) or sedentary (SED) group. RC animals were housed in specialized cages where food and water height were progressively increased so that rats would achieve an erect bipedal stance to access food and water. SED animals were housed in standard rat cages. Following 10 weeks of RC or SED treatments, animals received either a bolus DOX injection (15 mg/kg) or a saline injection (SAL) as a control. Five days following injections, soleus (SOL) and extensor digitorum longus (EDL) function was analyzed ex vivo.

RESULTS: A significant decline in maximal twitch force was observed in SOL and EDL from SED+DOX (-44% and -44%, respectively, P<0.05 vs. SED+SAL), but this significant reduction was not observed in RC+DOX (-22% and -24%, respectively, P>0.05 vs. SED+SAL). Using a 100 s fatigue protocol, a significant reduction in force from baseline was observed at 20 s in SOL from SED+DOX (P<0.05) whereas a significant reduction in force from baseline did not occur until 70 s in RC+DOX (P<0.05).

CONCLUSIONS: The raised cage model employed prior to DOX administration attenuated muscle dysfunction suggesting that resistance exercise may play a role in managing muscle weakness and fatigue often experienced by cancer patients receiving DOX.

752 Board #228 May 29, 2:00 PM - 3:30 PM

Resistance Training Stimulates Protein Synthesis And Attenuates Autophagy Induced By Paradoxical Sleep Deprivation

Marcos Mônico-Neto1, Hanna Karen Moreira Antunes1, Kil Sun Lee1, Sara Quaglia de Campos Giampá1, Helton de Sá Souza1, Murilo Dáttilo1, Alessandra Medeiros1, Wilson Max Almeida Monteiro de Moraes2, Paulo Alexandre Minali3, Marcio Henrique Mello da Luz1, Marcelo Alberti Paiva da Silva1, Sergio Tufik1, Marco Túlio de Mello1. 1Universidade Federal de São Paulo, São Paulo, Brazil. 2Universidade de São Paulo, São Paulo, Brazil. 3Centro de Estudos em Psicobiologia e Exercício, São Paulo, Brazil.

(No relationships reported)

PURPOSE: The purpose of this study was to investigate effects of resistance training (RT) on synthetic and degradation pathways of muscle

proteins in rats that underwent paradoxical sleep deprivation protocol (PSD).

METHODS:Twenty-four male Wistar rats, 3 months old, were equally allocated into four groups: Control (CNTL), Paradoxical sleep deprivation for 96 hours (PSD-96), Resistance training (RT) and Training with subsequent paradoxical sleep deprivation for 96 hours (RT/PSP96). The RT group was submitted to high-intensity resistance training, with progressive load, 5x/week for 8 weeks. Twenty-four hours after the last session of RT, the PSD-96 and RT/PSP96 groups were submitted to PSD for 96 hours using the modified multiple platform method. The animals were euthanized and Plantaris muscle was removed to perform the Proteasome Activity (PA) and western blotting (LC3, p62, phospho-p70S6K). Blood was collected for hormonal assays (total testosterone and IGF-1 plasma). The groups were compared by one-way ANOVA with post-hoc Duncan test, significance p≤0.05.

RESULTS: The blood analysis showed that testosterone and IGF-1 were decreased in PSD-96 and increased in RT when compared with CNTL. Moreover RT performed prior to PSP96 prevented the reduction of these anabolic hormones (F(3, 20)=11.340, p=.00002; F(3,20)=6.0568, p=,00730

respectivity). Increased Phospho-p70S6K was observed only in RT when compared to other groups (F(3, 20)= 3.3664, p=.04156). While RT stimulated PA (F(3, 20)=14.513, p=.00019), PSD-96 promoted autophagy as observed by increased expression of LC3 and p62 when compared to the other groups (F(3, 20)=4.9165, p=.01018; F(3, 20)= 5.5704, p=.00822 respectively). The expression level of LC3 and p62 was restored in RT/PSD-96.

CONCLUSIONS: Our data suggest that PSD activates primarily lysosomal degradation pathways rather than proteassome. RT not only promotes synthetic pathways, but also protects from excessive autophagy induced by PSD. Thus RT is an important strategy to minimize muscle wasting.

753 Board #229 May 29, 2:00 PM - 3:30 PM

Previous Strength Training Episode and Retraining on Muscle Mass and Function after Detraining in Rats

Kijeong Kim1, Kwangseok Hong2, Han-Joon Lee1, Sukho Lee3. 1University of Ulsan, Ulsan, Republic of Korea. 2University of Missouri, Columbia, MO. 3Texas A&M International University, Laredo, TX. (Sponsor: Minsoo Kang, FACSM)

(No relationships reported)

Effects of previous strength training can be long-lived, even after prolonged subsequent inactivity. Traditionally, such “muscle memory” has been attributed to neural factors in the absence of any identified local memory mechanism in the muscle tissue. There is, however, little evidence on the effect of previous strength training and retraining on the skeletal muscle mass and contractile properties after long-term detraining in the animal model.

PURPOSE: To investigate the effects of previous strength training episode and retraining on the skeletal muscle mass and contractile properties after long-term detraining in rats.

METHODS: Twenty four female Sprague-Dawley rats were randomly divided into 4 groups: 1) Control (CON), 2) Detraining (DT), 3) New Training (NT), and 4) Retraining (RT) (n=6 each). The strength training in the DT, NT, and RT consisted of climbing (5 reps/3 sets) a ladder carrying a load suspended from tail during 8 weeks. All rats in the DT underwent detraining for 20 weeks after 8 weeks of strength training. All rats in RT and age matched NT groups underwent 8 weeks of strength training. The contractile properties of the muscle were measured with a Dual Mode Servo and Galvanometer (Model 305, Cambridge Technologies). All data were analyzed using one-way ANOVA with Least Significant Difference post hoc test.

RESULTS: There was a difference in muscle mass of FHL among the training groups (p<0.05). The muscle mass of flexor halluces longus (FHL) in the NT was significantly higher than CON (1.64±0.07 vs. 1.43±0.06 mg; p<0.05). The muscle mass of FHL in the RT was significantly higher compared to the NT (1.91±0.10 vs. 1.64±0.07 mg; p<0.05). However, the isometric tetanic tension (p=0.112) and twitch tension (p=0.169) were not significantly different among the groups.

CONCLUSION: The previous strength training episode may facilitate the increase of muscle mass compared to the subjects for initiating strength training.

754 Board #230 May 29, 2:00 PM - 3:30 PM

Effects Of Overtraining On Muscle Mass-Related Proteins Expression

Andreo F. Aguiar1, Rodrigo Wagner Alves-de-Souza2, Fernanda Regina Carani2, Warlen Piedade2, Maeli Dal-Pai-Silva2. 1North University Of Parana, Londrina, Brazil. 2Sao Paulo State University, Botucatu, Brazil. (Sponsor: Carlo Baldari, FACSM)

(No relationships reported)

Ubiquitin ligase Atrogin1/Muscle Atrophy F-box (MAFbx), myogenic regulatory factors [MRFs (MyoD and myogenin)] and insulin-like growth factor (IGF-I) has been recognized as key regulators of muscle mass in several atrophy models (e.g., disuse, hormonal intervention, and gene knockout). However, its effects on overtraining-induced muscle atrophy remain largely unknown.

PURPOSE: To investigate the effects of overtraining on muscle mass-related proteins expression.

METHODS: Male Wistar rats were randomly assigned to either an overtraining (OT, N = 8) or sedentary (SE, N = 8) group. The OT group was subjected to a 12-wk overtraining protocol (high-intensity exercise with insufficient recovery time between bouts) designed to induce plantaris muscle atrophy. Muscle mass was determined by measurement of cross-sectional area (CSA) of the muscle fibers, and MAFbx, myogenin, MyoD and IGF-I protein expression were measured by Western-blots. Differences between groups for muscle fibers CSA and MAFbx protein expression were determined using a 2-tailed unpaired t-test. The level of significance was set at P ≤ 0.05.

RESULTS: Cross-sectional area (CSA) of the plantaris muscle reduced significantly (P < 0.05) in the OT group compared to SE group. Reciprocally, there was a significant (P < 0.05) 20% increase in MAFbx protein expression, while MyoD (-27%), myogenin (-29%) and IGF-I (-34%) protein expression decreased significantly (P < 0.05) in OT compared to SE group.

CONCLUSION: Our data indicate that overtraining-induced muscle atrophy is associated with upregulation of MAFbx catabolic protein, and downregulation of anabolic proteins (MyoD, myogenin, and IGF-I).

Supported by São Paulo Research Foundation (FAPESP), Proc. 08/52641-1 and the National Council for Scientific and Technological Development (CNPq), Proc. 130628/2008-5.

755 Board #231 May 29, 2:00 PM - 3:30 PM

Molecular Insight into Fast-Twitch Muscle Fiber Remodeling with Taper

Kevin Murach, Ulrika Raue, Brittany Wilkerson, Kiril Minchev, Bozena Jemiolo, James Bagley, Nicholas Luden, Scott Trappe, FACSM. Ball State University, Muncie, IN.

(No relationships reported)

Reduced-volume training (taper) in endurance athletes confers amongst the largest exercise-induced fast-twitch muscle fiber growth rate found in the human literature. MHC IIa hypertrophy at a rate of ∼5% per week along with improved fast fiber power and overall cross-country race performance has been shown in trained runners (n=6, Age=20±1 y, VO2max=70±1 ml·kg-1·min-1) following a 3-week taper. However, molecular-level response to taper in these athletes has only been explored in mixed-muscle and cannot explain fast twitch-specific growth.

PURPOSE: To evaluate fiber type-specific (MHC I and IIa) growth-related gene response following identical pre/post-taper 8 km runs (30:18±0:30 min:sec, 89±1% HRmax) in trained runners.

METHODS: Pre-/4h post-8 km run gastrocnemius muscle biopsies were obtained pre-/post-taper. Fn14, Myostatin, Hsp72, MRF4, MuRF-1, and IGF1 mRNA levels were determined via qPCR.

RESULTS: In MHC IIa fibers, exercise increased Fn14 (P<0.05) and decreased Myostatin (P<0.05) expression post-taper while only Myostatin decreased (P<0.05) pre-taper. In contrast, genes of interest in MHC I fibers remained relatively static post-taper with only an increase in Hsp72 (P<0.05). Exercise decreased Myostatin (P<0.05) and increased MRF4 (P<0.05) pre-taper.

CONCLUSION: The post-taper run increase in Fn14 (strongly correlated to hypertrophy) coupled with favorable mRNA expression of potent negative muscle mass regulator Myostatin provides an initial molecular basis for taper-induced MHC IIa growth in these runners. Characterizing this unique model of exaggerated fast fiber hypertrophy provides new insight into fiber type-specific size regulation with training and taper. Supported by NIH (AG038576)

756 Board #232 May 29, 2:00 PM - 3:30 PM

Substantial Muscle Loss Occurs In The First 5 Days Of Muscle Disuse In Humans

Benjamin T. Wall, Marlou L. Dirks, Tim Snijders, Lex B. Verdijk, Harm Kuipers, Luc JC van Loon. Maastricht University, Maastricht, Netherlands.

(No relationships reported)

It has been well established that disuse leads to a considerable loss of skeletal muscle mass and strength. Most studies have assessed muscle disuse atrophy over ≥14 days and it is currently unknown whether substantial atrophy also occurs during the first few days of muscle

disuse.

PURPOSE: To assess the impact of 5 and 14 days of muscle disuse on skeletal muscle mass and strength.

METHODS: Twenty-four healthy, young (23±1 y) males were subjected to either 5 (n=12) or 14 (n=12) days of one legged knee immobilization using a full leg cast. Three days before and immediately after the immobilization period, a single slice CT-scan was performed to assess quadriceps muscle cross-sectional area. Muscle biopsies were obtained from the vastus lateralis muscle to determine muscle mRNA expression of selected genes implicated in the regulation of muscle mass using real-time PCR. In addition, muscle strength was assessed by 1-RM before and after immobilization.

RESULTS: Quadriceps muscle cross-sectional area declined from baseline by 3.5±0.5 (P<0.0001) and 8.4±2.8 % (P<0.0001), and muscle strength decreased by 8.3±2.3 (P<0.0001) and 22.9±2.6 % (P<0.0001) following 5 and 14 days of immobilization, respectively. Muscle myostatin mRNA expression doubled following immobilization (P<0.05) with no differences between groups. Similarly, MAFBx mRNA expression increased from baseline by a similar magnitude following either 5 (57±14%; P<0.05) or 14 (60±21%; P<0.05) days of muscle disuse, whereas MuRF1 mRNA expression increased significantly only following 5 days of immobilization (59±25%; P<0.05) and remained unchanged after 14 days (+17±18 %; P=0.79).

CONCLUSION: Muscle disuse leads to a rapid loss of muscle mass and strength, with substantial atrophy and changes in associated gene expression already occurring after only 5 days of immobilization. These data suggest that even short periods of muscle disuse, due to illness or injury, are of significant clinical relevance.

757 Board #233 May 29, 2:00 PM - 3:30 PM

Detraining Effect on Satellite Cell Response after Exhaustive Exercise in Thoroughbred Horses

Hirofumi Miyata1, Minako Kawai1, Yoko Imaoka1, Hiroko Aida2, Atushi Hiraga2. 1Yamaguchi Univ., Yamaguchi, Japan. 2Japan Racing Association, Tochigi, Japan.

(No relationships reported)

PURPOSE: Satellite cells are muscle stem cells capable of increasing myonuclear number during repair from injury. The purpose of this study was to investigate the effect of 6-week detraining on the satellite cell activation in Thoroughbred horse muscles.

METHODS: Six horses (3 years old) had acclimatized to exercise on a treadmill before experiments and then were subjected to conventional training for 18 weeks and detraining for 6 weeks. Before (Pre) and after (Post) training (Tr), and after detraining (DTr), an incremental exercise test (IET) was performed on a 6% inclined treadmill to measure maximum oxygen consumption (VO2max) and the velocity at a plasma lactate of 4 mmol/ l (VLA4). Biopsy samples from the gluteus medius muscle were obtained before IET and at 1min, 3 (3h), 6 (6h) and 24 hours (24h) after each IET. Total RNA was extracted from each muscle sample and the levels of Pax7, MyoD, myogenin, PCNA, IGF-I and HGF mRNA expression were determined using real time RT-PCR system.

RESULTS: The mean values of VO2max (ml/ min/ kg) significantly (P<0.05) increased from Pre (144) to Post (164), and decreased in DTr (145). The mean values of VLA4 (ml/ s) also significantly (P<0.05) increased from Pre (7.3) to Post (8.3), and decreased in Dtr (7.3). Compared to values before IET, IL-6 mRNA expression increased remarkably at 6h after IET in Post (2300 hold change), but not in both Pre (260 hold change) and DTr (853 hold change). Myogenin and IGF-I mRNA expressions were significantly (P<0.05) increased at 24h after IET in Post, but not in both Pre and DTr. PCNA mRNA expression had significantly (P<0.05) increased at 24h after IET in all groups. When the correlations between performance level (VO2max and VLA4) and mRNA expressions of each horse were investigated in Pre, the horses with higher VO2max had higher expression levels of MyoD and myogenin mRNAs (r = 0.97 and 0.85). After the 18-week training, interestingly, the horses with higher VLA4 had higher expression levels of myogenin mRNA at 24h after IET (r = 0.86).

CONCLUSION: The activation and proliferation of satellite cells in response to exhaustive exercise differed slightly in Pre-training, Post-training, and detraining for 6 weeks. Our results suggested that the training-induced increase in reactivity of satellite cells had almost disappeared after 6-week detraining.

758 Board #234 May 29, 2:00 PM - 3:30 PM

Muscle Temperature And Fatigue Effects On The Electromechanical Delay Components

Fabio Esposito, Emiliano Cè, Susanna Rampichini, Luca Agnello, Eloisa Limonta, Arsenio Veicsteinas. University of Milan, Milan, Italy.

(No relationships reported)

Neuromuscular activation can be influenced by both muscle temperature (Tm) manipulation and fatigue.

PURPOSE: To assess the effects of Tm manipulation and fatigue on the overall electromechanical delay (EMD) and its electrochemical and mechanical components.

METHODS: Fifteen participants performed voluntary isometric contractions of the elbow flexors at different intensities under neutral (TmN), low (TmL), and high (TmH) Tm, before and after a fatiguing exercise. During contraction, surface electromyogram (EMG) and mechanomyogram (MMG) were recorded from the biceps brachii muscle, together with the force (F) signal. Mean fiber conduction velocity (CV), EMD and the latencies between EMG and MMG (Δt EMG-MMG, which includes the electrochemical processes of EMD) and between MMG and F (Δt MMG-F, which includes the mechanical processes of EMD) were calculated.

RESULTS: TmL increased significantly only Δt EMG-MMG, both before and after fatigue. Fatigue lengthened significantly EMD, Δt EMG-MMG, and Δt MMG-F under all Tm by a similar amount. CV decreased significantly after the fatiguing exercise under all Tm conditions, but to a further extent under TmL.

CONCLUSIONS: During contraction, muscle cooling lengthened the electrochemical but not the mechanical process. This finding, together with the significant CV decrease, is suggestive of a reduction in sarcolemmal propagation properties under TmL. Conversely, fatigue elongated EMD at both the electrochemical and mechanical level to a similar extent under all the investigated Tm. A combined and additional effect of Tm with fatigue was found only on sarcolemmal propagation properties in TmL.

Supported by PUR grant of University of Milan.

759 Board #235 May 29, 2:00 PM - 3:30 PM

Glucose Uptake Heterogeneity during Fatiguing Contractions with Knee Extensor Muscles in Young and Old Men

Thorsten Rudroff1, William C. Klingensmith III2, Brian L. Tracy1, Marco Bucci3, Kari Kalliokoski3. 1Colorado State University, Fort Collins, CO. 2University of Colorado, School of Medicine, Denver, CO. 3University of Turku, Turku, Finland.

(No relationships reported)

Age-related alterations of neuromuscular activation may contribute to increased muscle fatigability. During fatiguing contractions more motor units are recruited and motor unit firing rate increases. However, this knowledge was provided from a very small portion of superficial muscles using intramuscular electromyography (EMG).

PURPOSE: This study used positron-emission-tomography/computer tomography (PET/CT) to estimate spatial heterogeneity of glucose uptake within and among muscles during two types of fatiguing contractions with the knee extensors of young and old men.

METHODS: Six young (26 ± 6 yrs) and six old (77 ± 6 yrs) men performed fatiguing isometric contractions at 25% of maximal voluntary contraction with the knee extensors that required either force or position control with comparable net muscle torque for a similar duration. PET/CT scans were performed immediately after the tasks. Glucose uptake in the quadriceps femoris (QF) was measured using PET and [18F]-2-fluoro-2-deoxy-D-glucose. Within-muscle heterogeneity was determined by calculating the coefficient of variance (CV) of glucose uptake in PET image voxels within the muscle of interest. Among-muscle heterogeneity was expressed as the CV of the mean glucose uptake values for the separate muscles. Standardized glucose uptake values were examined with a two-factor, repeated-measures ANOVA (task x age).

RESULTS: Glucose uptake heterogeneity for the whole QF was similar between young and old men for both fatigue tasks (force control: 40 ± 4 vs. 39 ± 5%, position control: 34 ± 5 vs. 38 ± 8%, P = 0.72). VI showed the greatest glucose uptake heterogeneity during both fatigue tasks in young (42 ± 6 %) and old men (37 ± 8 %) compared with RF (25 ± 3, 28 ± 6%), VM (32 ± 5, 35 ± 7%), and VL (33 ± 9, 30 ± 7%) (P = 0.02). Among-muscle heterogeneity of glucose uptake in QF was similar for force and position tasks of young (22 ± 9, 19 ± 8%) and old men (18 ± 14, 11 ± 3%) (P = 0.57).

CONCLUSION: These data suggest that glucose uptake heterogeneity differs between the QF muscles but is similar for young and old men during two types of fatiguing contractions. We speculate that glucose uptake heterogeneity reflects neuromuscular activation strategies within and among muscles of young and old men.

Supported by NIH/NIA Grant R21 AG033744.

760 Board #236 May 29, 2:00 PM - 3:30 PM

Training Induced Adaptation of Interhemispheric Inhibition

Ryan C.A. Foley, Jayne M. Kalmar. Wilfrid Laurier University, Waterloo, ON, Canada.

(No relationships reported)

Mirror activation is the unintended contraction of contralateral homologous muscles of the opposite hand during a voluntary unimanual contraction. Changes in interhemispheric inhibition (IHI) play a role in the acquisition of unimanual and bimanual tasks.

PURPOSE: The purpose of this study was to determine whether alterations in IHI would contribute to reductions in mirror activation during initial learning and subsequent training of a novel unimanual task.

METHODS: The protocol consisted of alternating right and left hand ramps to 50% maximal index finger abduction force. A task was devised that made force production by the left first dorsal interosseous muscle (FDI) more difficult if there was an unintended contraction of the right FDI. This was achieved by subtracting right force from the left force output. Participants were randomly assigned to a control (CON, n=6) or a training group (TRAIN, n=6). We hypothesized that IHI would increase and mirror activation would decrease after three days of training. Paired-pulse transcranial magnetic stimulation (10ms and 40ms interpulse intervals) was used to quantify IHI of the left motor cortex by the right. IHI was assessed 500ms prior to 5% of maximal contractions of the right FDI.

RESULTS: The TRAIN group, who were told that right force was subtracted from left force, had lower mirror activation than CON at the onset of the first day of training. Lower mirror activation was correlated with higher IHI (r=0.49) at this time point. Mirror activation was higher initially in the CON group but was reduced by 38.0%±39.2% (p=0.03) by the end of the first day, despite the fact that these participants were unaware that mirror activation of the right hand impaired left force output. After the 3 training days, the TRAIN group a further reduction in mirror activation (p=.04) where the CON group had no further reduction. IHI did not change following 3 additional days of training.

CONCLUSION: When participants were aware of the strategy required to maximize force, mirror activation was immediately reduced during this novel unimanual task, possibly due to increased IHI. IHI did not appear to contribute to reductions in mirror activation in the control group.

761 Board #237 May 29, 2:00 PM - 3:30 PM

Motor Unit Activity of Left-Handed Individuals Does Not Differ with Load Type during Fatiguing Contractions

Brice T. Cleland1, Gould R. Jeffrey1, Diba Mani1, Ioannis G. Amiridis2, Roger M. Enoka1. 1University of Colorado Boulder, Boulder, CO. 2Aristotle University of Thessaloniki, Serres, Greece.

(No relationships reported)

The type of load supported by the elbow flexor muscles during fatiguing isometric contractions has been shown to influence endurance time in right-handed individuals (Hunter et al. 2002), with briefer endurance times for tasks requiring position control than for force control. Despite the two load types requiring similar net muscle torques and eliciting similar changes in surface EMG amplitude, Mottram et al. (2005) observed a greater decline in motor unit discharge rate (MUDR) and an increase in discharge variability (CV ISI) during position control compared with force control in right-handed individuals. The difference in endurance time, therefore, was related to the control strategy used during the two tasks. However, Gordon et al. (2012) found that left-handed individuals did not exhibit a consistent relation between endurance times for the two tasks.

PURPOSE: The purpose of this study was to compare the discharge characteristics of motor units in the biceps brachii of left-handed individuals during fatiguing, submaximal, isometric contractions of the elbow flexor muscles involving two different load types.

METHODS: Subjects contracted the elbow flexor muscles to maintain either a constant upward force against a rigid restraint (force task) or a constant elbow angle while supporting an equivalent inertial load (position task) for the same duration (147 ± 81 s) at a mean target force of 24.2 ± 8.3% MVC (range: 6-44% MVC). The tasks were performed in random order at a target force equal to 3.5 % of the maximal voluntary contraction (MVC) force above the recruitment threshold of an identified motor unit.

RESULTS: There was a significant decline in MUDR during both the force task (15.2 ± 4.7 to 12.9 ± 3.5 pps, F = 6.2, P = 0.028) and the position task (14.7 ± 3.8 to 11.6 ± 2.9 pps, F = 35.7, p 0.05). However, there was no difference between the two tasks (t = 0.913, P > 0.05). The CV ISI did not significantly change for either the force task (16.2 ± 3.5 to 16.6 ± 4.7%, F = 0.05, P > 0.05) or the position task (15.5 ± 3.3 to 17.9 ± 4.2%, F = 2.6, P > 0.05), and there was no difference between the two tasks (t = -1.1, P > 0.05).

CONCLUSIONS: Modulation of biceps brachii motor unit activity by left-handed individuals does not differ between sustained contractions that require force and position control.

762 Board #238 May 29, 2:00 PM - 3:30 PM

Hypoxia Induced Reactive Oxygen Species Formation during Contractions in Single Skeletal Muscle Fibers

Li Zuo1, Peter D. Wagner, FACSM2, William J. Roberts1, Amy Shia2, Michael T. Chien3, Michael C. Hogan, FACSM2. 1Oakland University, Rochester, MI. 2University of California, San Diego, La Jolla, CA. 3Kalamazoo College, Kalamazoo, MI. (Sponsor: Mike Hogan, FACSM)

(No relationships reported)

Contractions in whole skeletal muscle during hypoxia have been shown to generate elevated levels of reactive oxygen species (ROS). However, identification of ROS generation within isolated single skeletal muscle fibers has not been studied during reduced oxygen conditions.

PURPOSE: We used Xenopus laevis muscle to test the hypothesis that intracellular ROS generation in single contracting skeletal myofibers increases during hypoxia compared to normoxia.

METHODS: Dihydrofluorescein was loaded into the single fibers and its fluorescence was used to monitor ROS in real-time using confocal microscopy. Each myofiber was exposed to two different maximal tetanic contractile periods (1 contraction/3 s for 2 min, separated by a 60-min rest period) each consisting of one of four different perfusate treatments including high PO2 (30 Torr), low PO2 (3-5 Torr), high PO2 with ebselen, or low PO2 with ebselen at 20°C. Ebselen (an antioxidant) was administered in the perfusate (10 μM) before the designated contractile period.

RESULTS: ROS formation during the low PO2 treatment was significantly higher than the high PO2 treatment, and ebselen substantially decreased ROS generation in both low and high PO2 conditions (P < 0.05). Intracellular ROS accumulated at a faster rate in low vs. high PO2. Force was reduced >30% for each condition except for low PO2 with ebselen, which only decreased ∼15%.

CONCLUSION: These results demonstrate that single myofibers under low PO2 conditions develop accelerated and more severe oxidative stress than under high PO2. Ebselen decreases ROS in both low and high PO2, but only mitigates skeletal muscle dysfunction during reduced PO2 conditions.

Supported by NIAMS Grant AR040155

763 Board #239 May 29, 2:00 PM - 3:30 PM

Sodium Nitrite Incubation at Physiological PO2 Increases Fatigue Resistance in Intact Single Mouse Fibers

Leonardo Nogueira1, Stephen J. Bailey2, Amy A. Shiah1, Paulo G. Gandra1, Michael C. Hogan, FACSM1. 1University of California San Diego, La Jolla, CA. 2University of Exeter, Exeter, United Kingdom. (Sponsor: Michael C. Hogan, FACSM)

(No relationships reported)

Dietary nitrate (NO3-) supplementation has been shown to enhance endurance performance and to increase skeletal muscle Ca2+-release. These effects are believed to be mediated by an increase in blood and tissue nitrite (NO2-).

PURPOSE: To investigate whether NO2- treatment influences skeletal muscle force and fatigue resistance at near-physiological oxygen tensions (PO2).

METHODS: Intact single mouse fibers (FDB muscle) were perfused with Tyrode’s solution (22°C) pre-equilibrated at ambient PO2 (∼156 Torr, n=4) or at a PO2 more physiological to contracting myofibers (15.6 ± 0.01 Torr, n=14) during the whole experimental procedure. Fibers were stimulated at different frequencies (1-150 Hz, Force Frequency curve; FF) followed by repetitive contractions (100 Hz) until fatigue (50% of initial tension; fatigue protocol). After the first FF curve and fatigue protocol, fibers rested for 1hr in the absence or presence of 100 μM NaNO2 and the FF curve and fatigue protocol were repeated. Intracellular pH and fatigue resistance were measured at 15 Torr in a separate group of fibers (n=5) loaded with BCECF and perfused with a modified Tyrode’s solution with and without NaNO2.

RESULTS: Maximal tetanic tension was not changed by NO2- between the first and the second contractile protocols. Submaximal tension was not different at 15 Torr between the two FF curves (n=4), but was significantly lower with NO2- (n=14, P<0.01). At ambient PO2, NO2- incubation significantly reduced the time to fatigue when compared to the first fatigue protocol (n=4, P<0.05). Time to fatigue at 15 Torr was not different between fatigue protocols when NO2- was absent (n=4), but treatment with 100 μM NO2- significantly increased the time to fatigue (∼20%, n=14, P<0.01). Intracellular pH was not different at the same fatigue time-points of the control (n=5) vs. the NO2-, but was significantly lower at the fatigue end point.

CONCLUSION: Acute NaNO2 treatment increased skeletal muscle fatigue resistance at near-physiological PO2 without affecting muscle pH. These data suggest that increasing skeletal muscle exposure to NO2- improves skeletal muscle fatigue resistance (consistent with findings after dietary NO3- supplementation) and allowed a lower pH to be achieved at the fatigue end point. Supported by NIH grant AR040155-17.

764 Board #240 May 29, 2:00 PM - 3:30 PM

Neuromuscular Fatigue, Reserve, and Recovery Following Exhaustive High-Intensity Endurance Exercise

Steven J. Elmer, Camden S. Marshall, Markus Amann, James C. Martin, FACSM. University of Utah, Salt Lake City, UT.

(No relationships reported)

Numerous studies focus on changes in neuromuscular function induced via high-intensity endurance exercise. One potential limitation to the assessment of exercise-induced changes in locomotor muscle function is that considerable time is often required to reposition the participant and/or change equipment between the end of the fatigue task and post-exercise measurements. Thus, substantial recovery may occur resulting in an underestimation of fatigue.

PURPOSE: To evaluate exercise-induced changes in maximum cycling power (Pmax) immediately following exhaustive high-intensity cycling.

METHODS: On separate days, four cyclists performed maximal isokinetic cycling trials (3 s, 90 rpm) before and again 0, 0.25, 0.75, 2.0, 3.3 , 6.6, and 10 min after either a isokinetic cycling time trial (TT, 10 min, 90 rpm) or isokinetic constant power cycling until task failure (Tlim, 100% of TT power, 10.1 min, 90 rpm). Fatigue was estimated by comparing exercise-induced changes in Pmax.

RESULTS: Power produced during TT and Tlim did not differ (310 ± 8 vs. 315 ± 4 W, P = 0.67). Exercise-induced alterations in Pmax were similar following TT and Tlim (cycling trial x time interaction, P = 0.97) and thus pooled values are reported below. Compared to pre-exercise, post-exercise Pmax was reduced by 38 ± 6% immediately following TT and Tlim (1069 ± 29 vs. 662 ± 59 W, P < 0.01). However, at 3.3 min post-exercise, Pmax did not differ from pre-exercise (987 ± 12 vs. 1069 ± 29 W, P = 0.13). Immediate post-exercise Pmax (662 ± 59 W) was more than twice as high as the power produced during the final 3 s of the TT (321 ± 16 W, P < 0.01) as well as the power that elicited Tlim task failure (315 ± 4 W, P < 0.05).

CONCLUSION: Our results demonstrate that exhaustive high-intensity cycling substantially compromises Pmax and recovery of this impaired function occurs within a few minutes. Such rapid recovery may be linked to PCr resynthesis. These results, which highlight the recovery of brief maximal voluntary neuromuscular function, contrast with previous reports of long lasting low-frequency fatigue evaluated via pre- to post-exercise changes in quadriceps potentiated twitch force. Even with considerable fatigue participants were able to produce substantially greater power after TT and Tlim, thus indicating a “reserve capacity” which has been a recent topic of debate.

765 Board #241 May 29, 2:00 PM - 3:30 PM

Effect Of A 103-km Mountain Trail-running Race On Neuromuscular Function

John Temesi1, Thomas Rupp2, Samuel Verges2, Guillaume Y. Millet3. 1Université de Lyon, St-Etienne, France. 2INSERM / Université Joseph Fourier, Grenoble, France. 3Université de Lyon / INSERM, St-Etienne, France.

(No relationships reported)

Ultra-endurance trail-running events drive participants to their physical and mental limits. The well-established central deficits in these events are not fully understood. The use of transcranial magnetic stimulation (TMS) in conjunction with peripheral neural stimulation provides greater detail as to the source of central changes, specifically the differentiation between voluntary activation measured at the cortical (VAc) and peripheral (VAp) levels.

PURPOSE: To determine the effects of a 103-km ultra-trail on neuromuscular functioning, including central and corticospinal fatigue.

METHODS: Neuromuscular function was evaluated before and after a long-duration race (20:24:53 ± 3:26:17) in 24 experienced endurance trail runners (13 men, 11 women; 42 ± 9 years; 66 ± 10 kg; VO2max: 56 ± 7 ml·min-1·kg-1). Tests consisted of maximal voluntary isometric contractions (MVC) of the knee extensors and electrical stimulation of the femoral nerve (single and paired stimuli at 100 and 10 Hz) at rest and during MVC to assess VAp. TMS was also delivered during sets of voluntary isometric contractions at 100, 75 and 50% MVC to calculate estimated resting twitch and VAc.

RESULTS: There was a 34% decrease in MVC post-race (p<0.001). This coincided with decreased VAc (93 to 80%) and VAp (91 to 72%) (both p<0.001). TMS estimated resting twitch amplitude did not change (p=0.09). Peripheral (potentiated) twitch and doublet (100 and 10 Hz) amplitude decreased by 9, 6 and 11%, respectively (p<0.05). The resulting low-frequency/high-frequency ratio decreased by 6% (p<0.05).

CONCLUSIONS: The changes in VA measured cortically and peripherally indicate a critical inability of the corticospinal pathway to drive the muscles. The eccentric nature of ultra-trail running caused peripheral perturbations, particularly low-frequency fatigue. These effects were minor compared to the resulting central deficit.

766 Board #242 May 29, 2:00 PM - 3:30 PM

Bone: An Acute Buffer of Plasma Sodium during Exhaustive Exercise?

Tamara Hew-Butler, FACSM1, Kristin J. Stuempfle, FACSM2, Martin D. Hoffman, FACSM3. 1Oakland University, Rochester, MI. 2Gettysburg College, Gettysburg, PA. 3VA Northern California Health Care System and UC Davis Medical Center, Sacramento, CA.

(No relationships reported)

Both hyponatremia (plasma sodium concentration <135mEq/L) and osteopenia have been well-documented in endurance athletes as separate conditions. Bone has been shown to act as a “sodium reservoir” to buffer severe plasma sodium derangements in animal models and recent cross sectional data have suggested a similar inter-relationship in humans with chronic hyponatremia being associated with lower bone densities.

PURPOSE: The purpose of this study was to explore if acute changes in bone mineral content were associated with significant changes in plasma sodium concentration ([Na+]) in runners participating in a 161-km mountain footrace.

METHODS: 18 runners were recruited for this study. Runners were tested immediately pre- and post- race for the following main outcome measures: bone mineral density (dual-energy x-ray absorptiometry; DEXA); plasma [Na+], arginine vasopressin ([AVP]p), and serum aldosterone concentration ([aldosterone]s). Total sodium intake was determined during the race by race diet analysis using Nutritionist Pro.

RESULTS: Six subjects (2 female) finished the race with a mean (±SD) time of 27.0±2.3 hours. All subjects started and finished the race with plasma [Na+] within the normal range (137.7±2.3 and 136.7±1.6mEq/L, pre- and post-race, respectively). Positive correlations were noted for pre- to post-race change (Δ) in total bone mineral content (BMC; grams) versus Δ plasma [Na+] (r=0.99; p<0.0001), and for %Δ lumbar spine bone mineral density versus total sodium intake (mEq/kg) (r=0.93; p<0.001). Changes in [aldosterone]s were positively correlated with: total sodium intake (r=0.84; p<0.05); Δ total BMC (r=0.82; p<0.05); and Δ plasma [Na+]. (r=0.88; p<0.05).

CONCLUSION: A robust association between change in BMC and plasma [Na+] suggests that sodium status and bone density may be symbiotically related during endurance exercise and should be considered in future investigations of athletic osteopenia.

This study was supported by the Western States Endurance Run Foundation

767 Board #243 May 29, 2:00 PM - 3:30 PM

Magnetic Vs. Electrical Stimulation For The Assessment Of Voluntary Activation Of The Quadriceps

Michael A. Tevald, Andrew Raschke, Brian G. Pietrosimone. University of Toledo, Toledo, OH.

(No relationships reported)

Deficits in the voluntarily activation (VA) of the quadriceps muscles have been identified in a variety of clinical populations, and impairments in VA have been identified as a target of rehabilitation. However, the assessment of VA, in which an electrical stimulus is superimposed on a voluntary contraction, is uncomfortable, and may not be feasible in certain clinical populations. Magnetic stimulation (MS), which is more comfortable than electrical stimulation (ES), may be a more acceptable alternative.

PURPOSE: To compare VA obtained using MS and ES, determine the limit of agreement, and to establish the reliability of each method within and across sessions.

METHODS: 12 healthy young men (n = 4) and women (n = 8) participated in 2 sessions separated by 2 weeks. VA during maximal and submaximal (25, 50, 75, 90% of max) contractions of the quadriceps was assessed using the interpolated twitch technique (100Hz doublet pulse; VA = 1 - (superimposed/resting stimulus)) with both ES (over motor points in the thigh) and MS (45 mm figure of 8 coil over the femoral nerve). VA values obtained using the two methods were compared using Wilcoxon signed-rank (maximal) and paired t-tests (submaximal), as well as limits of agreement.

Intraclass correlation coefficients (3, 1) were calculated for each method within a single session and across sessions.

RESULTS: VA values from ES were lower than MS during 25% (MS = 0.45 (0.24),ES 0.29 (0.09); p = 0.04) and 50% contractions (MS = 0.67 (0.12), ES = 0.59 (0.10); p = 0.40), but not 75% (MS = 0.86, ES = 0.79; p = 0.10), 90% (MS = 0.92, ES = 0.86;p = 0.09) or maximal (MS = 0.97 (0.06), ES = 0.93 (0.08); p = 0.10) contractions. Maximal

VA obtained with MS and ES were correlated (r = 0.58, p = 0.04), but within-session limits of agreement were unacceptably large (-0.09 to 0.17). Reliability was good for both methods within a single session (MS ICC = 0.829; ES = 0.794) and acceptable at 2 weeks (MS = 0.753; ES = 0.681). Anecdotally, tolerance for MS was substantially higher than for ES.

CONCLUSION: Our results suggest that MS may be an acceptable alternative to ES for the assessment of maximal VA of the quadriceps. Reliability for VA using both ES and MS is acceptable within and across sessions, although the large limit of agreement suggests the two techniques cannot be used interchangeably.

768 Board #244 May 29, 2:00 PM - 3:30 PM

Rate Of Torque Development Versus Rate Of Velocity Development During Voluntary And Evoked Muscle Actions

Nathaniel D.M. Jenkins1, Ty B. Palmer2, Haley C. Bergstrom1, Kristen C. Cochrane1, Daniel A. Traylor1, Robert W. Lewis1, Joel T. Cramer, FACSM1. 1University of Nebraska-Lincoln, Lincoln, NE. 2Oklahoma State University, Stillwater, OK.

(No relationships reported)

PURPOSE: To compare the rate of torque development (RTD) and rate of velocity development (RVD) during voluntary and evoked isokinetic leg extension muscle actions at 60°s-1.

METHODS: Thirteen men (mean age ± SD = 22 ± 3 years; mass = 77 ± 10 kg) performed three maximal voluntary and three evoked isokinetic leg extension muscle actions at 60°·s-1. The femoral nerve was evoked using a constant current stimulator. Peak torque (PTV and PTE), the electromechanical delay (EMDV and EMDE), and the time to load range (TTLRV and TTLRE) were calculated from the voluntary and evoked contractions, respectively. Voluntary and evoked RTD (RTDV and RTDE, respectively) and RVD (RVDV and RVDE, respectively) were calculated for each 10 ms window from the onset of torque to peak torque and load range, respectively.

RESULTS: The TTLRV was lower (p<0.01) than TTLRE. There was no interaction between RVDV and RVDE across time (p=0.12), but there was an interaction between RTDV and RTDE across time (p<0.01). RTDV was greater (p= 0.03) than RTDE for every 10 ms window except 20-30 ms (p=0.06). Peak RTDV and peak RVDV were correlated with PTV (r=0.66-0.75; p<0.05), but not with each other (r=0.48; p=0.09). PTE was correlated with peak RTDE, peak RVDE, and EMDE (r=-0.59-0.69; p<0.05). Correlations were also found among peak RTDE and peak RVDE (r=0.78; p<0.01) and peak RVDE and EMDE (r=-0.80; p<0.01).

CONCLUSIONS: As expected, RTDV was greater and occurred later than RTDE. Voluntary muscle actions achieved the load range (TTLRV) quicker than evoked (TTLRE), however, RVDV and RVDE were surprisingly similar (Figure 1). If the main physiological difference between voluntary and evoked RTD is rate coding, it is possible that firing rate may not play a major role in RVD as it does with RTD.

769 Board #245 May 29, 2:00 PM - 3:30 PM

The Influence Of Skeletal Muscle MHC Composition On Explosive Force Production In Man

Jonathan P. Folland, FACSM, Adam Fry, Richard A. Ferguson. Loughborough University, Leics, United Kingdom.

(No relationships reported)

Given the well documented influence of myosin heavy chain (MHC) composition on the rate of force development (RFD) of single muscle fibres (Metzger & Moss, 1990), it is surprising that the importance of skeletal muscle composition for explosive force production in man remains unclear.

PURPOSE: To investigate the influence of MHC composition on voluntary and involuntary explosive force production in man.

METHODS: Following familiarisation, 31 healthy untrained young men performed a series of voluntary and involuntary (supramaximally evoked octets (8 pulses at 300 Hz) via electrical nerve stimulation; that drives the muscle at its maximal capacity for force development) explosive isometric contractions of the knee extensors of the dominant leg (joint angles: knee, 120°; hip, 105°) on two occasions 7 days apart. Force was measured with a strain gauge perpendicular to the tibia at 25 ms intervals after force onset, and RFD for each 25 ms interval and peak RFD (PkRFD, 5 ms epoch) determined. Maximum voluntary force (MVF) of the knee extensors was also assessed. Absolute and relative (%MVF) explosive force and RFD were calculated. A muscle biopsy sample was taken from the VL (20 mg) 7 days after the last force measurements, and MHC composition (I, IIA, IIX) determined with SDS-PAGE. Pearson’s correlations were used to assess the strength of relationships.

RESULTS: Absolute voluntary explosive force production (range: 50 ms, 35-338 N; PkRFD, 5.1-20.1 kN/s) and muscle composition (range: MHC I, 21.4-62.6; MHC IIX, 10.2-29.8%) were highly variable between participants. However there were no relationships between voluntary explosive force or RFD, expressed in absolute or relative terms, with any measure of muscle composition. In contrast MHC IIX composition, was correlated with evoked explosive force (r2: 50 ms, 0.35; 75 ms, 0.26; 100 ms 0.24; All P<0.01) and PkRFD (r2: 50 ms, 0.33; P<0.001).

CONCLUSIONS: Muscle composition, specifically the proportion of MHC IIX, was a significant determinant of the maximal intrinsic contractile capacity of the knee extensors for explosive force production during involuntary contractions. However there was no influence of any measure of muscle composition on voluntary explosive force production, and this supports previous findings on the importance of volitional neural drive.

770 Board #246 May 29, 2:00 PM - 3:30 PM

High Concentration CO2-water Immersion To Promote A Recovery From Muscle Fatigue After Submaximal Exercise

Noriyuki Yamamoto1, Tadashi Wada2, Hitoshi Yanagi3, Masaaki Hashimoto4. 1Japanese Red Cross Hokkaido College of Nursing, Kitami, Japan. 2Kokushikan Univ., Tokyo, Japan. 3Kitami Institute of Technology, Kitami, Japan. 4Teikyo. Univ. Sci., Tokyo, Japan.

(No relationships reported)

Clinical observations of CO2-hot spring (CO2 ≥1000 ppm) immersion revealed the effects, i.e. an immersed part reddening, skin blood flow improvements, blood catecholamine decrease, etc. In response to the CO2-water bath, the reduction of sympathetic nerve activity indicating stress may imply the facilitation of muscle fatigue recovery.

PURPOSE: The present study was investigated whether an immersion into the CO2-water after submaximal exercise could facilitate a recovery from muscle fatigue.

METHODS: Six male healthy students (Age; 21-22 yrs) performed 10 min pedaling exercise at 60% Vo2max were given one of the following 3 treatments in a different day; immersion into tap-water (CO2<20 ppm) or artificial CO2-water (CO2>1000 ppm) (30 °C, 10 min), or dry bathtub sitting rest (air) after exercise. Blood flow in the immersed skin (BF) and electrocardiogram (ECG) were recorded continuously throughout the experiment. Cardiac autonomic nerve activity was evaluated by R-R interval fluctuation power spectrum analysis (PSA) using ECG. Muscles stiffness (right vastus lateralis dominant; MS), blood lactate concentration (BLa), salivary cortisol (SCo), visual alanogue scale in muscle fatigue (VAS) were evaluated at pre-exercise, immediately after exercise, during immersion (at 5 min of immersion, not measured MS) and at 10 min after the end of immersion.

RESULTS: At 10 min after immersion, MS in CO2-water treatment was significantly small (22.2±1.2 tone, p<0.01) compared with air(28.0±2.0 tone)and tap-water immersion(31.8±2.2tone). In CO2-water immersion, BLa was significantly decreased compared with air (4.3±1.6 vs 3.7±1.7 mmol·l-1, p<0.05), while the other 2 treatments did not affect. A power ratio, LF(0.04∼0.15Hz)/HF(0.2∼0.4Hz), in PSA was smaller in CO2-water treatment than in tap-water treatment. Compared with the air, SCo was significantly decreased in tap (24%) and CO2-water immersion (48%).

CONCLUSIONS: The present study suggested that the recovery of increased sympathetic nerve activity and muscle stiffness were facilitated by CO2-water immersion after submaximal exercise. CO2-water immersion might relax the muscle through some CNS mechanism and improve a muscle blood flow, thus resulting in a promotion of recovery from fatigue.

771 Board #247 May 29, 2:00 PM - 3:30 PM

A Mitochondrial Targeted Antioxidant Improves Force-recovery After Fatigue In Intact Single Myofibers At Low Po2

Paulo G. Gandra, Leonardo Nogueira, Amy A. Shiah, Michael C. Hogan, FACSM. UCSD, San Diego, CA.

(No relationships reported)

Fatigue due to repetitive contractions in skeletal muscle results in force depression and altered Ca2+ handling. Ca2+ handling and sensitivity in myofibers are known to be partially modulated by reactive oxygen species (ROS). Since ROS generation is enhanced by contractile activity and by low intracellular PO2, we hypothesized that ROS might play a role in muscle recovery after fatiguing contractions.

PURPOSE: Test if the mitochondrial targeted antioxidant SS31 alters Ca2+ transients and myofibril Ca2+ sensitivity after fatigue at low extracellular PO2.

METHODS: Intact single myofibers from mouse FDB muscle were injected with the fluorescent probe Fura-2 to follow the changes in intracellular Ca2+ during contractions. Fibers were kept at a PO2 of ∼4 Torr starting 30 min before and throughout the duration of the experiments. A group of fibers was treated with the antioxidant SS31 (1 uM) 60 min before the start of the experiments (n = 4) while control fibers were perfused with regular solution (n = 4). Contractile tension and Fura-2 signals at submaximal (30 and 50 Hz) and at maximal (100 Hz) stimulation frequencies were measured before and 30min after the induction of fatigue by repetitive tetanic contractions (40% decrease in initial tension).

RESULTS: The relative Fura-2 fluorescence signal during contractions (30 min after fatigue/before fatigue) was not different between control (30 Hz = 0.88 ± 0.02; 50 Hz = 0.90 ± 0.016 and 100 Hz = 0.85 ± 0.03) and SS31 treated fibers (30 Hz = 0.89 ± 0.05; 50 Hz = 0.92 ± 0.03 and 100 Hz = 0.89 ± 0.03). However relative submaximal tension, 30min after fatigue/before fatigue, was higher in fibers treated with SS31 (30 Hz: 0.79 ± 0.09 vs. 0.43 ± 0.10 and 50 Hz: 0.89 ± 0.04 vs. 0.50 ± 0.14 for SS31 and control respectively; P<0.05). The enhanced recovery of tension at low frequencies of stimulation with SS31 without a significant difference in peak Ca2+ transients during submaximal contractions between groups suggests an increase in myofilament Ca2+ sensitivity after fatigue with SS31 compared to control.

CONCLUSIONS: Mitochondrial ROS generation may play an important role in decreasing myofilament Ca2+ sensitivity during and after fatigue in skeletal muscle fibers under low PO2, and mitochondrial targeted antioxidants appear to be beneficial in the recovery process. Supported by NIH AR040155

772 Board #248 May 29, 2:00 PM - 3:30 PM

Mechanisms Of Itch Evoked By The Muscle Building Supplement Beta-alanine

Qin Liu1, Chao Ma2, Parul Sikand2, Zimin Liu3, Zongxiang Tang4, Liang Han4, Shuohao Sun4, Robert H. LaMotte2, Xinzhong Dong5. 1Washington University in St Louis, St Louis, MO. 2Yale University School of Medicine, New Haven, CT. 3Natural Alternatives Int’l, San Marcos, CA. 4Johns Hopkins University School of Medicine, Baltimore, MD. 5Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD.

(No relationships reported)

Beta-alanine is one of the few naturally occurring beta amino acids occurring in humans. In combination with L-histidine, beta-alanine forms the dipeptide carnosine found in high concentrations in several tissues including muscle where it functions as an intracellular buffer. Beta-alanine is a widely used as a dietary supplement to increase intramuscular carnosine synthesis, in an attempt to improve exercise performance by delaying the onset of pH induced peripheral muscle fatigue. The most common side effect of beta-alanine is a tingling of the skin and itch which is apparent above a single dose of 10mg per kg body mass, although symptoms may be attenuated with higher doses where a sustained release formulation of beta-alanine is used.

PURPOSE: To determine the underlying molecular mechanism responsible for the symptoms of tingling and itch. Methods &

RESULTS: Beta-alanine is a putative ligand for several receptors including MrgprD, a G protein-coupled receptor specifically expressed in a subpopulation of primary sensory neurons that exclusively innervate skin. Using mouse behavioral assays and human psychophysical data we have been able to demonstrate that beta-alanine’s site of action is the skin and that MrgprD receptors are required for beta-alanine induced itch. In vivo electrophysiological recording and in vitro Ca2+ imaging show that a highly restricted subset of MrgprD+ DRG neurons is directly activated by beta-alanine. This subset is mechanically sensitive and completely segregated from the histamine-responsive population, and may be the long-sought mechanically sensitive itch-detecting neurons.

CONCLUSION: MrgprD functions as an itch receptor and mediates non-histaminergic itch induced by beta-alanine. The primary sensory neurons responsive to beta-alanine are likely part of a histamine-independent itch neural circuit and a target for treating clinical itch that is unrelieved by anti-histamines.

773 Board #249 May 29, 2:00 PM - 3:30 PM

The Effects of Dietary Cholesterol and Resistance Training as Countermeasures to Accelerated Muscle Loss

Teak V. Lee, Steve Bui, Chang Woock Lee, Vincent C.W. Chen, James D. Fluckey, Steven E. Riechman, FACSM. Texas A&M University, College Station, TX.

(No relationships reported)

Hindlimb unloading (HU) is an animal paradigm known to induce atrophy of skeletal muscle. Resistance exercise training (RET) has been reported to attenuate, but not completely prevent this muscle loss. Greater cholesterol (Chol) intake has been associated with higher lean mass accretion in older adults performing RET. Thus, increased Chol intake may be a potential countermeasure.

PURPOSE: To determine the efficacy of dietary Chol & RET as countermeasures to muscle atrophy induced by unloading.

METHODS: Thirty-three adult male Sprague-Dawley rats were randomly assigned to 1 of 6 groups: cage control (CC), CC+Chol, HU, HU+Chol, HU+RET or HU+RET+Chol. Animals with the Chol designation were given diets similar to the other groups but with 10 times the level of cholesterol. Rats in the HU groups were tail suspended for 28 days. RET consisted of a progressive program involving weighted jump squats 3 d/wk for 4 wk. At baseline, day 14, & day 26, body composition was assessed by DEXA. On day 28, animals were euthanized & plantar flexor muscles were harvested.

RESULTS: After 28 days of HU, body mass from the HU+RE+Chol group was lower (P < .001) than the CC group. Both soleus to body mass & gastrocnemius to body mass ratios in the HU groups were less (P < .001) than the CC groups, but not different between HU groups. Similarly, DEXA analysis showed decreases in whole body lean mass (P < .001) in the HU groups when compared to the CC groups.

CONCLUSION: These data suggest that the dietary Chol or RET used in this study may not be sufficient to overcome the deleterious effects of HU.

Values are mean ± SD

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*Denotes significant difference from CC groups (p < .001)

Supported by ACSM, NASA, Huffines Institute for Sports Medicine and Human Performance, TACSM, TAMU HLKN & CEHD, & NSBRI.

774 Board #250 May 29, 2:00 PM - 3:30 PM

Acupuncture or Herb Medicine Can Increase in Muscle Strength in Resistance Training in Rats

Sukho Lee1, Kijeong Kim2, Junyoung Hong1, Aram Yoon1, Joon Young Park3. 1Texas A & M International University, Laredo, TX. 2University of Ulsan, Ulsan, Republic of Korea. 3Temple University, Philadelphia, PA. (Sponsor: Dr. Minsoo Kang, FACSM)

(No relationships reported)

Muscle hypertrophy, increase in size of muscle, has become a major concern for athletes to improve performance, for elderly to prevent/attenuate age-related muscle atrophy and for patients to rehabilitate from injury. Electroacupuncture and herb have been widely used as therapeutic interventions that control pain under pathological conditions.

PURPOSE: To investigate the effect of acupuncture and/or herbal medicine on muscle contractile properties in resistant trained rats. METHODS Forty female Sprague Dawley rats were randomly divided into 5 groups: 1) Control (CON), 2) Resistance Training (RT), 3) RT+Herb (RTH), 4) RT+Acupuncture (RTA), and 5) RT+Combination of two treatments (RTC) (n=8 each). Resistant training was performed every other day for 8 weeks using ladder climbing. Huang Qi (Radix Astragali Membranceus) was given via oral gavage technique once a day for 8 weeks (1 ml mixed with water based on concentration of 368 mg/kg). Sparse-wave Electro-Acupuncture treatment (2-15 Hz, 2-4 Voltage for 15 min) was applied by needling ST36 and GB34 3 times/wk for 8 weeks. All rats received sham treatment same as treatment groups. All data were analyzed using One-way ANOVA with Least Significant Difference post hoc test.

RESULTS: The muscle mass of flexor halluces longus (FHL) was significantly increased in all treatment groups compared to CON (p< .05). The isometric twitch (Pt) and tetanic tension (Po) of FHL in RTH and RTA were significantly higher compared to CON and RT (p< .05).

*: p< .05 from CON. #: p< .05 from RT

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CONCLUSION: The acupuncture and herbal medicine can be used as effective therapeutic interventions for increasing in muscle strength combined with resistant training.

775 Board #251 May 29, 2:00 PM - 3:30 PM

The Effect of Herbal Diet on Skeletal Muscle Mass After Resistance Training in Rats

Junyoung Hong1, Kijeong Kim2, Aram Yoon1, Joon Young Park3, Sukho Lee1. 1Texas A & M International University, Laredo, TX. 2University of Ulsan, Ulsan, Republic of Korea. 3Temple University, Philadelphia, PA. (Sponsor: Minsoo Kang, FACSM)

(No relationships reported)

Resistance training has been well established as an effective strategy for muscle hypertrophy, increase in skeletal muscle mass and strength. Herbal diet has been introduced as an alternative treatment to alleviate muscle atrophy and therapeutic intervention. However, there is little evidence on the effect of herbal diet on skeletal muscle mass.

PURPOSE: To investigate whether herbal diet affects skeletal muscle mass after resistance training in rats.

METHODS: Twenty-four rats were randomly divided into 3 groups: 1) Control (CON, n=8), 2) Resistance training (RT, n=8), 3) RT+Herb (RTH, n=8). Resistance training was performed every other day for 8 weeks using ladder climbing. The ladder climbing exercise consisted of 3 sets of 5 repetitions with a 1 min rest interval between the repetitions and a 2 min rest between the sets. Huang Qi (Radix Astragali Membranceus) was given via oral gavage once a day for 8 weeks (1 ml mixed with water based on concentration of 368 mg/kg). All rats received sham treatment, same as treatment groups. All data were analyzed using One-way ANOVA.

RESULTS: After 8 weeks of interventions, muscle mass of Gastrocnemius, Plantaris, and Flexor hallucis longus showed significant increases in RT and RTH groups compared to CON (p<.05). However, there was no significant difference between RT and RTH groups.

CONCLUSION: Resistance training was considered as effective treatment for augmentation of muscle mass. However, combination of RT with herbal diet did not induce an additive effect on skeletal muscle hypertrophy.

776 Board #252 May 29, 2:00 PM - 3:30 PM

Effect of Acupuncture on Skeletal Muscle Mass After Resistance Training in Rats

Aram Yoon1, Kijeong Kim2, Junyoung Hong1, Joon Young Park3, Sukho Lee1. 1Texas A & M International University, Laredo, TX. 2University of Ulsan, Ulsan, Republic of Korea. 3Temple University, Philadelphia, PA. (Sponsor: Minsoo Kang, FACSM)

(No relationships reported)

Hypertrophy of skeletal muscle has become of great interest to elderly people, elite power athletes, and patients rehabilitating from injury. Because decrease in muscle mass and strength is associated with several health problems, maintaining proper muscle mass and strength has been an essential factor that impacts the quality of life. Acupuncture, as an alternative therapy for muscle atrophy, has a beneficial effect although the underlying mechanisms therein remain uncertain. The present study investigated whether or not acupuncture treatment affected muscle hypertrophy in resistance training rat.

PURPOSE: To investigate the effect of acupuncture on skeletal muscle mass after resistant training in rats.

METHODS: Twenty four Sprague-Dawley rats were randomly divided into 3 groups; 1) Control (CON, n=8), 2) Resistant Training (RT, n=8), 3) RT+Acupuncture (RTA, n=8). Resistance training consisted of 3 sets of 5 repetitions using ladder climbing exercise. The initial weight attached was 50% of their body weight and increased gradually throughout the 8 weeks. Sparse-wave electro-acupuncture treatment with 2-15 Hz, 4-6 Voltage was applied by needling at acupoints, Zusanli (ST36), and Yanglingquan (GB34), 3 times per week for 8 weeks. Grip strength was measured and hindlimb muscles were harvested and measured the wet weight.

RESULTS: There were no significant differences in body weight among groups. Muscle mass of hindlimb (Gastrocnemius (9.2%), Plantaris (12.6%), and Flexor hallucis longus (32.3%)) were significantly increased by 8 weeks of resistance training (p<.05). Muscle mass of tibialis anterior was significantly increased (14.3%) only by acupuncture treatment (p<.05). Grip strength was significantly higher in RTA than CON and RT (p<.05).

CONCLUSION: Resistance training induces muscle hypertrophy in several muscle groups while acupuncture results in muscle hypertrophy only in the tibialis anterior muscle. Acupuncture itself seems to have a restrictive effect on muscle hypertrophy considering that the acupoint of ST36 and GB 34 were located at the tibialis anterior muscle.

777 Board #253 May 29, 2:00 PM - 3:30 PM

Potassium Channel Blocker DAP Increases Muscular Work During Cyclic Contractions

John McDaniel1, Michelle Moyer2, Erik Van Lunteren2. 1Kent State University, Kent, OH. 2Louis Stokes VA Medical Center, Cleveland, OH. (Sponsor: James C Martin, FACSM)

(No relationships reported)

BACKGROUND: Previous investigators have reported 3,4-Diaminopyridine (DAP) to be an effective aminopryidine at blocking voltage gated K channels and increasing muscle force production during isometric contractions. As a result DAP is used to treat various neuromuscular disorders and may serve as a method to optimize force production during functional electrical stimulation in spinal cord injured subjects. Most voluntary actions, however, are repetitive in nature and require the muscle to produce force while shortening and relax during passive lengthening. Thus utilizing workloops to measure work during cyclic contractions may provide insight into the benefits of DAP during normal voluntary activities such as ventilation and locomotion.

PURPOSE: The purpose of this investigation is to determine the influence of DAP on work produced during cyclic muscle contraction using an in-vitro workloop technique.

METHODS: Diaphragm muscles strips from Sprague-Dawely rats were placed in a Kreb solution bath and mounted to a dual control servo motor. The muscles were subjected to a series of 250 ms isometric tetanic contractions and 1 and 3 Hz workloops using stimulation frequencies of 25, 50 and 75 Hz. This protocol was repeated following the addition of DAP into the bath such that the final bath concentration of DAP was 0.3mM.

RESULTS: Isometric force increased following the administration of DAP for the 25 Hz (35%) and 50 Hz (17%) stimulation frequencies but not 75 Hz stimulation frequency. Work performed by the muscle increased during both 1 and 3 Hz workloops and across all stimulation frequencies (95%, 26% and 5% for 25, 50 and 75 Hz respectively). Furthermore, the addition of DAP gave the muscle the ability to perform the same amount of work at 25Hz stimulation frequency as it would otherwise at 50Hz stimulation frequency.

CONCLUSIONS: These data indicate that DAP has a greater influence on cyclic work compared to isometric force. Furthermore, in regards to functional electrical stimulation, the addition of DAP may allow stimulation frequencies to be reduced by 50% while achieving the same muscular work.

778 Board #254 May 29, 2:00 PM - 3:30 PM

Interaction Of Mitochondrial Proteins With Myoglobin In C2C12, Mouse Skeletal Muscle Cells

Tatsuya Yamada1, Nobumasa Iwanaka2, Takeshi Hashimoto2, Thomas Jue3, Kazumi Masuda1. 1Kanazawa University, Kanazawa, Japan. 2Ritsumeikan University, Kusatsu, Japan. 3University of California Davis, Davis, CA.

(No relationships reported)

PURPOSE: Most physiologists envision myoglobin (Mb), a muscle specific oxygen binding protein, is as a cytosolic protein. However, our recent immunohistochemical and biochemical analyses have shown that Mb locates in both the cytosol and the mitochondria and that the mitochondrial Mb content correlates positively with the muscle capacity for oxidative metabolism. These results have led us to the hypothesis that mitochondrial Mb may have a direct role in the regulating mitochondrial respiration. In order to assess this idea, we have determined protein-protein interaction between Mb and mitochondrial proteins in C2C12 skeletal myocytes in the present study.

METHODS: C2C12 myoblasts were cultured with proliferation medium (DMEM with 10% FBS) primarily, then they were differentiated to myotube by DMEM with 2% DBS. Cellular subfractions were separated by serial centrifugation, and western blotting (WB) assessed the presence of Mb protein in each fraction. Co-immunoprecipitation (Co-IP) was performed to confirm protein-protein interactions of Mb with mitochondrial proteins.

RESULTS: WB confirmed the presence of Mb protein in mitochondrial fraction in C2C12 myotube, which were not cytosolic contaminants. Both mitochondrial outer membrane protein VDAC and inner membrane protein COX-IV were detected from only the mitochondrial fraction. COX-IV co-immunoprecipitated with Mb, showed by Co-IP assay that revealed Mb detection in the immunoprecipitates of COX-IV and COX-IV detection in the immunoprecipitates of Mb. These results suggested that there was a Mb and COX-IV interaction in C2C12 myotube.

CONCLUSIONS: The present results suggested the potential interaction of mitochondrial respiratory chain protein with Mb in mouse skeletal myocytes. Further study, including proteome analysis, will help to determine the mechanism for the interaction between mitochondrial proteins and Mb.

© 2013 American College of Sports Medicine

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