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A-36 Free Communication/Poster - Cardiovascular I

Medicine & Science in Sports & Exercise: May 2013 - Volume 45 - Issue 5S - p 30–40
doi: 10.1249/01.mss.0000433611.13309.0d

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

Room: Hall C

185 Board #37 May 29, 9:30 AM - 11:00 AM

Sex Differences In The Hemodynamic Response To Reductions In Radial Artery Transmural Pressure With Arm Elevation

Ari G. Kasprowicz1, Brendan J. Tarzia1, Justin E. Davies2, Darren P. Casey3, Kevin S. Heffernan1. 1Syracuse University, Syracuse, NY. 2International Center for Circulatory Health, London, United Kingdom. 3Mayo Clinic, Rochester, MN. (Sponsor: Bo Fernhall, FACSM)

(No relationships reported)

The force of gravity affects blood pressure (BP) by influencing intravascular pressure gradients. Men and women regulate BP differently in response to perturbations that alter pressure gradients such as orthostatic challenge.

PURPOSE: We examined the peripheral hemodynamic response to arm elevation as a means of studying potential sex differences in gravity-induced changes in BP.

METHODS: Radial artery pressure waveforms were obtained using applanation tonometry in 20 men (age 27±2 yrs, BMI 25±1 kg/m2) and 20 women (age 27±2 yrs, BMI 23±1 kg/m2). Arm position was maintained at either heart level or supported 14 cm above heart level in a randomized fashion. Amplitude of the late systolic shoulder (P2) of the radial pressure waveform was used as a measure of pressure attributable to wave reflections. A reservoir-wave separation technique was used to obtain the arterial reservoir pressure (pressure generated by arterial capacitance discharge).

RESULTS: Women showed a significant reduction in radial diastolic blood pressure (DBP) (69±2 to 66±1 mmHg; p<0.05) and reservoir pressure (16.8±1.2 to 14.2±1.2 mmHg; p<0.05), with no change in P2 (26.9±1.3 to 26±1.4 mmHg; p>0.05) during arm elevation. Conversely, men showed no change in radial DBP (70±2 to 69±1 mmHg, p>0.05) while showing a significant increase in reservoir pressure (11.9±1.3 to 14.5±1.2 mmHg; p<0.05) and P2 (25.3±1.3 to 28.7±1.4 mmHg, p<0.05) during arm elevation.

CONCLUSION: Gender differences exist in hemodynamic regulation in response to gravity-induced changes in regional BP. In response to arm elevation, men maintain DBP possibly via increased pressure from wave reflections and reservoir pressure. Women experience a drop in regional DBP and this may be due to reductions in reservoir pressure coupled with inability to increase pressure from wave reflections.

186 Board #38 May 29, 9:30 AM - 11:00 AM

Resting Transthoracic 3d Echocardiography Provides Additional Information On The Rv Chamber Morphology Of Young Trained Athletes

Alessio De Luca, Laura Stefani, Giorgio Galanti. Sports Medicine Centre, Florence, Italy.

(No relationships reported)

PURPOSE: Regular training induces a global heart remodeling involving the right ventricle (RV). Few studies have assessed the normal geometry and function of this chamber particularly in healthy young athletes where the onset of the athletes’ heart is not yet completely recognizable. Despite the current use 2D RVAC, a special evaluation by the 3D echo reconstruction is not yet considered. The study aims to compare the two methods in this aspect .

METHODS: Basal RV chamber function were assessed in 25 young trained athletes (20 soccers and 5 basketball) aged 20 ±3 yrs and 20 sedentary controls by 2D-AC and 3D-RV methods (TomTec), measuring RV diastolic (RVDV) and systolic (RVSV) volumes or EF.

RESULTS: 3D - RV volumes were slightly higher in athletes (RVDV: 106.14 ± 30.3 ml; RVSV: 50.74 ± 15.25 ml) than in sedentary (88.0 ± 41.36 ml; 40.67 ± 23.96 ml). On the contrary, the 2D volumes were lower in athletes, even if not significantly, (RVDV: 43.40 ± 13.11 ml; RVSV: 21.13 ± 6.5 ml) than in sedentary (45.33 ± 14.05 ml; 22.0 ± 7.8 ml). EF values, calculated by both methods, were slightly but not significantly lower in athletes (3D-RV: 52.10 ± 6.4%; 2D-AC: 50.865 ± 6.5%) than in sedentary (55.61 ± 7.4%; 52.0 ± 4.0%). Significant differences were conversely found comparing 3D-RV and 2D-AC volumes within each group (RVDV: p=.001 for athletes and p<.001 for sedentary, RVSV: p<.04 for athletes and p<.001 for sedentary), but without significant EF difference.

CONCLUSIONS: The 2D and 3D methods cannot be considered completely coincident for the assessment of the RV in young “athlete’s heart”. The 3D assessment of young athletes RV chamber adds more accurate information on the morphological aspects suggestive for a better analysis on the early remodeling than 2D.

187 Board #39 May 29, 9:30 AM - 11:00 AM

Validation of Oscillometric Pulse Wave Analysis Measurements in Children

Lee Stoner1, Nicole Westrupp1, Danielle M. Lambrick1, Melanie S. Poudevigne, FACSM2, Joanne M. Young3, James A. Faulkner1. 1Massey University, Wellington, New Zealand. 2Clayton State University, Morrow, GA. 3Lipid and Diabetes Research Group, Christchurch, New Zealand.

(No relationships reported)

Pulse wave analysis (PWA) has emerged as a non-invasive, valid, reliable and widely used technique to investigate mechanical properties of the arterial tree, including central blood pressures and arterial stiffness. The “gold standard” technique is tonometry, but this technique can be challenging, especially when used on children. Oscillometric devices are user-friendly, practical for use in epidemiological studies, and suitable for use on a range of populations.

PURPOSE: To validate oscillometric PWA for use in children.

METHODS: Fifty four healthy children were recruited for participation. Demographic and anthropometric data were collected at baseline. Central blood pressures and peripheral augmentation index (pAIx) were measured objectively using the oscillometric (PulseCor) and tonometric (SphygmaCor) monitors. The tonometric device also measured central augmentation index (cAIx). All measurements were made during the same visit under standardized conditions between the hours of 8am and 10am in the fasted state.

RESULTS: Successful oscillometric PWA measurements were taken on all participants. Tonometric PWA measurements were successfully taken on 53 of the 54 children. Comparisons were made on 53 children (9.8+1.0 yrs, 57% male). A very strong relationship was found for central systolic (SBP; r = 0.95, p = <0.001), central diastolic (r = 0.99, p = <0.001) and central mean (r = 0.99, p = <0.001) blood pressures. However, there was a bias towards greater SBPs with the oscillometric monitor (mean difference: 6.5 mmHg). A strong relationship was found for pAIx (r = 0.68, p = <0.001), and for pAIx measured with the oscillometric device and cAIx measured with the tonometric device (r = 0.55, p = <0.001).

CONCLUSION: Findings from this study suggest that oscillometric PWA measurements may be suitable for use on paediatric populations. Further studies are required to compare changes in pAIx and cAIx in response to diseased states and lifestyle interventions.

188 Board #40 May 29, 9:30 AM - 11:00 AM

Altered Autonomic Response to Upright Tilt in Individuals With Down Syndrome

Kanokwan Bunsawat1, Stella Goulopoulou2, Scott Collier, FACSM3, Arturo Figueroa, FACSM4, Kenneth Pitetti, FACSM5, Bo Fernhall, FACSM1, Tracy Baynard1. 1University of Illinois, Chicago, IL. 2Georgia Health Sciences University, Augusta, GA. 3Appalachian State University, Boone, NC. 4Florida State University, Tallahassee, FL. 5Wichita State University, Wichita, KS. (Sponsor: Bo Fernhall, FACSM)

(No relationships reported)

Previous research has reported altered autonomic function in individuals with Down syndrome (DS) at rest and in response to certain stimuli (i.e. isometric handgrip, aerobic exercise, and even tilt table testing). Yet, these observations have been made using group means in these previous studies. It is unknown if a subset of individuals with DS that have similar heart rate responses to a task would have similar responses in heart rate variability (HRV).

PURPOSE: To compare autonomic function between individuals with and without DS, via HRV analyses, using upright tilt and matching subjects on change in HR to tilt.

METHODS: Individuals with (25 ± 7 yrs; 30.4 ± 7.3 kg/m2) and without DS (27 ± 7 yrs; 24.7 ± 4.1 kg/m2) (n=15/group) were matched on their HR response to a 5 min head-up tilt at 80°. HRV was assessed in both the frequency (low frequency (LF), high frequency (HF), and LF/HF ratio) and time domains (Root mean square of successive differences (RMSSD)). A modified CM5 lead was used with data collected at 1000 Hz.

RESULTS: Raw HRV data are presented below. As expected, tilt effects were observed for HR, HF, LF/HF ratio, and RMSSD in both groups, with no group differences (*p<0.05). However, individuals with DS exhibited a reduction in LF with no change in the control group (†p<0.05).

CONCLUSION: Parasympathetic modulation appeared to be similar between individuals with DS and non-DS in response to orthostatic stress. LF, which contains both sympathetic and parasympathetic influences, responded quite differently to tilt in individuals with DS, suggesting possible autonomic dysfunction despite their normal HR response.

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189 Board #41 May 29, 9:30 AM - 11:00 AM

Impact of Obesity and Down Syndrome on Maximal Heart Rate and Work Capacity in Youth and Adults with Intellectual Disabilities

Sang Ouk T. Wee1, Ken Pitetti, FACSM2, Tracy Baynard1, Bo Fernhall, FACSM1, Miriam Elisa Guerra Balic3. 1University of Illinois at Chicago, chicago, IL. 2Wichita State University, Wichita, KS. 3Ramon Llull University, Barcelona, Spain.

(No relationships reported)

PURPOSE: Obesity in Down syndrome (DS) is a very common

health condition. Individuals with DS show low cardiovascular function such as

low peak heart rate (HR peak) and peak oxygen consumption (VO2peak). It is

unknown if obesity affects HR peak and VO2peak in this population. PURPThe purpose of this study was to investigate the effects of DS, Intellectual disability (ID) and obesity on determinants of exercise performance, such as peak heart rate (HR peak) and peak oxygen consumption (VO2peak) in children and adults.

METHODS: 425 adults, 100 with ID, 77 with DS, 248 controls,

as well as 165 children, 83 with DS, and 82 with ID participated in this study. Each participant performed a maximal walking treadmill test, with VO2 and HR measurements. Analysis of variance (ANOVA) and Analysis of covariance (ANCOVA) were used to analyze the data.

RESULTS: (See table) Obese adults exhibited significantly lower VO2peak and HRpeak compared to their nonobese peers in all groups (p<.05). Conversely, in children with DS, obesity had no effect on HRpeak and less impact on VO2peak than in children with ID. Obese children with ID had lower HRpeak and VO2peak than their nonobese peers (p<.05).

CONCLUSIONS: The results suggest that obesity impacts HRpeak and VO2peak differently in children with DS than in children with ID or in adults with or without DS. This may imply that obesity is associated with autonomic dysfunction in children with ID and in adults regardless of group, but not in children with DS.

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190 Board #42 May 29, 9:30 AM - 11:00 AM

Vascular Function in Parkinson’s Disease Patients

Brandon S. Pollock1, Keith J. Burns1, Angela L. Ridgel1, John McDaniel2. 1Kent State University, Kent, OH. 2Cleveland Veterans Affairs Medical Center, Cleveland, OH. (Sponsor: Ellen Glickman, FACSM)

(No relationships reported)

BACKGROUND: It is believed that oxidative stress (an imbalance between free radicals and antioxidant defense) contributes to the cascade leading to dopamine cell degeneration in Parkinson’s disease. Additionally, oxidative stress results in decreased nitric oxide bioavailability, inflammation and ultimately vascular dysfunction. Thus it is possible that the exercise intolerance associated with Parkinson’s disease partially results from oxidative stress induced vascular dysfunction and subsequent poor blood flow to the exercising muscles.

PURPOSE: The purpose of this research is to use the standard flow mediated dilation (FMD) protocol to determine if endothelial dysfunction is present in individuals diagnosed with Parkinson’s disease.

METHODS: Eight individuals diagnosed with Parkinson’s disease (68.8 ± 4.5 years) and five healthy controls (74.8 ± 5.5 years) were recruited for this investigation. A Doppler ultrasound system was used to measure participant’s brachial artery diameter and blood velocity at baseline and for the first 2 minutes immediately following 5 minutes of forearm blood flow occlusion. %FMD was calculated as: %FMD = (peak diameter - baseline diameter) / baseline diameter. %FMD relative to shear was also determined. Independent samples t-tests were used to determine differences in %FMD and %FMD / Shear between groups.

RESULTS: Independent samples t-test revealed a significant difference (p = .047) in %FMD between the Parkinson’s group (6.54 ± 4.13%) and control group (12.13 ± 4.81%). Although shear was not different (p = 0.9), when %FMD was expressed relative to shear, there was no longer a significant difference (p = .220) observed between the control group (.0003 ± .00015) and Parkinson’s group (.0002 ± .00019).

CONCLUSIONS: Although PD subjects exhibited a reduced %FMD compared to healthy controls, there was no difference when expressed relative the stimulus for dilation, shear. Thus, these data indicate that endothelial dysfunction may not be present in PD patients beyond what is expected with normal aging.

191 Board #43 May 29, 9:30 AM - 11:00 AM

A Study of Peripheral Autonomic Features of Younger Populations with Family History of Hypertension

Shih-wei Chen1, Philip Chen2, Lan-Yuen Guo1. 1Kaohsiung Medical University, Kaohsiung, Taiwan. 2University of California, Berkeley, CA.

(No relationships reported)

Familial history of hypertension (FHH) is a major risk factor in the development of hypertension. Only few studies were focused on the early detection in physiological change among the young population with FHH.

PURPOSE: In our study, we compared cardiac autonomic features and microvascular blood flowof young normotensives with FHH (NT+) and normotensives without FHH (NT-) for examining the possible early sign.

METHODS: Sixteen normotensives assigned to two groups (age 18∼30 years, systolic blood pressure (SBP) ≤ 140 mmHg and diastolic blood pressure (DBP) ≤ 90 mmHg) according to the presence (NT+, N = 8) or absence (NT-, N = 8) of FHH. Autonomic nervous system and microvascular blood flow were measured by using heart rate variability (HRV) analysis and laser-Doppler flowmetry (LDF). Ten minutes readings of HRV and LDF data was analyzed for their fourier power spectra. We measured the high frequency (HF), which represents parasympathetic nervous activity, the low frequency/high frequency ratio (LF/HF), which represents sympathetic nervous activity. Laser Doppler signals were recorded in blood perfusion units (BPU).

RESULTS: NT+ group had a higher LF/HF ratio (NT-: 0.94, NT+: 1.36, p>0.05) and a lower HF (NT-: 46.49 n.u., NT+: 43.65 n.u., p>0.05) than NT- group. We also found that the lower microvascular blood flow values (NT-: 776.09 BPU, NT+: 718.70 BPU, p>0.05) in NT+ group and contained a larger proportion of vascular myogenic activity (NT-: 34.34%, NT+: 40.40%, p>0.05).

CONCLUSION: The findings of this study suggested that cardiac autonomic and microvascular features may serve as risk factors for hypertension development in young population with FHH.

192 Board #44 May 29, 9:30 AM - 11:00 AM

Lactate Concentration Response to Knee Extension Exercise with Various Initial Restrictive Pressures in Females

Joe-Angel Lopez, Guillermo Perez, Murat Karabulut. University of Texas at Brownsville, Brownsville, TX.

(No relationships reported)

Literature remains lacking in regards to the role that initial restrictive pressure (IRP) coupled with resistance training as it pertains to the production and accumulation of metabolic byproducts such as lactate, more specifically in women.

PURPOSE:The present study investigates the importance of the IRP as a variable on lactate concentrations during knee extension exercise in combination with blood flow restriction in female subjects.

METHODS:Thirteen female volunteers (age 21± 1.35) served as the test sample for this study. Initial health screening, PAR-Q, signing of the informed consent, procedural and dynamometer setting familiarization were completed on the first meeting. Prior to exercise, the participants’ maximal voluntary contraction (MVC) torque of right leg extensors was measured using an isokinetic dynamometer. Participants performed knee extension exercise with IRP set randomly at either 40-45 mmHg or 60-65 mmHg on two subsequent visits separated by a minimum of 48 hours. On each visit, participants performed 4 sets (1×30 reps and 3×15 reps) of dynamic knee extension exercises with the load set at 20% of their respective MVC. The load lifted for both visits was the same and determined using pre-MVC. A lactate analyzer was employed to measure lactate concentration within blood sample from finger pricks. Participants washed their hands before testing started and isopropyl alcohol wipes were used to clean the puncture site before the collection of blood. Levels of lactate concentration were measured prior to exercise, between the second and third sets, and at immediately post exercise.

RESULTS:A significant main effects for time (p0.05) between the conditions (40-45 mmHg vs. 60-65 mmHg) over the course of dynamic knee extension exercise.

CONCLUSIONS:Given that females may have more adipose tissue accumulated around their hip and thighs, magnitude of the effect of IRPs may vary within and across genders, resulting in changes in the type of muscle fibers (type I vs. type IIx) recruited, the total number of muscle fibers recruited, and the level of fatigue. More research is required to determine the impact of various IRPs on the level of byproduct production and accumulation.

193 Board #45 May 29, 9:30 AM - 11:00 AM

Is There An Association Between Different Morphological Bav Patterns And LV Dimensions In Athletes From Different Kinds Of Sports?

Laura Stefani, Gabriele Innocenti, Roberto Mercuri, Giorgio Galanti. Sports Medicine Centre, Florence, Italy.

(No relationships reported)

PURPOSE: BAV is a congenital cardiac disease, represented in two different morphologies “typical (raphe) or atypical(no- raphe) “.In athletes, BAV is associated to a progressive enlargement of the LV chamber. The exact prevalence of the two BAV patterns in athletes and the possible association with the enhancement of the LV in them, is not yet investigated . The study aims to verify in a large group of athletes from different kinds of sports, the prevalence of the two mainBAV morphologies eventually associated to a diverse the LV dimensions.

METHODS: from 2000 to 2011, a group of 292 BAV subjects, ( athletes , sedentary and ex- athletes), were investigated. They were submitted to an 2D echo exam ( MayLab 50 -ESAOTE) to classify the BAV morphology and to measure the LV sisto-diastolic parameters (LV diameters , wall thickness and CMI). T Student Test and ANOVA test were used to compare the data.

RESULTS: The typical BAV was more represented in all the groups ( 68%,67%,63%) than atypical. Within the typical BAV pattern the form due to the fusion of the right cusp with the left one, was more common ( 70%,73%,62%) in all the groups . In athletes only,typical BAV was found in 51% of soccer players , in 10% of basketball players, in 8% of cyclists, 6% swimmers, and 15% rugby players. All the echo parameters didn’t show any statistical differences with respect of the different morphological BAV patterns and also to the different kind of sports.

Conclusions: The results are in agreement with the current literature and confirm the prevalence of BAV in athletes is similar to the general population. Despite the LV diameters found were at the upper limits of the normal range , however there are no differences for this aspect among the diverse BAV patterns associated.

194 Board #46 May 29, 9:30 AM - 11:00 AM

Maternal Exercise During Pregnancy Does Not Influence Glucose Clearance or Vascular Function in Adult Offspring

Nicole Blaize, Shawn S. Donkin, Ryan Cabot, Sean C. Newcomer. Purdue University, West Lafayette, IN.

(No relationships reported)

Negative behaviors during pregnancy, such as poor nutrition or smoking, have been shown to have adverse health outcomes in the offspring later in life. While considerable research effort has been expended in understanding this paradigm, little attention has been focused on positive behaviors during pregnancy and the impact on offspring health outcomes.

PURPOSE: To determine the effects of exercise during pregnancy on glucose disposal and vascular function in the offspring in a rodent model of fetal programming.

METHODS: Female Sprague Dawley rats were divided into exercise (EX: N =9) or sedentary (SED: N =10) groups with the exercising group having voluntary access to a running wheel throughout gestation. Litter characteristics (weight and size) were taken one day after birth. Two male and two female offspring from each dam were weaned and assigned to a normal (N) or high-fat (HF) diet. Glucose tolerance tests were performed on the offspring at 3.5 months of age. Offspring were euthanized at 4 months of age; the abdominal aorta was harvested and used for in vitro vascular function experiments. Endothelium-dependent and -independent dose dependent vasorelaxation was assessed using increasing doses of acetylcholine (ACH; 10-10-10-4M) and sodium nitroprusside (SNP; 10-10-10-4M), respectively.

RESULTS: There were no significant differences in weight gain between the exercise and sedentary dams throughout gestation (EX: 136.29 ± 18.1 g; SED: 161.53 ± 18.63 g). The EX dams ran an average of 2.32 ± 0.38 km/day. There were no significant differences in litter size (EX: 13.78 ± .40 pups; SED: 13.67 ± 0.82 pups; p = 0.848) or weight between the exercise and sedentary groups. There were no significant differences in overall glucose disposal (AUC*T mg/dL*120 min) between the offspring from sedentary (Male HF: 21,776 ± 2,229; Female HF: 29,723± 2,480; Male N: 24,364± 2,617; Female N: 24,872± 2,474) or exercise (Male HF: 26,085± 2,560; Female HF: 28,171± 719; Male N: 21,183± 2,209; Female N: 25,424± 2,155) dams. There were no significant differences in vasorelaxation response to ACH or SNP between the offspring from sedentary or exercise dams.

CONCLUSION: Maternal exercise during pregnancy does not significantly alter offspring litter characteristics at birth or glucose disposal and vascular function at 4 months of age.

195 Board #47 May 29, 9:30 AM - 11:00 AM

Day-to-day Reliability Of Flow-mediated Dilation Measures In The Popliteal Artery

Kaitlin M. McLay, Juan M. Murias, Josh P. Nederveen, Donald H. Paterson, FACSM. University of Western Ontario, London, ON, Canada.

(No relationships reported)

Flow mediated dilation (FMD) is a technique commonly used to noninvasively assess vascular endothelial function. Reliability of this technique has important implications for its application to both clinical and research settings.

PURPOSE: To determine the stability (day-to-day) reliability of FMD measures in the popliteal artery.

METHODS: A series of five FMD tests were performed over 5 consecutive days on ten healthy young males (27±6 yrs) to assess reliability. Ultrasound derived artery diameter of the popliteal was measured at baseline and for 5 minutes following a 5 minute period of distal cuff occlusion. FMD responses were evaluated as the greatest percent change in diameter from baseline (%FMD). A one-way repeated measures ANOVA was used to determine if there were differences within %FMD, baseline and peak diameter over the five testing days. Reliability was determined using repeatability, calculated as (1.96 × &Sqrt;2) × within subject standard deviation, and the intraclass correlation coefficient (ICC).

RESULTS: There was no significant difference between the five tests for %FMD (Test1 3.3±2.1%; Test2 3.5±1.6%; Test3 4.8±1.8%; Test4 4.5±2.3%; Test5 4.5±2.0%), baseline diameter (Test1 6.7±0.7mm; Test2 6.7±0.5mm; Test3 6.7±0.6mm; Test4 6.5±0.5mm; Test5 6.7±0.5mm) or peak diameter (Test1 6.9±0.6mm; Test2 6.9±0.6mm; Test3 7.0±0.6mm; Test4 6.8±0.5mm; Test5 7.0±0.4mm). Nevertheless, %FMD measurements demonstrated poor reliability (Repeatability of 4.82%, ICC of 0.25), with repeatability values as large as the FMD measures themselves. Baseline and peak diameter measures were more reliable (Repeatability 1.00 and 1.32mm, ICC 0.62 and 0.52, respectively).

CONCLUSION: Popliteal artery FMD has poor stability reliability. Therefore, interpretation of group, and especially individual changes using this technique should be made with caution.

Supported by NSERC and Queen Elizabeth II Graduate Scholarship in Science and Technology

196 Board #48 May 29, 9:30 AM - 11:00 AM

Effects of Acute, Induced Inflammation on Cardiovascular Function

Abbi D. Lane1, Rebecca Kappus1, Kanokwan Bunsawat1, Sushant Ranadive2, Huimin Yan2, Shane Phillips1, Robert Motl2, Jeffrey Woods, FACSM2, Tracy Baynard1, Bo Fernhall, FACSM1. 1University of Illinois at Chicago, Chicago, IL. 2University of Illinois at Urbana-Champaign, Urbana, IL.

(No relationships reported)

Acute inflammation affects the cardiovascular system, causing vasodilation, reduced ventricular performance, and impaired endothelial function. Physical activity reduces inflammation and preserves cardiovascular performance. Arterial elastance (Ea), a composite measure of total afterload, and ventricular elastance (Elv), a surrogate for left ventricular performance, may be affected by acute inflammation. This is important, as Ea:Elv is a crucial determinant of blood pressure and cardiovascular reserve.

PURPOSE: We determined the effects of physical activity on ventricular and vascular function (Ea, Elv) following acute, induced inflammation.

METHODS: Aortic blood pressure and augmentation index (AIx) were obtained using applanation tonometry before and 24 and 48 hr after a flu shot. Ultrasonography was used to measure cardiac volumes. Ea was found using end-systolic pressure (ESP)/ stroke volume (SV) and Elv=ESP/end-systolic volume (ESV). Physical activity was measured with accelerometry and averaged over 5 days of wear time.

RESULTS: 29 young adults (19 males, age=25 yr completed the study. At 24 hr post-inflammation, Elv, ESP, and AIx were significantly reduced (p<0.05) compared to baseline. ESP and Elv returned to baseline levels at 48 hr hr post-inflammation (p>0.05 compared to baseline), while AIx remained significantly decreased (p<0.05). Ea was not affected (p>0.05). Physical activity volume was not related to these changes (p>0.05).

CONCLUSION: Acute inflammation impacts both vascular and cardiac performance in younger adults. Physical activity does not appear to be related to these functional changes in young adults.

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197 Board #49 May 29, 9:30 AM - 11:00 AM

The Influence of Skeletal Muscle Massage on Heart Rate Variability

Kyle T. Ebersole, Joshua K. Conlon, David J. Cornell, Matthew Bartz, Barbara B. Meyer. University of Wisconsin-Milwaukee, Milwaukee, WI. (Sponsor: Terry J Housh, FACSM)

(No relationships reported)

Prior studies have examined changes in heart rate as an autonomic nervous system outcome measure following skeletal muscle massage. Heart rate variability (HRV) is a non-invasive measure that may provide greater information than heart rate (HR) alone regarding the autonomic balance between sympathetic and parasympathetic systems.

PURPOSE: To examine the influence of massage on HRV.

METHODS: 18 healthy participants were placed into a massage group (n=9, 22.5±1.9 yrs, 66.3±11.4 kg) and control group (n=9, 23.2± 2.5 yrs, 68.0±10.6 kg). The massage group received a 15-minute massage to the posterior thigh and leg. The control group rested quietly for 15-minutes. Beat-to-beat interval (R-R) was recorded with a remote heart rate system. Post-hoc analysis of the R-R intervals determined the following time domain and frequency HRV parameters: HR, root mean square differences of the standard deviation (RMSSD), and low-frequency to high-frequency ratio (LF/HF). Prior to analysis, all ectopic beats were corrected using the interpolation method. Separate (HR, RR, RMSSD, LF/HF) repeated measures ANOVA’s examined within group changes from pre and post intervention. An alpha of p<0.05 was used to determine significance.

RESULTS: For the massage group, there was a significant decrease in HR (80 vs. 74 bpm), a significant increase in R-R (768.7 vs. 836.5 ms), but non-significant changes in RMSSD (39.8 vs. 56.0) and LF/HF (2.1 vs. 1.6 n.u.). For the control group, there was a significant decrease in HR (77 vs. 68 bpm), a significant increase in R-R (792.0 vs. 893.4 ms), but non-significant changes in RMSSD (48.6 vs. 61.0) and LF/HF (1.5 vs. 0.76 n.u.).

CONCLUSION: The decrease in HR and increase in HRV, as represented by the increased R-R interval, suggested that there was an increase in parasympathetic influence on the control of heart rate. Although not significant, the trend for changes in RMSSD and LF/HF were consistent with an autonomic balance favoring parasympathetic modulation. It is interesting to note that each condition, massage and quiet resting, elicited similar responses. Thus, it is possible that any autonomic changes following a short-duration, skeletal muscle massage may not necessarily be due to the actual massage, but more related to the time spent in rest.

198 Board #50 May 29, 9:30 AM - 11:00 AM

Limitations to VO2peak in Obese Women with Polycystic Ovary Syndrome

Antti-Pekka E. Rissanen1, Tiina Koskela-Koivisto1, Harriet Hägglund1, Anne S. Koponen1, Jyrki M. Aho2, Aila Tiitinen1, Heikki O. Tikkanen1, Juha E. Peltonen1. 1University of Helsinki, Helsinki, Finland. 2Foundation for Sports and Exercise Medicine, Helsinki, Finland.

(No relationships reported)

Obese women with polycystic ovary syndrome (PCOS) and insulin resistance (IR) have impaired cardiorespiratory fitness, demonstrated by reduced peak O2 uptake (VO2peak).

PURPOSE: To examine the contribution of central and peripheral mechanisms to the reduced VO2peak in obese PCOS women with IR.

METHODS: Ten obese PCOS women with IR (PCO) and ten healthy age-matched controls (CON) performed an incremental cycle ergometer test to determine VO2peak. Cardiac output (CO) and arterial O2 saturation (SpO2) were monitored, and central O2 delivery (QaO2 = CO × [Hb] × SpO2 × 1.34; [Hb] = hemoglobin concentration) and arterial-venous O2 difference (C(a-v)O2 = VO2 / CO) were calculated. Tissue oxygenation and changes in blood volume (i.e., relative concentration changes in total hemoglobin (Δ[tHb])) were locally monitored by near-infrared spectroscopy in active leg muscle, inactive arm muscle and cerebral tissue. Fasting venous blood was drawn for measurement of plasma glucose and serum insulin at a separate visit, and homeostasis model assessment index of IR (HOMA = fasting plasma glucose × fasting serum insulin / 22.5) was calculated. Group comparisons were made using independent samples t-test, and relationships between variables were determined by Pearson’s correlation.

RESULTS: Relative VO2peak was lower (25±4 vs. 33±7 mLmin-1kg-1, P<0.01) and HOMA was higher (2.3±1.1 vs. 1.0±0.5, P<0.05) in PCO than CON. In all subjects, relative VO2peak was inversely correlated with HOMA (r=-0.61, P<0.05). Body surface area -adjusted QaO2 (QaO2i) and C(a-v)O2 were 5 % and 8 % lower, respectively, in PCO than CON at peak exercise, but the differences missed significance (P>0.05). In addition, VO2peak tended to correlate with peak C(a-v)O2 (r=0.58, P=0.080) but not with peak QaO2i (r=0.13, P=0.731) in PCO. Leg muscle Δ[tHb] in PCO was lower throughout the exercise, and decreased earlier and more drastically at high work rates.

CONCLUSIONS: Impairment in peripheral O2 extraction, probably resulting from maldistribution of peripheral blood flow, but also in central O2 delivery seem to limit VO2peak in obese PCOS women with IR.

Supported by Tekes - the Finnish Funding Agency for Technology and Innovation (40043/07), the Ministry of Education and Culture, Helsinki University Central Hospital Research Funds, and Juho Vainio Foundation.

199 Board #51 May 29, 9:30 AM - 11:00 AM

Effects Of Exercise Training And Coenzyme Q10 Supplementation On Pentraxin-3 And Paraoxonase Activities In Aged Rats

Muaz Belviranlı1, Nilsel Okudan1, Ayşe Kumak1, Kısmet Esra Nurullahuglu-Atalık2, Mehmet Oz1. 1Faculty of Medicine, Selcuk University, Konya, Turkey. 2Meram Faculty of Medicine, Necmettin Erbakan University, Konya, Turkey.

(No relationships reported)

Pentraxin 3 (PTX3) is mainly produced by endothelial cells, macrophages, and smooth muscle cells in the atherosclerotic region and it has a cardioprotective effects. Exercise training and coenzyme Q10 (CoQ10) have also been known to propose cardioprotection. However, it has been little known about the combined effects of CoQ10 and exercise training on PTX3 levels and paraoxanase (PON1) activities in aged rats.

PURPOSE: To investigate the effects of regular swimming training and oral CoQ10 supplementation on PTX3 levels and PON1 activities in aged and young rats.

METHODS: Sixty-four male Wistar were mainly divided into two groups: young and aged. Each group was further divided into four subgroups: control, CoQ10, training and CoQ10 plus training. The CoQ10 supplemented groups received an oral administration of CoQ10 at doses of 300 mg kg-1 of body weight per day dissolved in corn oil for 8 weeks. Exercised rats were swam for 60 min/day, 5 days/week for 8 weeks. PTX3 levels and PON1 activities were analyzed in plasma samples. Statistical analysis were performed using three way ANOVA to examine the main effects of age, CoQ10 supplementation and training (2x2x2).

RESULTS:PTX3 levels were higher in CoQ10 supplemented and exercise trained young rats compared to another young groups and aged control group (P<0.05). The highest PTX3 level observed in CoQ10 supplemented and exercise trained young group. PON1 activities were higher in CoQ10 supplemented and exercise trained young rats compared to young controls (P<0.05). It was also lower in aged control, aged CoQ10 supplemented and aged trained groups compared to the CoQ10 supplemented and exercise trained young group (P<0.05).

CONCLUSIONS: Exercise training in combination with the coenzyme Q10 supplementation has a cardioprotective effects especially in young rats.

200 Board #52 May 29, 9:30 AM - 11:00 AM

Effect Of Ischemic Preconditioning Before Exercise On Performance And Oxidative Damages: A Role Of mitoKATP

C.C. Lin1, Y.Z. Lin1, S.P. Lubi2, Y.T. Pan1, H.I. Chen3. 1Nat’l Dong Hwa U., Hualien, Taiwan. 2Chinese Culture U., Taipei, Taiwan. 3Tzu Chi U., Hualien, Taiwan.

(No relationships reported)

PURPOSE: Ischemic preconditioning (IPC) on cardiomyocytes has

been proved its protective function against oxidative damages induced by a long time ischemia and enhancement of human exercise performance. To understand the mechanisms, this study constructed an animal model to investigate the IPC effect on exercise performance.

METHODS: Twenty male SD rats were randomly assigned to 4 groups: CON, 5-HD+IPC (5-hydroxydecanoic or 5-HD, a mitoKATP inhibitor, 5 mg/kg by i.p.,5 min before IPC), PIN (pinacidil, a mitoKATP opener, 50μg/kg by i.p.,5 min before exercise test). Rats were treated by IPC (5-min ischemia/5-min reperfusion, 3 repetitions) with a cuff pressure of 300 mmHg on proximal end of the rat tail and followed by a graded exercise test on treadmill. Exhaustion time was recorded and biochemical indicators of plasma were analyzed. One-way ANOVA was applied to test the difference and significance was set at p <.05.

RESULTS: As compared to CON, except for 5-HD+IPC, exhaustion time in IPC and PIN were significantly longer (21.2±1.5 min & 20.6±1.4 min vs. 18.5±1.4 min, p <.05). There were no differences among groups in lactate, glucose, NOx,TBARS of plasma; however, carbonyls protein was significantly lower in PIN than in CON (21.15±3.90 nmol/mg vs. 38.07±9.02 nmol/mg, p<.05).

CONCLUSIONS: We developed an animal model to investigate the positive effect of IPC on exercise performance and found a closely correlation with opening of mitoKATP.

201 Board #53 May 29, 9:30 AM - 11:00 AM

Downregulation Of [Latin Small Letter Open E]Pkc In Exercise Preconditioning Induced-Early Phase Of Cardioprotection In Rats

Zhe HAO, Shan Shan Pan. Shanghai University of Sport, Shanghai, China.

(No relationships reported)

Exercise preconditioning (EP) provides early cardioprotection against exhaustive exercise-induced myocardial injury is well kown; however, the mechanisms that underlie this phenomenon are unclear. Reports suggest that [Latin Small Letter Open E]PKC may be critical mediator in cardioprotective signaling pathways that protect the heart from myocardial injury.

PURPOSE: To view the changes of [Latin Small Letter Open E]PKC expression during the early phase protection induced by EP.

METHODS: SD rats were divided into control group(C), EE group, EEP group, EEP+EE group, LEP group, LEP+EE group. Rats were subjected to run on the treadmill for four periods of 10 min each at 30 m/min with intervening periods of rest of 10 min as an EP protocol. The exhaustive exercise was performed 0.5 h (EEP+EE group) or 24h (LEP+EE group) after EP. Western blotting method was used to detect changes of [Latin Small Letter Open E]PKC and the phosphorylation of [Latin Small Letter Open E]PKC (p-[Latin Small Letter Open E]PKC). Real-Time PCR was used to detect the mRNA changes of [Latin Small Letter Open E]PKC.

RESULTS: As compared with the group C, [Latin Small Letter Open E]PKC significantly increased (0.98±0.34 vs. 0.64±0.08, P<0.05) in group EE, but p-[Latin Small Letter Open E]PKC and [Latin Small Letter Open E]PKC mRNA did not change (1.14±0.25 vs. 1.18±0.24&3.94±0.53 vs. 4.02±0.17, P>0.05). As compared with the group C, [Latin Small Letter Open E]PKC significantly increased (1.10±0.13 vs. 0.64±0.08, P<0.05) in group EEP, but p-[Latin Small Letter Open E]PKC significantly decreased (0.60±0.13 vs. 1.18±0.24, P<0.05), [Latin Small Letter Open E]PKC mRNA did not change (3.40±0.67 vs. 4.02±0.17, P>0.05). While compared with the group EE, [Latin Small Letter Open E]PKC did not change (0.73±1.08 vs. 0.98±0.34, P>0.05) in group EEP+EE, but p-[Latin Small Letter Open E]PKC and [Latin Small Letter Open E]PKC mRNA significantly decreased (0.60±0.13 vs. 1.18±0.24&2.84±0.50 vs. 3.94±0.53, P<0.05).

CONCLUSIONS: [Latin Small Letter Open E]PKC in rat heart was upregulated after EP, but the p-[Latin Small Letter Open E]PKC was downregulated. Although the [Latin Small Letter Open E]PKC level was also high, p-[Latin Small Letter Open E]PKC and [Latin Small Letter Open E]PKC mRNA was not change in exhaustive exercise rat heart, and an acute myocardial injury occurred at the same time. EP could attenuated myocardial injury in early phase of cardioprotection, but either p-[Latin Small Letter Open E]PKC and [Latin Small Letter Open E]PKC mRNA was downregulated. These results suggest that the downregulation of the phosphorylation of [Latin Small Letter Open E]PKC and [Latin Small Letter Open E]PKC mRNA may play an important role in the early cardioprotective mechanism afforded by EP.

Supported by the National Natural Science Foundation of China (No. 31071031), the Science and Technology Commission of Shanghai Municipality (No. 09490503300)

202 Board #54 May 29, 9:30 AM - 11:00 AM

Does Arterial Health Influence Exercise Tolerance?

Miriam E. Pearman, Evan DeVallance, Sara Fournier, Daniel Bonner, David Donley, Brad Warden, W Gharib, Paul Chantler. West Virginia University, Morgantown, WV.

(No relationships reported)

Introduction: Aerobic fitness, as measured by VO2peak, is a well-validated predictor of morbidity and mortality in healthy individuals and those with cardiovascular disease. Resting arterial function, as indicated by carotid to femoral pulse wave velocity (cfPWV: arterial stiffness), and arterial structure as indicated by intima-media thickness (IMT), and carotid diameter (Dc), are correlated to cardiovascular risk. As alterations in arterial health likely impact aerobic capacity, identifying arterial parameters that predict cardiovascular fitness are necessary; however, this relationship has not been fully investigated.

PURPOSE: This preliminarily cross-sectional study examined the relationship between relative peak VO2 and resting arterial function of 51 subjects without overt cardiovascular disease (CVD) (mean age 44.9 ± 11.6).

METHODS: VO2peak was assessed using a staged graded exercise test on a semi-recumbent bicycle until volitional fatigue. cfPWV was measured with Applanation tonometry; IMT and Dc were measured with B mode ultrasound. To account for individual differences in CVD risk each individual was assigned a metabolic risk score based on their age, sex, blood pressure, BMI, triglycerides, HDL, and glucose.

RESULTS: Univariate regression models indicated that VO2peak is significantly related to cfPWV [r = -0.43, p = 0.002], IMT [r = -0.46, p = 0.001], and Dc [r = -0.30, p = 0.035]. For multivariate analysis adjusted for age, sex, and metabolic risk scores, VO2peak remained significantly related to cfPWV [r = -0.29, p = 0.036], IMT [r = -0.32, p = 0.012], and Dc [r = -0.25, p = 0.037].

CONCLUSION: Preliminary data suggest that peak oxygen uptake is independently correlated with arterial health in populations free of overt CVD. These results suggest that improving peak oxygen uptake may have a favorable effect on arterial function and vice versa.

203 Board #55 May 29, 9:30 AM - 11:00 AM

Physical Activity And Cardiac Changes Across The Lifespan In Mice With Surgically Sprained Ankles

Sophie B. Guderian, Tricia Hubbard-Turner, FACSM, Erik A. Wikstrom, FACSM, Michael J. Turner. UNC Charlotte, Charlotte, NC.

(No relationships reported)

Aging leads to negative changes in left ventricular (LV) structure and function. Physical activity can lead to positive cardiac remodeling that allows the LV to function more efficiently. Currently we do not know how musculoskeletal pathology affects physical activity levels and therefore LV structure. With musculoskeletal injury being so prevalent, especially ankle sprains, there is a need to examine how physical activity levels and LV function are affected.

PURPOSE: The purpose of this study is to investigate LV changes across the lifespan in mice with and without an ankle sprain.

METHODS: Thirty male mice (CBA/J) were randomly placed into one of three groups: the transected CFL group, the transected ATFL/CFL group, and a SHAM group. Three days after surgery, all of the mice were individually housed in a cage containing a solid surface running wheel and daily running wheel measurements were recorded (distance, duration, speed). Before and every 6 weeks after surgery, measures of LV structure were measured on all mice. LV structure was imaged using 2D M-mode echocardiography and Doppler ultrasound with a SONOS 5500 ultrasound and 15-6L ultrasound probe.

RESULTS: For the first 4 weeks after surgery mice in the ATFL/CFL group had significantly decreased physical activity levels compared to the SHAM group (distance p = .002; duration p = .01; speed p = .04). The average daily distance run was lowest in the ATFL/CFL group (2.71±1.18 km/d) compared to the CFL group (3.66±1.33 km/d) and greatest in the SHAM group (4.53±1.55 km/d, p= 0.021). Before surgery, there were no significant differences in LV end-diastolic dimension (EDD), posterior wall thickness (PWT) and fractional shortening (FS). Through 8 months of age there is no significant difference in EDD (p = .065). Beginning at 6 months of age there is significant difference in FS between the ATFL/CFL and SHAM group (p = .042). Additionally, PWT was significantly greater in the ATFL/CFL group beginning at 4 ½ months of age compared to the SHAM and CFL group.

CONCLUSIONS: Based on the current data, mice with more severe ankle sprains are showing some negative alterations in LV structure. These negative alterations are probably due to the significantly decreased physical activity levels in these mice. As the mice continue to age, further research will determine if these changes continue.

204 Board #56 May 29, 9:30 AM - 11:00 AM

Caffeine Augments The Prothrombotic Response To Acute Exercise

Paul Nagelkirk, Ashley E. Morris, Matthew Overstreet, Justin P. Guilkey. Ball State University, Muncie, IN. (Sponsor: Chris Womack, FACSM)

(No relationships reported)

Caffeine is considered the most commonly used psychoactive drug, and also a popular ergogenic aid. Caffeine induces vascular changes that are closely associated with thrombotic development, which typically precedes adverse cardiovascular events. Thus, caffeine may elevate thrombotic risk.

PURPOSE: The purpose of this study was to assess the influence of a single dose of caffeine on thrombotic potential before and after an acute bout of exercise.

METHODS: Nine healthy men (age 24.5 ± 2 yrs, BMI 23.7 ± 2 kg/m2) completed two trials separated by one week. Each trial began with the consumption of a beverage containing 6 mg/kg of caffeine (CAFF) or a placebo drink (PLAC), in random order. Subjects were blinded to the content of the drinks. One hour of seated rest was then completed, followed by a maximal exercise test on a cycle ergometer. Blood samples were obtained after the one-hour rest and immediately after exercise, and used to determine concentrations of fibrinogen and coagulation factor VIII antigen. The influence of caffeine on baseline measures and peak exercise data were assessed by paired t-test. The coagulation responses to exercise in the two trials were analyzed by ANOVA.

RESULTS: Resting SBP was higher in CAFF (123.7 ± 5.5 mmHg) than PLAC (113.4 ± 9.7 mmHg). No baseline differences were observed between CAFF and PLAC trials, respectively, for HR (60 ± 11.7 vs 62 ± 8.3 bpm), DBP (80 ± 12 vs 74 ± 10 mmHg), fibrinogen (221.5 ± 53.5 vs 255.8 ± 36.9 mg/dl), or factor VIII (1.0 ± 0.5 vs 0.9 ± 0.4 IU/ml). Peak HR (185.9 ± 11.9 vs 184.6 ± 11.2 bpm), and VO2 (50.6 ± 6.9 vs 52.7 ± 8.5 ml/kg/min) did not differ between CAFF and PLAC trials, respectively. A significant effect of time was observed for fibrinogen but there was no effect of trial or trial x time interaction (CAFF pre = 221.5 ± 53.5, post = 261.8 ± 48.9; PLAC pre = 255.8 ± 36.9, post = 286.9 ±44.5 mg/dl). Significant effects of time, trial and a time x trial interaction were observed for factor VIII. Factor VIII increased from 1.0 ± 0.4 to 3.4 ± 1.4 IU/ml in the CAFF trial and 0.9 ± 0.4 to 2.1 ± 0.8 IU/ml with PLAC.

CONCLUSION: Caffeine did not influence baseline coagulation activity. However, the factor VIII results suggest that increased thrombotic potential during exercise is augmented after caffeine intake. Results of this study suggest caffeine intake may increase cardiovascular risk during exercise.

205 Board #57 May 29, 9:30 AM - 11:00 AM

Is Normalizing Exercise-Induced Blood Flow for Muscle Mass Necessary?

Ryan S. Garten, H. Jonathan Groot, Matthew J. Rossman, Jayson R. Gifford, Russell S. Richardson. The University of Utah, Salt Lake City, UT.

(No relationships reported)

Previous research assessing the hyperemic response to single leg knee-extensor exercise has reported leg blood flow measurements both with and without normalization for muscle mass during submaximal exercise in an attempt to elucidate the relationship between muscle metabolism and leg hyperemia. Uncertainties about

the link between blood flow, relative effort, and muscle recruitment casts doubt on both approaches.

PURPOSE: This study sought to better understand the impact of quadriceps muscle mass (QMM) on common femoral artery blood flow (BF) during one-legged knee extension exercise at absolute submaximal workloads.

METHODS: Twenty-four healthy young males (27±4yrs) took part in this study. Common femoral artery BF was measured with an ultrasound Doppler during the last minute of three-minute stages (0W, 5W, 15W, and 25W) of one-legged knee extension exercise. Limb volume assessments were obtained both anthropometrically and with dual energy x-ray absorptiometry (DEXA) to determine thigh volume and QMM. Pearson correlations were utilized to identify the effect of QMM on BF at each specific workload. Coefficients of variation were calculated for the y-intercepts of the regression equations examining the relationship between each submaximal workload and the respective BF with and without QMM normalization.

RESULTS: QMM (2±0.3kg; range: 1.5-2.7kg) and BF were not significantly correlated at 0W (1453±313mL/min; p=0.4), 5W (1748±261mL/min; p=0.9), 15W (2416±382mL/min; p=0.8), or 25W (2934±475mL/min; p=0.6). The coefficients of variation of the y-intercepts (1476±287 vs 750±143) of the BF to workload relationships were not significantly different before and after normalization for QMM (19.5% vs. 19.1%; p=0.9).

CONCLUSIONS: Therefore, despite a wide range of QMM, normalizing for quadriceps muscle mass did not minimize the variance between subjects in the BF to submaximal workload relationship. This implies that muscle mass has no impact on exercise-induced BF and workload (metabolic demand) is likely the major determinant of the hyperemic response to exercise.

206 Board #58 May 29, 9:30 AM - 11:00 AM

Hindlimb Unloading Results In An Increased Predisposition To Cardiac Arrhythmias And Changes In Left Ventricular Connexin43 Expression

Julia A. Moffitt, Matthew K. Henry, Kathryn C. Welliver, Amanda J. Jepson, Emily R. Garnett. Des Moines University, Des Moines, IA.

(No relationships reported)

PURPOSE: Cardiovascular deconditioning produced through hindlimb unloading (HU) in rats, results in cardiac sympathovagal imbalance, which may increase arrhythmic risk. Changes in left ventricular (LV) expression and phosphorylation of connexin43 (Cx43) may also play a role in autonomic arrhythmogenesis. We hypothesized that HU would result in an increased predisposition to spontaneous and provoked (isoproterenol 0.15mg/kg, s.c, plus brief restraint) arrhythmias. We further hypothesized that LV Cx43 expression would be altered in HU rats.

METHODS: Radiotelemetry probes were surgically implanted in male, Sprague-Dawley rats using aseptic technique for collection of electrocardiographic data during the 10-14 day HU (n=6) or casted control (CC; n=6) protocol, at the end of the protocol in the normal posture at rest, and during an acute stressor. Arrhythmias were quantified by an established scoring method. In a separate group of HU (n=5) and CC (n=5) rats, total (phosphorylated and unphosphorylated) and unphosphorylated LV Cx43 protein expression was quantified by Western blot analysis using polyclonal and monoclonal antibodies, respectively and normalized to ERK as a loading control.

RESULTS: HU rats sustained significantly (p<0.05) more spontaneous arrhythmias during the protocol and had a higher arrhythmic burden during an acute stressor (CC: 19±3.5 vs. HU: 51±11) following HU. Furthermore, there was a 45% increase in LV Cx43 expression following HU as compared to CC animals, while there was no change in the expression of unphosphorylated LV Cx43.

CONCLUSIONS: These data taken together suggest that HU results in increased arrhythmogenesis and expression of phosphorylated LV Cx43. IOER-3726

207 Board #59 May 29, 9:30 AM - 11:00 AM

Effects of Flow-Mediated Shear Stress on Vascular Homeostasis: Implications on Mitochondrial Biogenesis and Microparticles Formation

Ji-Seok Kim1, Hojun Lee1, Boa Kim1, Brittany E. Wilson1, Keisuke Kawata1, Sunny Thakkar1, Michael D. Brown2, Joon-Young Park1. 1Temple University, Philadelphia, PA. 2University of Illinois at Chicago, Chicago, IL.

(No relationships reported)

The circulating level of endothelial microparticles (EMPs), a cellular biomarker for endothelial function, is increased in most cardiovascular diseases. While enhanced integrity of mitochondria has been recognized as an emerging protective mechanism against vascular complications, effects of laminar shear stress (LSS) and resveratrol (RSV), which both have been found to be potent Sirt1/PGC-1α activators, on endothelial mitochondrial biogenesis have not been studied.

PURPOSE: The purpose of this study was to test a hypothesis that LSS and/or RSV treatment on endothelial cells improves vascular homeostasis as determined by EMPs production.

METHODS: HUVECs were exposed to LSS (20 dyne/cm2 for 12h followed by 5 dyne/cm2 for 24h) using a cone and plate shear device. HUVECs were treated with 20 μM RSV for 12h. Immediately following LSS exposure, HUVECs were harvested for protein analysis and cell-culture media was collected for EMPs measurement. Rotenone (Rot) and Antimycin A (AA) were used as specific mitochondrial respiratory inhibitors for Complex I and III, respectively. Western blotting technique was used to analyze protein expression. EMPs (CD31+/CD42-) production was measured by flow cytometry.

RESULTS: The level of EMPs production was significantly increased by treatment of mitochondrial complex inhibitors (3.55±0.69 to 6.72±0.25 by Rot; 1.60±0.29 to 2.87±0.4 by AA; p<.05). However, EMPs production was dramatically decreased by following LSS treatment (1.97±0.40 by LSS after Rot; 1.21±0.24 by LSS after AA; p<.05), while expression level of Porin, a mitochondrial content marker, was significantly increased by LSS (0.63±0.02 to 6.83±0.27 by LSS after Rot; 0.14±0.015 to 2.56±0.53 by LSS after AA; p<.05). The expression levels of Sirt1 and PGC-1α, mitochondrial biogenesis factors, and Porin were dramatically increased by combined treatment of RSV/LSS, while the level of EMPs production was significantly decreased. Furthermore, the level of mitochondrial content increased by LSS and/or RSV was inversely correlated with the decreased level of EMPs production (r= -0.746, p=.005).

CONCLUSION: The present study demonstrated that LSS and/or RSV treatment improves vascular homeostasis by mitochondrial biogenesis in endothelial cells.

208 Board #60 May 29, 9:30 AM - 11:00 AM

Pneumatic Compression Acutely Increases Peripheral Artery Flow Mediated Dilation in Compressed and Non-Compressed Limbs

Jeffrey S. Martin1, M. Harold Laughlin, FACSM2. 1Lasell College, Newton, MA. 2University of Missouri, Columbia, MO.

(No relationships reported)

PURPOSE: We sought to evaluate the effects of a commercially available external pneumatic compression (EPC) device on peripheral artery flow mediated dilation (FMD) following 1-hour of dynamic lower limb compression.

METHODS: Eight (n=8) apparently healthy male subjects (32.6 ± 2.2 years of age), were recruited for participation in this study. In a crossover design, FMD of the popliteal and brachial arteries was evaluated before and after 1-hour of EPC and sham treatment, on separate days, in each subject. EPC consisted of sequential pulsation from feet to upper thighs/buttocks at approximately 70 mmHg. For sham treatments, subjects were placed in the compression leg sleeves, but no compression occurred. Treatment and peripheral artery FMD assessment order were randomized for each subject and an alpha level of 0.05 was required for statistical significance.

RESULTS: There was no effect of EPC or sham treatment on systolic (+0.5 ± 2.2 and -1.0 ± 2.1 mmHg for EPC and sham, respectively) or diastolic blood pressure (+2.5 ± 1.7 and +1.5 ± 1.5 mmHg for EPC and sham, respectively). Moreover, following EPC and sham, there was no change in baseline diameter of the brachial (-0.03 ± 0.04 and +0.05 ± 0.04 mm for EPC and sham, respectively) or popliteal (+0.09 ± 0.17 and -0.01 ± 0.11 mm for EPC and sham, respectively) arteries. EPC increased absolute, percent, and normalized FMD from baseline in the popliteal artery (+24.4%, +25.6%, and +56.5%, respectively), but there was no change following sham therapy (-9.8%, -9.1%, and -6.4%, respectively). EPC also increased absolute, percent, and normalized FMD in the brachial artery (+20.0, +20.3%, and +18.3% respectively) whereas there was no change following sham treatment (+5.6%, +4.4%, and +1.1%, respectively).

CONCLUSIONS: 1-hour of EPC acutely improves peripheral artery FMD in a compressed and non-compressed limb. We speculate that acute systemic improvements in nitric oxide bioavailability are a mechanism for the observed improvements.

Support for this project was provided by NIH T32-AR048523 (J.S.M.)

209 Board #61 May 29, 9:30 AM - 11:00 AM

The Effects Of Hydration Status On Pulse Rate And Heart Rate Variability During A Stand Test Of Orthostatic Tolerance

Lauren K. Buhr, Charles I. Stack, Maurie J. Luetkemeier. Alma College, Alma, MI.

(No relationships reported)

PURPOSE: This study examined changes in pulse rate and heart rate variability as indices of autonomic control following hypohydration and subsequent rehydration. Subjects: The participants (n=6; female=3, male=3) were athletes with an average age and weight of 23±13 years and 66.4±10.9 kg, respectively.

METHODS: The subject used moderately intense exercise for approximately 60-minutes to lose 3% of their body mass. For a 15-hour recovery period after the exercise, the participants were allowed to drink minimal fluids, i.e. 800-mL. The participants returned to the lab the next day to sequentially rehydrate with 3 equal portions of a carbohydrate/electrolyte beverage representing 1/3rd of the volume lost during dehydration. Pulse rate and heart rate variability were recorded for 7-min. of supine rest followed by 3 minutes of standing for each hydration state. Heart rate variability was subjected to a Fast Fourier transformation and a subsequent power spectrum density analysis resulting in a ratio of low to high power density. Since low power represents mainly sympathetic activity and high power represents vagal activity, the ratio of low:high is considered a good indicator of sympathetic-vagal balance.

RESULTS: Pulse rate increased significantly upon standing (57±2 to 71±3 beats/min). The changes in pulse rates from supine-to-standing tended to be greater before participants were allowed to rehydrate but were not significantly different between levels of rehydration, i.e., 18±3, 13±3, 11±5, and 11±4 beats/min, respectively. Likewise, heart rate variability rose significantly upon standing, i.e., 0.4±0.7 to 1.9±0.5. Heart rate variability tended to be greater before rehydration and declined progressively with each subsequent levels of rehydration, i.e., 3.5±1.5, 1.9±0.4, 1.5±0.5, and 0.7±0.2, respective. However, the heart rate variability was not statistically significantly different between levels of hydration.

CONCLUSIONS: Athletes in a dehydrated state tended to have higher changes in pulse rates and greater heart rate variability before rehydration indicating perhaps more sympathetic control of heart rhythm. During rehydration, the sympathetic nervous system control was less dominant over parasympathetic control when subjected to an orthostatic stand test.

210 Board #62 May 29, 9:30 AM - 11:00 AM

Autonomic Dysfunction In Women With Bulimia Nervosa, Women With Subthreshold Binge/purge Symptoms, And Asymptomatic Women

Jennifer Rogers, Katherine Blasko, MacKenzie Dreeszen, Jenna Moraski, Tara Ohrt, Christine Nguyen, Melinda A. Green. Cornell College, Mount Vernon, IA.

(No relationships reported)

Existing research on the biological correlates of binge/purge behaviors among women provides evidence of autonomic dysfunction including vagal hyperactivity and reduced sympathetic tone.

PURPOSE: To examine the relationship between autonomic dysfunction, neuroendocrine dysregulation, and binge/purge behaviors in a pilot sample of women with bulimia nervosa (BN), women with subthreshold levels of binge/purge behaviors (SubBN), and asymptomatic women (A).

METHODS: 31 female participants, 18-34 y, were recruited through community advertising (n = 7 BN, n = 8 SubBN, n = 16 A; 64.0 ± 13.0, 68.6 ± 21.1, and 70.5 ± 18.7 kg, respectively). Body composition (7-site skinfold), energy balance (3-day food, exercise, and binge/purge diaries), and neuroendocrine markers (blood assays for cortisol, epinephrine, norepinephrine, total estrogens, estradiol (E2), total testosterone, and free testosterone) were assessed. Autonomic indices were assessed via spectral analysis of heart rate variability at baseline (supine), during a deep breathing protocol, immediately following a posture shift, and in response to a static handgrip exercise protocol.

RESULTS: A one-way MANOVA detected group differences (BN, SubBN, A) in autonomic function (F (17, 8) = 2.90, p < .10, partial η2 = .86, observed power = .69, p < .10). Follow-up ANOVAs for each autonomic index indicated significant group differences for baseline HR (52 ± 14, 61 ± 7, 67 ± 10 bpm for BN, SubBN, and A, respectively, p < .05), HF power (p < .01), and LF/HF ratio (p < .05); diastolic BP (62 ± 5, 69 ± 9, 75 ± 8 mmHg, p < .05) and HR (57 ± 6, 68 ± 8, 75 ± 14 bpm, p < .05) after posture shifts; and diastolic BP after exercise (65 ± 6, 67 ± 8, 73 ± 7 mmHg, p < .05). Neuroendocrine indices did not partially mediate the relationship between binge/purge behavior and autonomic dysfunction.

CONCLUSIONS: Our data support previous findings of autonomic dysfunction (hypervagal tone, decreased sympathetic activation following physiological challenges from posture shifts, static handgrip exercise) occuring in women with bulimia nervosa and subthreshold binge/purge symptoms, compared with asymptomatic women. Future studies with larger sample sizes are warranted, particularly with regard to neuroendocrine dysregulation and autonomic dysfunction.

211 Board #63 May 29, 9:30 AM - 11:00 AM

Arterial Compliance in a Young Population

Christopher Mattson, Maleah Holland, Joel Stager, FACSM, Eric Ress. Indiana University, Bloomington, IN.

(No relationships reported)

Introduction: Small and large arterial compliance have been shown to be risk markers for cardiovascular disease in aging populations, with small arterial compliance as the superior predictor. In addition, physical activity has been shown to positively affect arterial compliance in aging populations. However, few data are available for arterial compliance in young, healthy individuals. The issue of whether or not the differences observed in older adults between the habitually highly active and the general population also exist in young adults between these groups remains unresolved.

PURPOSE: The purpose of this study is to contrast arterial compliance in college students who differ in levels of habitual physical activity.

METHODS: Based on self-reported vigorous physical activity questionnaires, 38 students, 24 men and 14 women, were categorized as highly active competitive varsity swimmers that work out roughly 20 hours per week (HA) (n=17; age 20.1 ± 1.3) or general population (GP) (n=21; age 20.9 ± 1.2). Resting cardiovascular measurements including large and small arterial compliance, blood pressure, and heart rate were recorded. Statistical analysis included two-sample t tests with p<0.05.

RESULTS: Because there were no differences between men and women for either activity group, data were pooled for remaining comparisons. No difference was found between GP and HA for large arterial compliance (GP 18.5 ± 3.8, HA 18.2 ± 4.0 mL/mmHgx10). However, HA had greater small arterial compliance values than the GP (HA 10.4 ± 2.5, GP 8.0 ±1.9 mL/mgHgx10). It should also be noted that there were no differences between the groups for systolic blood pressure (GP 121.8 ± 11.6, HA 126.3 ± 10.2 mmHg), diastolic blood pressure (GP 67.4 ± 7.9, HA 62.6 ± 5.3 mmHg) or pulse rate (GP 61.6 ± 6.7, HA 57.1 ± 8.1 bpm)

CONCLUSIONS:Small arterial compliance differs as a function of physical activity level even in college-aged people. This indicates that the effect of exercise reported for aging populations seems to exist in young populations as well. That small artery compliance is low in the less active young population should be of general concern as low small arterial compliance is recognized as an index of cardiovascular risk. These results also provide a baseline to which data from aging populations can be compared.

212 Board #64 May 29, 9:30 AM - 11:00 AM

Effects Of Upper Extremity Muscle Fatigue On The Heart Rate And Eeg During A Pistol Shooting

Jong Woo Ryu, Hyun Lyung Jung, Pan Soo Kim, Ho-Youl Kang. Kyungpook National University, Daegu, Republic of Korea.

(No relationships reported)

PURPOSE: The purpose of this study was to investigate the effects of upper extremity muscle fatigue on the heart rate and EEG during a pistol shooting.

METHODS: Eight elite male players (27.1 ± 2.7 yrs, 77.0 ± 3.6 kg, 172.6± 2.0 cm) with members of the national team volunteered for this study. The exercise repetitions for upper-extremity fatigue was individually determined at isokinetic machine at 7 days prior to experimental day. The isokinetic exercise was performed until the constant level of work output at speed of 120 ° / sec and the range of 10 ° ∼ 100 °. At the experimental day, all subjects performed the 3-set fatigue exercises with 60 s resting interval between sets and then immediately started the 10-m pistol shooting with 20 shoots for 300 s at the coach machine with heart rate and EEG monitors.

RESULTS: The shooting time and the aiming period were significantly decreased but the aiming distance was significantly increased after 3-set fatigue exercise when compared with those of non-fatigue status. The changes of thess variables due to fatigue exercise resulted in the significant deterioration of shooting score compared to pre-shooting score. After the fatigue exercise, the average heart rate was significantly increased, and also the fluctuation of heart rate was significantly reduced during shooing performance (pre = 6.8 vs post = , p < 0.05). EEG during shooting performance was determined at two areas(T3:left temporal lobe, T4:the right temporal lobe). The alpha wave at T3 of EEG was significantly elevated after fatigue exercise, but not at T4 of EEG.

CONCLUSIONS: The results of this study suggest that the muscle fatigue reduced the range of heart rate fluctuation and elevated the T3 of EEG with deteriorating shooting performance.

213 Board #65 May 29, 9:30 AM - 11:00 AM

Cardiac Dysfunction in the Tumor Bearing Rat

Traci L. Parry, Stephanie E. Greufe, Noah M. Gibson, David S. Hydock, Carole M. Schneider, FACSM, Reid Hayward. University of Northern Colorado, Greeley, CO.

(No relationships reported)

Cancer cachexia is a disease that affects up to 80% of cancer survivors and contributes to 20 to 30% of cancer deaths. It is characterized by weight loss, muscle atrophy, weakness, fatigue, and a diminished quality of life. While there is substantial evidence that cancer cachexia can lead to skeletal muscle wasting and weakness, its role in cardiac function is not well understood.

PURPOSE: To determine whether cardiac function is altered in the tumor bearing rat.

METHODS: Fisher 344 rats (8 weeks old) were randomly assigned to one of two groups: tumor-bearing (Tm) or non tumor bearing (NT). Animals in the Tm group were inoculated with MatBIII tumor cells (1 × 10^5) in the left flank. Animals in the NT group received no treatment. Two weeks later (week 10 of protocol), cardiac function was assessed both in vivo (echocardiography) and ex vivo (isolated perfused working heart).

RESULTS: The Tm group exhibited significantly (P < 0.05) lower left ventricular developed pressure, maximal rate of developed pressure, fractional shortening, and posterior wall thickness during systole and diastole compared to the NT group. The Tm group also exhibited significantly (P < 0.05) greater left ventricular rate of pressure decline, left ventricular diameter during systole and diastole, and ejection time compared to NT animals.

CONCLUSIONS: Inoculation with MatBIII tumor cells causes significant cardiac dysfunction both in vivo and ex vivo in the Fisher 344 rat, suggesting that cancer cachexia can affect cardiac function.

214 Board #66 May 29, 9:30 AM - 11:00 AM

Comparison Of Gene Expression, Protein Abundance, And Network Clusters In Young And Old Physically Inactive And Regular Exercising Rats

Helaine M. Alessio, FACSM, Hayden Ansinelli, Threadgill L. Caitlyn, Ann E. Hagerman. Miami University, Oxford, OH.

(No relationships reported)

Life-long physical inactivity has been reported to influence health-related phenotypes, in part, by up- or down-regulating gene expressions and associated proteins linked to age-related diseases. On the other hand, regular exercise is believed to prevent or mitigate the same diseases. Effects of the timing and amplitude of differentially expressed genes (DEGs) and changes in protein levels over a lifetime of either physical inactivity or regular exercise, is unclear.

PURPOSE: In this study we compare global gene expressions, qPCR, and two-dimensional differential gel electrophoresis (2D-DIGE) followed by mass spectrometry (MS) in cardiac tissue of young and old physically inactive animals with age-matched controls that regularly exercised on a running wheel.

METHODS: Male Sprague-Dawley rats (n=72) were evenly divided into SED (standard laboratory cage) and EX (running wheel inside standard cage). At 3-months, and at 16-months, animals were sacrificed at rest. RNA was extracted from cardiac tissue. Genes and gene networks associated with age-related diseases were identified via microarray, qPCR, and follow up analyses of gene maps and clusters. 2D-DIGE and MS, and use of the Database for Annotation, Visualization and Integrated Discovery, identified proteins and clusters in the same tissue.

RESULTS: Significant differences (FC >1.5 or <-1.5, p < 0.05) in gene expression only occurred between young and old animals in both SED and EX. DEG’s and gene clusters directly associated with age-associated diseases were observed in SED old vs young, but not EX old vs. young. DEG’s and clusters associated with muscle development, metabolic, and cardiac function, were reported in EX old vs young. 103 proteins were distinguished from 2D-DIGE and MS, and 58 were identified and found to differ in abundance and appear in clusters, with healthy functions favoring EX vs. SED.

CONCLUSION: Cardiac gene expressions in old v young physically inactive rats were more likely than regular exercisers, to be associated with specific proteins and networks linked to age-associated diseases.

Supported by NIA grant R15 AG029653-01.

215 Board #67 May 29, 9:30 AM - 11:00 AM

Determination of Repetitive Jumping Intensity Relative to Measured VO2max

Thomas S. Lyons, Gina S. Evans, Mark A. Schafer, Scott W. Arnett, Laura Igaune. Western Kentucky University, Bowling Green, KY.

(No relationships reported)

PURPOSE: Cardiorespiratory endurance is considered to be the most important element of aerobic fitness. In addition to regular exercise and a healthy diet, the American Heart Association (AHA) strongly recommends rope jumping, and according to previous studies, rope jumping is considered a very strenuous exercise. Therefore the purpose of this study was to determine the steady state metabolic cost of repetitive jumping on the Digi-Jump machine, and to determine if exercise on this device is more or less strenuous than similar exercise with a jump rope. Relative intensity of this type of exercise, based on each person’s VO2max as measured on a treadmill, was also evaluated.

METHODS: Twenty - seven subjects completed two trials, one jumping trial at a rate of 120 jumps per minute (JPM) with the jump height set at .5 inch for 5 min, and one graded exercise test (GXT) using the Bruce protocol. Oxygen uptake (VO2), heart rate (HR), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) were measured each minute during each trial.

RESULTS: Results of this study indicated that steady state VO2 during the 5 min jump test was reached during the 3rd min (p<.05). Therefore we evaluated all other variables (HR, RE, RPE) to be at steady state during the 3rd min. Average jumping steady state VO2 was 31.1 ± 5.5 ml/kg/min, while average VO2max was 56.4 ± 12 ml/kg/min, thus steady state VO2 during the jumping trial was 57.1% of VO2max. Average jumping steady state HR was 149. 2 ± 20.1 bpm, while mean GXT HR was 184.7 ± 9.9 bpm, thus steady state HR during the jumping trial was 80.9% of their maximal HR obtained during GXT. Average jumping steady state RER was .99 ± .6, while average GXT RER was 1.15 ± .07, thus steady state RER during the jumping trial was 86%, and average jumping steady state RPE was 13.5 ± 1.5, while average GXT RPE was 17.9 ± 1, thus steady state RPE during the jumping trial was 75.2%.

CONCLUSIONS: These data indicate that repetitive jumping on the Digi-Jump machine is a moderate intensity activity and may be used for aerobic fitness, though previous research has indicated that rope skipping may provide more strenuous aerobic exercise.

216 Board #68 May 29, 9:30 AM - 11:00 AM

Relationship Of Central Venous Pressure To Hemodynamic Responses During Lower Body Negative Pressure And Hemorrhage

Blair D. Johnson1, Noud van Helmond2, Timothy B. Curry1, Victor A. Convertino3, Michael J. Joyner1. 1Mayo Clinic, Rochester, MN. 2Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands. 3US Army Institute of Surgical Research, Fort Sam Houston, TX.

(No relationships reported)

Central venous pressure (CVP) is used as a marker of central blood volume, which influences stroke volume (SV), heart rate (HR), cardiac output (CO), and mean arterial pressure (MAP). Lower body negative pressure (LBNP) is a non-invasive method of inducing central hypovolemia and is used to study hemorrhage (HEM) in humans. However, a methodical assessment of the relationship of CVP to other hemodynamic responses during LBNP and HEM is lacking.

PURPOSE: To determine the relationship of CVP to SV, SV variation (SVV), HR, CO, and MAP during LBNP and HEM in conscious humans.

METHODS: We assessed CVP, SV, SVV, HR and CO in 6 men during LBNP and HEM. LBNP consisted of 5-minute stages at 0, -15, -30, and -45 mmHg of pressure. After 45 minutes of resting recovery from LBNP, the HEM protocol began and included 5 minutes at baseline and following three stages of 333 mL of hemorrhage (1 L total). The amalgamated r 2 was calculated using the mean value at each stage. Individual r 2 values were calculated to display inter-subject variability.

RESULTS: Throughout the LBNP protocol, CVP ranged from -3.6 to 12.8 mmHg, SV varied from 64 to 158 ml/beat, HR ranged from 52 to 118 bpm, CO varied from 6.1 to 10.3 L/min, and MAP ranged from 52.3 to 101.8 mmHg. Throughout the HEM protocol, CVP ranged from -2.2 to 10.3 mmHg, SV varied from 85.2 to 190.1 ml/beat, HR varied from 47 to 84 bpm, CO varied from 5.6 to 11.5 L/min, and MAP varied from 40.7 to 104.4 mmHg.

Amalgamated r2 for the relationship of CVP to each variable and the range of r2 values

Amalgamated r2 for the relationship of CVP to each variable and the range of r2 values

CONCLUSION: Despite mostly moderate to high amalgamated r 2 values, the relationship of CVP to hemodynamic variables which may be influenced by central hypovolemia is widely variable between subjects and between LBNP from 0 to -45 mmHg and throughout 1 L of HEM.

Funding: US Army MRMC Combat Casualty Care Research Program (Grant # W81XWH-11-1-0823).

217 Board #69 May 29, 9:30 AM - 11:00 AM

Use of Phase-rectified Signal Averaging to Examine Autonomic Dysfunction After Concussive Head Trauma

Michael F. La Fountaine1, William A. Bauman2. 1Seton Hall University, South Orange, NJ. 2James J. Peters VA Medical Center, Bronx, NY.

Phase rectified signal averaging (PRSA) is a technique to quantify the acceleration (AC; i.e., tendency to speed up) and deceleration capacity (DC; i.e., tendency to slow down) of a non-stationary signal, such as heart rate (HR). Recent research has demonstrated that both AC and DC are sensitive metrics of vagal modulation of sinoatrial (SA) pacing of HR. Autonomic dysfunction (AD) is a transient consequence of the post-concussive milieu with abnormal HR variability and QT interval variability index being demonstrated during provocation and at rest, respectively. The exact etiology of the post-concussive AD has yet to be defined and the clinical implications are not fully understood.

PURPOSE: To determine the sensitivity of PRSA analysis during acute-concussion injury in relation to vagal modulation during a low-intensity physiological challenge.

METHODS: Within 48 hours of injury presentation, a 3-minute isometric handgrip test (IHGT) was performed in the seated upright position on 3 concussed athletes (CA) and 3 gender, age, height, weight and sport matched controls (MC). HR was continuously monitored via 3-lead electrocardiogram (ECG) for 5 minutes preceding and during the IHGT. PRSA analysis was performed on the RR interval to obtain the AC and DC, the ratio between DC:AC was calculated to provide a single outcome of vagal activity. Separate unpaired t-tests were performed to determine the presence of group differences in demographics, DC:AC ratio and HR at rest and during the IHGT.

RESULTS: The groups were matched for demographics, while resting HR and DC:AC were not statistically different. During the IHGT in CA compared to MC, a non-significant attenuation in HR was observed (60±5 vs. 66±7, respectively) and DC:AC trended toward a significant difference (p=0.08; -1.4±0.4 vs. -0.8±0.1, respectively).

CONCLUSION: These preliminary findings suggest that vagal activity is more robust in pacing HR during a physiological challenge in CA compared to MC within 48 hours of injury. This elevation could partially explain the lower observed HR in the CA and indicate the presence of an attenuated capacity to withdraw vagal control of SA pacing of HR, with the latter expected to occur during a physiological challenge. The PRSA outcomes suggest that the primary AD in acute concussion injury may be vagal in origin.

© 2013 American College of Sports Medicine