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A-34 Free Communication/Poster - Aging: Maturation

Medicine & Science in Sports & Exercise: May 2013 - Volume 45 - Issue 5S - p 20–24
doi: 10.1249/01.mss.0000433609.36179.14

May 29, 2013, 7:30 AM - 12:30 PM

Room: Hall C

149 Board #1 May 29, 9:30 AM - 11:00 AM

Aging, Not Inactivity, Alters Lactate Metabolic Properties To Facilitate Lactate Oxidation In Fast-type Skeletal Muscle

Sadayoshi Taguchi, FACSM. Ritsumeikan University, Kusatsu, Japan.

(No relationships reported)

PURPOSE: The present study focused on the metabolic properties involved in lactate shuttle in slow-type and fast-type skeletal muscles from aged rats, including monocarboxylate transporter (MCT) 1 and MCT4, to explore the mechanisms for greater fatigue resistance and less lactate accumulation during prolonged muscle contraction in old rats.

METHODS: Soleus (SOL) and extensor digitorum longus (EDL) muscles were obtained from old rats, young and hindlimb-suspended rats, and young control rats. Protein expression of MCT1 and MCT4 and enzymatic activities of glycolysis and mitochondrial oxidation were measured.

RESULTS: MCT1 expression was lower in SOL from of old rats than that from young control and young suspension groups. MCT4 expression was also lower in EDL from old rats than in that of young control and young suspension group. The ratio of lactate dehydrogenase to citrate synthase activities was lower in SOL from young control than that from old and young suspension groups. In EDL, the ratio was lower in old group than in young control and young suspension groups.

CONCLUSION: Aging can change metabolic properties in skeletal muscle to facilitate lactate oxidation in fast-type muscle and can increase fatigue resistance. These changes are as a consequence of aging rather than of inactivity.

150 Board #2 May 29, 9:30 AM - 11:00 AM

Exercise Increases Insulin Sensitivity Related To Aging By Decreasing Ptp1b Expression In Rat Skeletal Muscle

Amanda Christine Silva Sponton1, Leandro Moura1, Luciana Pauli2, Eduardo Ropelle2, Dennys Cintra2, Adelino Silva3, Barbara Rodrigues2, Maria Alice Mello1, José Rodrigo Pauli4. 1São Paulo State University, Rio Claro, Brazil. 2Campinas University State, Campinas, Brazil. 3São Paulo University, São Paulo, Brazil. 4Campinas University State, Campinas, Brazil.

(No relationships reported)

Introduction: Naturally, aging leads to pro-inflammatory condition which contributes to insulin resistance.

PURPOSE: The present study investigated the effects of physical exercise on pro-inflammatory proteins and insulin signaling in skeletal muscle of elderly rodents.

METHODS: For this, Wistar rats were divided into 3 groups: control (C) 3 months old, Elderly Sedentary (ES) and Trained (ET) aged 27 months old. The ET group was submitted to two sessions of 45 minutes of exercise with 30 minutes interval between them. The body weight, epididymal fat, insulin sensitivity (Kitt), glucose and insulin were analyzed. In skeletal muscle (gastrocnemius) activity of the insulin signaling pathway such as the analysis of insulin receptor (IR), insulin receptor substrate 1 (IRS-1) and protein kinase B (Akt) were analyzed. Still in the gastrocnemius muscle protein expression of phosphatase 1B (PTP1B), and Sirtuin 1 (SIRT-1) was observed.

RESULTS: The results show that acute exercise did not alter the weight of the animals, but was effective in reducing the inflammatory process of aging and improve insulin sensitivity by improving the activity of key proteins of the signaling cascade via this hormone. Note that the reduction of PTP1B protein in aged animals appears to be related to the increase of SIRT1 after exercise.

CONCLUSION: It is concluded that acute exercise can reduce the inflammatory process related to senescence regardless of body weight reduction.

151 Board #3 May 29, 9:30 AM - 11:00 AM

Weight-bearing Exercise Stimulates Muscle Protein Synthesis In Aged Rats

Hyeong Tae Kwon, Hyo Jeong Kim, Chang Keun Kim. Korea National Sport University, Seoul, Republic of Korea.

(No relationships reported)

PURPOSE: Muscle protein synthesis decreases during aging, but exercise may reverse this trend. The present study was performed to investigate the effect of weight-bearing exercise on aged muscle protein synthesis.

METHODS: Young (12 wk, n=28) and aged (100 wk, n=26) male, Sprague-Dawley rats were randomly assigned to the time course of resistance exercise. Muscle samples were obtained before and during the recovery period of weight-bearing ladder climbing (60-80%1RM, 25-30 climbs/h). PKB/Akt, mTOR, p70S6k, 4E-BP1 and AMPK phosphorylation were measured to analyze muscle protein synthesis rate.

RESULTS: This type of resistance exercise generated a significant increase in mTOR phosphorylation immediately after exercise in aged rats (∼71%, p=.02) and p70S6K was elevated throughout the 3 hrs of recovery (347%, p=.004). On the other hand, Phospho-AMPK (Thr172) tended to be greater in aged rats.

CONCLUSIONS: These results suggest that the intensitive resistance exercise positively effect on muscle protein synthesis in aged skeletal muscle.

152 Board #4 May 29, 9:30 AM - 11:00 AM

Change Of Motor Signaling Pathway With Intensive Endurance Exercise In Aged Skeletal Muscle Of Rats

Hyo Jeong Kim, Chang Keun Kim, Hyeong Tae Kwon. Korea National Sport University, Seoul, Republic of Korea.

(No relationships reported)

PURPOSE: It is generally considered that aerobic training does not result effective muscle hypertrophy. This study was performed to determine the effect of intensive endurance running on muscle protein synthesis in aged skeletal muscle.

METHODS: Young (12wk, n=28) and aged (100 wk, n=28) male Sprague-Dawley rats (n = 56) were randomly assigned to the time course of the treadmill running (75-80% VO2max, 1hr). Muscle samples were obtained before and during the recovery period following exercise from EDL muscle. PKB/Akt, mTOR, p70S6k, 4E-BP1 and AMPK phosphorylation were determined by SDS-PAGE and western blotting.

RESULTS: We confirmed an acute intensive endurance exercise generated significant increase in Akt(∼193%, p=.001), mTOR(∼206%, p=.001) and p70S6K(∼447%, p=.001) phosphorylation immediately after exercise and the increased phosphorylation maintained up to 3hr of recovery in both group.

CONCLUSIONS: These results suggest that the intensitive endurance exercise positively effect on muscle protein synthesis not only in young but also in aged skeletal muscle.

153 Board #5 May 29, 9:30 AM - 11:00 AM

Aging Down-regulates Skeletal Muscle Multidrug Resistance Proteins And Increases Intramuscular Doxorubicin Accumulation

Keith Pfannenstiel, Noah M. Gibson, Colin J. Quinn, David S. Hydock, Reid Hayward. University of Northern Colorado, Greeley, CO.

(No relationships reported)

Doxorubicin (DOX) is an anthracycline currently used to treat a large number of human cancers. Multidrug resistance protein-2 and -7 (MRP-2, -7) are known to extrude DOX and may factor into the degree of intramuscular DOX accumulation.

PURPOSE: The purpose of this study was to examine age-related differences in skeletal muscle MRP expression and DOX accumulation.

METHODS: Female Sprague-Dawley rats were randomly selected to receive DOX (15 mg /kg body weight) at 4, 12, 16, 20, or 24 weeks of age. Animals were sacrificed 24 hours following injection and the soleus (SOL) and extensor digitorum longus (EDL) muscles were excised. High performance liquid chromatography was utilized to quantify DOX and Western blotting was used to analyze MRP expression.

RESULTS: No significant differences were seen in DOX accumulation in the SOL over time. DOX accumulation in the EDL was lowest at 4 weeks of age (223±139 ng DOX/g EDL) and was significantly increased (p<0.05) at 24 weeks (490±194 ng DOX/g EDL). Other significant increases (p<0.05) were observed between 12-week (225±45 ng DOX/g EDL) and 24-week as well as 16-week (257±96 ng DOX/g EDL) and 24-week animals. A significant down-regulation (p<0.05) of MRP-2 and MRP-7 expression in the EDL was seen with an increase in age. No significant down-regulation of either MRP expression was seen in the SOL.

CONCLUSIONS: These data suggest that MRP-2 and MRP-7 expression may play a role with increased intramuscular DOX accumulation of the EDL with aging.

154 Board #6 May 29, 9:30 AM - 11:00 AM

Isosorbide Dinitrate (ISDN) Supplementation Augments Aging Muscle Regeneration Following Cardiotoxin Injury

Andrew S. Layne, Kevin J. Miller, David S. Criswell, FACSM. University of Florida, Gainesville, FL.

(No relationships reported)

Aging skeletal muscle exhibits an impairment of regenerative potential, due primarily to inhibition of satellite cell activity by extrinsic factors in the aging environment. Nitric oxide is a key regulator of satellite cell activation following muscle injury. Therefore, we tested the hypothesis that augmentation of NO production by dietary supplementation of aging mice with ISDN or the NOS substrate, L-arginine, would stimulate tibialis anterior (TA) regeneration following cardiotoxin (CTX) injury.

METHODS: Four young (∼3 months) and eleven old (∼23 months) male C57BL/6J mice were divided into four groups and fed the following diets: young-control diet (YC, n=4, 10% kcal from casein), old-control diet (OC, n=4,), old-L-arginine (OA, n=4, 10% kcal from protein including 20g/kg supplemental L-arginine), and old-ISDN (OI, n=3, control diet with 4g ISDN/kg). Animals began diets 3d prior to unilateral injection of 10μM CTX in the right TA. Mice were sacrificed 10d after CTX injury and 10μm sections of injured TA were H&E stained. Muscle fiber number and cross-sectional area (CSA) were analyzed using Image J (NIH, Bethesda, MD).

RESULTS: Morphological analysis of CTX-TA confirmed complete injury in all mice (i.e. no non-regenerating fibers). Old mice exhibited a greater (-20.2%) injury-induced reduction in TA mass compared to uninjured contralateral TA vs. young mice (-12%, p<0.05). Average CSA of CTX-TA regenerating myofibers was larger in OI (1343.7±369 μm2) and tended to be larger in OC (1241.5±379 μm2) compared to YC (923.8±131 μm2, p<0.04 and 0.08, respectively). Total fiber area of CTX-TA (CSA*total number of myofibers) was lower in OC (0.1014±0.007 mm2) and OA (0.0966±0.016 mm2) compared to YC (0.1140±.004 mm2), while total fiber area in OI (0.112±0.007 mm2) did not differ from YC.

CONCLUSIONS: The total area of regenerating myofibers 10d post muscle injury is reduced in aging mice compared to young adults, despite a tendency for larger regenerating fibers in the old muscle. Dietary supplementation of aging mice with ISDN, but not L-arginine, eliminated the age-related deficit in total area of regenerating fibers suggesting the possibility of a greater functional recovery of the old muscle with ISDN treatment.

Supported by the NIH (1R03AG040400).

155 Board #7 May 29, 9:30 AM - 11:00 AM

Differential Age-Dependent Histomorphological Response Following Graded Stretch-Shortening Contraction Muscle Injury

Kayla N. Layner1, Alyssa M. Triscuit1, Robert D. Chetlin2, James Ensey1, Erik Rader1, Brent A. Baker1. 1CDC/NIOSH, Morgantown, WV. 2West Virginia University, Morgantown, WV. (Sponsor: Stephen E. Alway, FACSM)

(No relationships reported)

It is postulated that age impairs the ability of skeletal muscle to regenerate to mechanical loading due to the occurrence of increased injury. Nevertheless, the mechanism/s accounting for this disparate response with increased age is not fully understood. Experiments using stretch-shortening contractions (SSCs) provide a model to investigate skeletal muscle regeneration in response to strain injury in young and old animals.

PURPOSE: To investigate the effect of a graded, injurious SSC exposure in young and old rats.

METHODS: Left dorsiflexor muscles (LTA) of young (12 wks; n=5) and old (30 mo; n=5), male F344xBN Hybrid rats were exposed to an increasing number of 0, 30, 80, and 150 injurious SSCs in vivo. The contra-lateral right limb (RTA) served as an intra-animal control. Changes in muscle morphometry were quantified at 3 days post-injury. The left and right tibialis anterior muscles (LTA & RTA) were excised, prepared for histology, and 12 μm transverse sections were prepared and stained using H&E. Tissue sections were assessed using a standardized, quantitative stereological method.

RESULTS: No significant indices of histopathology were revealed in young RTA tissue, whereas old control tissue revealed decreased normal myofibers, increased degenerative myofibers, and increased non-cellular interstitium (indicative of edema; p<0.05). Following SSC-strain injury in young rats, data indicated a decrease in percent tissue fraction of normal myofibers (p<0.05) and an increase in non-cellular interstitium and cellular interstitium (p<0.05) as the number of SSCs were increased to 150 SSCs. However, the percent tissue fraction of degenerative myofibers was increased only following 80 SSCs (p<0.05) and plateaued thereafter in young rats. These findings were not observed in muscles from old rats, and no consistent exposure-response was noted.

CONCLUSION: These data indicate that young muscles exposed to increasing grades of injurious SSCs exhibit an exposure-response relationship supported by histopathological findings, while the histopathological findings in muscles from old rats are attenuated. Therefore, given these findings, we suggest that edema, inflammation, and degeneration are fundamentally necessary components preceding competent muscle regeneration that leads to healing.

156 Board #8 May 29, 9:30 AM - 11:00 AM

Muscle Size And Arterial Compliance After Blood Flow-restricted Low-intensity Resistance Training In Older Adults

Tomohiro Yasuda1, Kazuya Fukumura1, Taira Fukuda1, Yusuke Uchida1, Haruko Iida1, Takayuki Ohtsuka1, Yugo Chujo1, Miwa Meguro1, Yoshiaki Sato2, Toshiaki Nakajima1. 1The University of Tokyo, Tokyo, Japan. 2KAATSU International University, Rajagiriya, Sri Lanka.

(No relationships reported)

In the past decade, several studies have reported that low-intensity resistance training combined with restricted blood flow (“kaatsu”) results in significant increases in muscle size with safe arterial function in young subjects. However, the effect of kaatsu on thigh muscle size and arterial compliance in older adults remains poorly understood.

PURPOSE: To examine the effect of kaatsu on thigh muscle size and arterial compliance in older adults.

METHODS: Nineteen healthy subjects (ages 61-84 yrs) were divided randomly into a kaatsu group (KAATSU, n=9) and a non-training control group (CON, n=10). The KAATSU group performed 20% and 30%, respectively, of one-repetition maximal (1-RM) leg extension and leg press exercise (4 sets, total 75 reps. respectively), 2 days/wk for 12 weeks. The KAATSU group wore elastic cuffs (width: 50 mm) around the most proximal regional of both thighs during training, with incremental increases in external compression starting at 120 mmHg and ending at 250 mmHg. Observations before (pre) and 3-5 days after (post) the final training session were: MRI-measured muscle cross-sectional area at mid-thigh (CSA), estimated 1-RM strength, 30-sec chair stand test (CS), cardio-ankle vascular index (CAVI), and ankle brachial pressure index (ABI).

RESULTS: At baseline, there were no differences between the KAATSU and CON groups in body mass, CSA, 1-RM strength, and CAVI. After the training, CSA was increased (p<0.05) in the quadriceps (8.0%) and adductors (6.5%) but not in hamstrings (-0.2%) in the KAATSU group. In the CON group, no change was observed in each muscle CSA (-1.5%, -1.0%, and 2.1%, respectively). Leg extension and leg press 1-RM strength were increased (p<0.01) by 26.1% and 33.4% in the KAATSU group, but not in the CON group (5.2% and 1.0% respectively). CS test was increased (p<0.05) by 18.3% in the KAATSU group but not in the CON group (2.3%). In CAVI and ABI testing, there were no changes between pre- and post- results in both the KAATSU (9.1 vs. 9.0 m/sec and 1.13 vs. 1.15, respectively) and CON groups (8.7 vs. 8.5 m/sec and 1.13 vs. 1.13, respectively).

CONCLUSIONS: Our results suggested that 12 weeks of kaatsu training leads to significant increases in thigh muscle CSA as well as strength and functional ability, but there was no change in arterial compliance for older adults.

157 Board #9 May 29, 9:30 AM - 11:00 AM

Effects Of 12 Weeks Aquarobics On Atherosclerosis Factors And Anti-aging Related Substances In Elderly Women

Go-Eun Hong1, Dong-Hee Kim1, Ha-Yan Lee1, Hyun-Woong Moon1, Doo-Hong Kuk1, Woo-Suk Jung1, Seok-Hwan Kim1, Young-A Park1, 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)

Aquarobics exercise is based on aerobic training principles with water providing resistance, thus reducing the risk of injury during exercise in elderly populations. Previous studies have shown that aquarobics training improves cardiopulmonary and cardiovascular responses, however, it is not known if improvements can occur in lipid profiles or in other biomarkers related to aging.

PURPOSE: To examine the effects of aquarobics on atherosclerosis factors (TC, TG, HDL-C, LDL-C), atherogenic indexes (AI); (AI-1=(TC-HDL-C)/HDL-C; AI2=TC/HDL-C; and AI-3 = LDL-C/HDL-C) and anti-aging biomarkers (E2, DHEA-S, melatonin) in elderly women.

METHODS: Subjects were randomly assigned to either an aquarobics group (n=10) or control group (n=10, no exercise). The aquarobics group exercised for 60 minutes, 3 times per week at the intensity of 11-13 on the Borg RPE scale. Atherosclerosis factors and anti-aging biomarkers were assessed before and after 12 weeks of aquarobics. Data were analyzed by repeated measures ANOVA and statistical significance was set at α=0.05.

RESULTS: TC, TG, LDL-C were significantly decreased (p<0.05) and HDL-C significantly increased (p<0.05) in the aquarobics group following training. Additionally, AI-1 and AI-2 were significantly decreased (p<0.05) after training, while DHEA-S and melatonin were significantly increased (p<0.05). AI-3 was significantly decreased (p<0.05) in the control group.

CONCLUSIONS: Twelve weeks of aquarobics training used in this research study had a positive effect on atherosclerosis indices and anti-aging biomarkers in elderly women.

158 Board #10 May 29, 9:30 AM - 11:00 AM

Non-contractile Components In Adductors Correlate With Plasma Triglyceride In The Elderly But Not The Young

Hiroshi Akima1, Akito Yoshiko1, Maya Hioki1, Nana Kanehira2, Kiyoshi Shimaoka2, Teruhiko Koike1, Hisataka Sakakibara1, Yoshiharu Oshida1. 1Nagoya University, Nagoya, Aichi, Japan. 2Tokaigakuen University, Nagoya, Aichi, Japan. (Sponsor: Katsumi ASANO, FACSM)

(No relationships reported)

Plasma lipids concentration could associate with skeletal muscle non-contractile component (e.g. intramuscular fat and connective tissues). Age-related increase in non-contractile component is induced by sarcopenia; however, it is not well understood whether the increase in non-contractile component may account for the plasma lipids level.

PURPOSE: The purpose of this study is to assess the relationship between non-contractile components of three muscle groups in the thigh and levels of plasma triglyceride, free fatty acid (FFA), HDL-cholesterol and LDL-cholesterol in older and young individuals.

METHODS: Fifteen older (70.7 ± 3.8 years) and fifteen young (21.0 ± 0.4 years) men and women participated in the study. Axial magnetic resonance image of the right mid-thigh was taken to measure non-contractile components for the quadriceps femoris (QF), hamstrings (HM) and adductor (AD) muscle groups. MIPAV software was used to calculate non-contractile component, essentially as done previously (Akima et al. 2012). The software calculated and displayed intensity histogram for two regions of interest from muscle and subcutaneous fat, which typically contained two distinct contractile and non-contractile peaks. We determined signal intensity threshold to divide contractile and non-contractile peaks using Otsu thresholding technique. We calculated non-contractile cross-sectional area (CSA) for each muscle group. Fasted blood sample was collected to measure plasma lipids concentration.

RESULTS: In both groups, %non-contractile CSA of HM was significantly higher than QF and AD. %Non-contractile CSA of HM in the older was significantly higher than that of the young, but no significant difference in QF and AD between the older and young. There was a significant correlation between plasma triglyceride concentration and %non-contractile CSA in AD (r=0.531, p<0.05) in the older, but no significant correlation was found in the young. No significant correlation was found between non-contractile component and the other lipids in both groups.

CONCLUSIONS: These results suggest that a large amount of non-contractile content was stored in HM in the older and young, but age-related non-contractile contents in AD have relevancy to plasma triglyceride level.

Supported by KAKENHI grant #23650432.

159 Board #11 May 29, 9:30 AM - 11:00 AM

Comparisons Of Non-contractile Tissue In Individual Muscles Of Quadriceps Femoris Between Young And Old Subjects

Akito Yoshiko1, Maya Hioki1, Nana Kanehira2, Kiyoshi Shimaoka2, Teruhiko Koike1, Hisataka Sakakibara1, Yoshiharu Oshida1, Hiroshi Akima1. 1Nagoya University, Nagoya, Japan. 2Tokai gakuen University, Nagoya, Japan. (Sponsor: Katsumi Asano, FACSM)

(No relationships reported)

It would be necessary to take into account the non-contractile components, such as fat and/or connective tissue, was infiltrated into a given muscle, when we evaluate the size of skeletal muscle in humans. The proportion of non-contractile cross-sectional area (CSA) within muscle is recognized to increase with aging. However, it is not clear whether there are specific changes in %non-contractile CSA, i.e. the relative value of non-contractile CSA to conventional muscle CSA, among individual muscles of quadriceps femoris (QF).

PURPOSE: The purpose of this study is to examine %non-contractile CSA of individual muscles in QF, and compare those between young and old subjects.

METHODS: Fifteen young (8 males and 7 females, 21.0 ± 0.4 years) and fifteen old (7 males and 8 females, 70.7 ± 3.8 years) subjects were taken axial T1-weighted images at the mid-thigh using magnetic resonance imaging. MIPAV software was used to calculate non-contractile components, essentially as done previously (Akima et al. 2012). The software calculated and displayed intensity histogram for two regions of interest from muscle and subcutaneous fat, which typically contained two distinct contractile and non-contractile peaks. We determined signal intensity threshold to divide contractile and non-contractile peaks using Otsu thresholding technique. We calculated %non-contractile CSA for each muscle.

RESULTS: %Non-contractile CSA of vastus lateralis (VL) and vastus intermedius (VI) in old subjects were significantly higher than those in young (VL, 6.4 ± 3.2% [old] vs. 2.8 ± 1.2% [young]; VI, 4.5 ± 3.4% [old] vs. 1.1 ± 0.5% [young]; p < 0.01), but there were no significant difference in rectus femoris (RF) and vastus medialis (VM). There were no significant correlation coefficients of %non-contractile CSA among individual muscles in the young; however, in the old, there were significant correlation coefficients between VL and VM, RF and VM, RF and VI, and VM and VI (r=0.52 to 0.82, p < 0.05).

CONCLUSIONS: These results suggested that, as we expected, old individuals have relatively higher fat and/or connective tissue was infiltrated into muscles in the QF, and that this age-related muscle changes could occur simultaneously among the four individual muscles of QF.

160 Board #12 May 29, 9:30 AM - 11:00 AM

Mechanical Determinants Of Muscle Power In Women And Men Aged 18-81 Years: Influence Of Age And Gender

Cecilia E. Edwén1, Jonas B. Thorlund2, S. Peter Magnusson3, Frode Slinde4, Ulla Svantesson1, Lena Hulthén4, Per Aagaard2. 1Institute of Neurosciences and Physiology, University of Gothenburg, Gothenburg, Sweden. 2Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark. 3Institute of Sports Medicine, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark. 4Department of Internal Medicine & Clinical Nutrition, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.

(No relationships reported)

Muscle power is an important factor for activities of daily living and for avoiding falls. This study explored the age-related deterioration in stretch-shortening cycle (SSC) muscle power and concurrent force-velocity properties in healthy women and men across the adult lifespan.

PURPOSE: To determine the influence of aging and gender in relation to maximal SSC muscle power produced during coupled eccentric-concentric muscle contraction in 315 women (n=180) and men (n=127) aged 18-81 years.

METHODS: Maximal counter-movement jumps were performed on a force plate (1000 Hz) and instantaneous vertical power (P) production was calculated throughout the entire movement.

RESULTS: Maximal SSC leg extension power (W/kg) was greater in men than women across the age span (p<0.001), however this gender difference was progressively reduced with increasing age, since P declined with aging at a ∼50% faster rate in men than women (0.44 vs. 0.29 W/kg per year) (p<0.001). Velocity at peak power (VPpeak) was greater in men than women (p <0.001) but declined at a greater rate in men than women (-0.02 vs. -0.01 m/s per year) (p=0.002). Vertical ground reaction force at peak power (FPpeak) was higher in men than women in younger adults only (18-34 yrs) (p<0.001) and the age related decline was steeper in men than women (0.07 vs. 0.04 N/kg per year)(p<0.001). Rate of force development (RFD) obtained during the CMJ declined with aging at a similar rate in women and men (-0.79 and -0.88 Nm/s/kg per year), but was higher in middle aged and old women (p<0.05) compared to age-matched men.

CONCLUSION: Maximal stretch-shortening cycle leg extension power is greater in men than women throughout the adult lifespan, but declines at a greater rate in men, such that maximal SSC power production converge between women and men when approaching old age.

161 Board #13 May 29, 9:30 AM - 11:00 AM

Effect of Maturation Scale on Comparative Knee Joint Morphologies

Steven Davidson, Jessica M. Deneweth, Grant C. Goulet, Scott McLean. Universtiy of Michigan, Ann Arbor, MI.

(No relationships reported)

The impact of maturation on lower limb joint injury risk continues to gain substantial research momentum. Obtaining data that is accurate and reliable however, requires a successful method of maturation delineation.

PURPOSE: This study compared the sensitivity of explicit knee joint morphologies to maturation state via two known maturation scales with differing criteria.

METHODS: Knee morphologic indices linked to joint injury were quantified in 13 female subjects (ages 9-16 yrs) via segmentation and measurement of a series of high-resolution 2-D Magnetic Resonance (MR) images (McLean 2010). Specifically lateral tibial slope (LTS) angle, and normalized (body weight) anterior cruciate ligament (ACL) and intercondylar notch (ICN) volume. Subjects were stratified into early, mid and later pubertal groups via two previously validated methods; the Pubertal Maturation Observation Scale (PMOS) (Quatman et al., 2006) and the Skeletal Maturation Scale (SMS) (O’Connor et al., 2012). The main effect of maturation on each measure was examined via two-tailed t-tests and compared between scales. An alpha level of p=0.05 denoted statistical significance.

RESULTS: Using the SMS, 3 (avg=10 yrs), 5(avg=14 yrs), 5(avg=14 yrs) subjects were stratified into respective early, mid, and late maturation groups, with significant differences in ACL volumes and LTS angle between early/mid groups and in all measures between early/late groups. Using the PMOS 5 (avg=11.4 yrs), 0, and 8 (avg=15 yrs) subjects were stratified into respective early, mid, and late maturation groups with a significant difference in ACL volume between early/late groups.

CONCLUSIONS: Current results demonstrate the observed sensitivity of key knee morphologies to maturation status is directly dependent on the overarching maturation stratification method. With such morphologies considered key risk factors for knee injury, an inaccurate delineation of maturation state may adversely impact future risk screening and prevention methods. In particular, determination of optimal timing for implementing these methods may be compromised. Maturation stratification via tibial and femoral epiphyseal plate data, as with the SMS approach, appears to provide the most objective means of defining maturation state as this research theme continues to move forward.

162 Board #14 May 29, 9:30 AM - 11:00 AM

Maturational Changes in the Rate of Torque Development

Izabella Ludwa1, Glenn Jenkins1, Steve Hansen2, Raffy Dotan1, Panagiota Klentrou1, Bareket Falk1. 1Brock University, St. Catharines, ON, Canada. 2Nipissing University, North Bay, ON, Canada. (Sponsor: Dr. David Gabriel, FACSM)

(No relationships reported)

Children are characterized by lower muscle strength compared with adults, even after correcting for size differences. Their maximal rate of force development has also been demonstrated to be lower than adults’.

PURPOSE: To investigate maturational changes in the rate of force development and the factors that may affect these changes.

METHODS: Participants were 21 pre-pubertal (PPm; 9.9±1.3yrs), 17 late-pubertal (LPm; 13.6±1.5yrs), and 14 adult (Am; 21.8±1.7yrs) males; as well as 35 pre-pubertal (PPf; 9.8±1.1yrs), 13 late-pubertal (LPf; 13.5±1.8yrs), and 15 adult (AF; 21.4±2.1yrs) females. Knee extension peak torque (PT) and rate of torque development (RTD) were determined isometrically as well as isokinetically at 60 and 240°/s (Biodex System 3). Quadriceps muscle cross-sectional area (CSA) was estimated ultrasonically (GE Vingmed, B-Mode, 5Hz). Electromyography (EMG) was used to determine electro-mechanical delay (EMD) and the initial rate of EMG rise (Q30).

RESULTS: PT and RTD were significantly higher in males and increased significantly with maturity at all velocities, even after correction for muscle CSA. However, there were no significant differences in RTD between LP and adults of both sexes. The male isometric RTD was 60.1±19.9, 89.6±32.7, and 87.4±29.5 in PPm, LPm and Am, respectively. A similar pattern was observed for females, as well as in the isokinetic contractions. EMD was similar in males and females and decreased with maturity. The male isometric EMD was 72.6±18.9, 66.8±11.5, and 62.4±21.7ms in PPm, LPm and Am, respectively. A similar pattern was observed for females. EMD was negatively correlated with RTD (r=-0.26 to -0.31). On the other hand, no group differences were observed in the initial rate of EMG rise and it was not correlated with RTD.

CONCLUSIONS: Since EMD partly reflects musculo-tendinous stiffness, the results suggest that maturity-related differences in RTD are partly explained by age-related changes in musculo-tendinous stiffness, but not by changes in the rate of EMG rise. Further research is needed to examine maturity-related changes in neuromuscular factors which may affect muscle function.

Funded by the Canadian Institute for Health Research

163 Board #15 May 29, 9:30 AM - 11:00 AM

Sex-specific Relationships Between Physical Activity, Maturity, Calcium, And Bone, Muscle And Fat In Peri-pubertal Children

Rossana C. Nogueira, Benjamin K. Weeks, Belinda R. Beck, FACSM. Griffith University, Gold Coast, Australia.

(No relationships reported)

Relationships between physical activity (PA), maturity, diet and musculoskeletal status have been observed during childhood, but sex-specific differences are poorly understood.

PURPOSE: To examine the sex-specific relationships between PA, biological maturity and calcium consumption and indices of musculoskeletal health in a cohort of healthy pre- and peri-pubertal girls and boys.

METHODS: 330 eligible children volunteered to participate. Maturity was defined as years from age of peak high velocity (YAPHV); determined from height, weight and sitting height. Historical PA was derived from the Bone-specific Physical Activity Questionnaire (BPAQ). Calcium consumption was determined from the Australian Children and Adolescent Eating Survey (ACAES). Markers of musculoskeletal health, including calcaneal broadband ultrasound attenuation (BUA) (Achilles, GE), whole body (WB), lumbar spine (LS), femoral neck (FN) and trochanteric (TR) bone mineral density (BMD), lean mass (LM) and percent fat (%fat) (DXA, XR-800, Norland), tibial volumetric density at the 4% site and cortical thickness at the 38% site (pQCT, XCT3000, Stratec) were measured.

RESULTS: There were no sex differences in any variable except YAPHV, which was greater in boys (p< 0.001), and BPAQ score which was greater in girls (p<0.001). YAPHV predicted variance in WB BMD (R2=0.61; p<0.001), LS BMD (R2=0.21; p=0.01), %fat (R2=0.23; p=0.01) and LM (R2=0.75; p<0.001) for boys. YAPHV predicted roughly the same degree of variance in WB BMD (R2=0.59; p=0.001), LS BMD (R2= 0.30; p<0.05), and a slightly greater amount of TR BMD (R2=0.54, p=0.002), and LM (R2=0.84; p<0.001), for girls; also explaining variance in FN BMD (R2=0.50; p=0.003) and BUA (R2=0.29; p<0.001). Tibial cortical thickness was related to YAPHV for girls (r=0.52, p<0.03) and boys (r=0.65, p<0.0001). Tibial volumetric density at the 4% site was related to YAPHV only for girls (r=0.59, p=0.01). Neither calcium nor PA explained variance in any musculoskeletal variable for either sex in regression models.

CONCLUSIONS: Maturity, defined as years from age of peak height velocity, largely accounts for variance in bone, fat and muscle status in both male and female pre- and peri-pubertal children, while PA and calcium are less influential. YAPHV predicted FN, TR BMD and calcaneal BUA in girls only.

164 Board #16 May 29, 9:30 AM - 11:00 AM

Acute Effects Of Stretching On Passive Stiffness And Maximum Range Of Motion: Influence Of Aging

Eric D. Ryan1, Trent J. Herda2, Pablo B. Costa3, Ashley A. Herda4, Joel T. Cramer, FACSM5. 1University of North Carolina at Chapel Hill, Chapel Hill, NC. 2University of Kansas, Lawrence, KS. 3California State University - San Bernardino, San Bernardino, CA. 4University of Kansas School of Medicine, Prairie Village, KS. 5University of Nebraska - Lincoln, Lincoln, NE.

(No relationships reported)

Passive stretching is often performed with the intent to increase maximum range of motion (MROM) and reduce passive stiffness. Due to the number of aging-related changes in neuromuscular function, older adults may respond differently to an acute bout of passive stretching.

PURPOSE:To examine the influence of aging on the acute stretching-induced changes in MROM and passive stiffness.

METHODS:Twenty-one healthy young (22.4 ± 1.9 yrs) and 19 old (69.8 ± 5.5 yrs) men performed MROM assessments of the plantar flexor muscles on a modified, custom-built load-cell apparatus connected to a calibrated Biodex System 3 dynamometer prior to and following nine 135-s passive stretches. Position (°) and torque (Nm) values were sampled from the dynamometer, while EMG amplitude values (μV) were recorded from the soleus and medial gastrocnemius muscles. Passive stiffness values (Nm°-1) were calculated from the gravity corrected angle-torque curve using a fourth-order polynomial function at every other degree (θ) for the final common 5° range of motion (θ1, θ3, and θ5). MROM was calculated from the highest average range of motion values (40-ms epoch). A two- and three-way mixed factorial ANOVA were used to analyze passive stiffness and MROM, respectively. ANCOVA was used to analyze the magnitude of change when baseline values were different.

RESULTS:Pre-stretching MROM was greater in the young than the old (P=0.024), however, there were no differences in MROM between age groups after stretching (P=0.229). ANCOVA demonstrated that the corrected post-stretching MROM values were greater for the old than the young (P=0.028). Passive stiffness values were greater for the young than the old at all time points, increased across joint angles (θ1<θ3<θ5) and decreased from pre- to post-stretching for both the young and the old (P<0.001). ANCOVA showed that the corrected post-stretching passive stiffness values were similar between the young and the old (P=0.166 - 0.621) at each joint angle.

CONCLUSIONS:The older adults achieved greater increases in MROM (young=5% vs. old=8%) following an acute bout of passive stretching, despite similar decreases in passive stiffness. This age-related increase in MROM may have been due to impairments in stretch reflex feedback mechanisms.

© 2013 American College of Sports Medicine