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Browsing by Author "Williams, Jay H."

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    Acid-base regulation during exercise in the horse
    Ferrante, Pamela L. (Virginia Tech, 1994-01-15)
    Effects of fat adaptation and NaHC0₃ supplementation on acid-base homeostasis were quantitated during repeated sprint exercise in horses. Contribution of strong ions ([SID]), Pco₂, and weak electrolytes ([Atot]) to changes in plasma [H⁺] and the role of erythrocytes in acid-base balance were examined at rest and during exercise. Effects on plasma glucose and blood lactate [Lac⁻] concentrations due to sample handling were also assessed. During exercise, blood [Lac⁻] was higher when horses received NaHC0₃ compared to water prior to exercise (P=0.0024), and in fat adapted horses compared to horses fed a control diet (P=0.0240). Blood [Lac-] was higher in fat adapted horses given NaHC0₃ compared to other diet/treatment combinations (P=0.0276). Plasma [SID] was higher during exercise when horses were given NaHC0₃ compared to plain water (P=0.0054), which contributed to decreasing [H⁺] and increasing [HC0₃⁻] during exercise (P=0.0001). Plasma Pco₂ contributed less to increasing plasma [H⁺] during exercise in fat-adapted horses compared to horses fed the control diet (P=0.0282). Intraerythrocyte [SID] decreased (P=0.0160) and [Atod increased (P=0.0002) which contributed to increasing [H⁺] within the cell (P=0.0228).
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    The activity and content of calpains in maturing dystrophic muscle membranes
    Wang, Qiong (Virginia Tech, 2005-05-11)
    Increased calcium-activated calpain proteolysis in the sarcolemma membrane is thought to be a primary mechanism in the pathophysiology of Duchenne Muscular Dystrophy (DMD). However, few studies have tested this possibility prior to the overt signs of the dystrophy. The purpose of this study was to test the hypothesis that there is greater calpain content and total relative calpain activity in membranes obtained from dystrophic (mdx; mdx:utrophin-deficient (mdx:utrn-/-)) compared to wildtype (wt) mouse skeletal muscles during maturation at ages 7- and 21-d,and at a post-maturation age of 35-d. Calpain activity was determined as the calcium-dependent cleavage of the flurogenic substrate SLY-AMC, and content was determined by Western analysis with an anti-calpain antibody. There were several intriguing findings: 1. There was an inverse relationship between calpain content and relative activity in the whole muscle in both wt and mdx mice from age 7- to 35-d: calpain content decreased, and relative calpain activity increased as the mice aged. This suggests a similar role for calpain in both genotypes, which might relate to specific maturation processes, possibly up to age 21-d. Although the inverse relation was evident at 35-d, the targets for calpain in mdx compared to wt likely differed. 2. The increased relative calpain activity in the membrane fraction of mdx mice at age 35-d (26.73 Arbitrary Units, (AU)) compared to that of age 7- (4.9AU; p<0.05) and 21-d (8.74AU; p<0.05) is temporally related to degeneration and regeneration processes, and may also indicate activation of apoptosis, in mdx muscles at this age. 3. At age 7-d, there were no significant differences in either calpain content or relative calpain activity in all subcellular fractions for wt and mdx mice. This result might suggest similar calpain distribution and activities that are related to the regulation of muscle maturation and differentiation in both genotypes. (Note:data were not obtained for the mdx:utrn-/- mice at age 7-d because of insufficient animals). 4. At age 21-d, there was greater relative calpain activity in the myofibrillar supernatant fraction in mdx (15.13AU) than wt mice (1.18AU; p<0.05). This could indicate calpain's role in the initiation of myofibrillar protein turnover and the proteolysis of submembranous networks in the mdx muscles. 5. At age 21-d, greater calpain content in the mdx (1.40ìg) compared to wt (0.23 ìg; p<0.05) membrane fraction might suggest a broader distribution of calpain along membranes that contributes to the onset of dystrophy in the mdx muscles. 6. At age 35-d, there was greater calpain content in the mdx:utrn-/- compared to the wt membrane (0.48ìg vs 0.13 ìg), cytosolic (0.88ìg vs 0.30ìg), and myofibrillar supernatant (0.49ìg vs 0.17ìg; p<0.05 ) fractions This increased content and broad distribution across several subcellular fractions may reflect degeneration and regeneration processes, and potentially activation of apoptosis, in the mdx:utrn-/- muscles. These data suggest that calpain activity contributes to dystrophic pathophysiology mainly in the membrane fraction of mdx skeletal muscles at age ~21-d, but appears to contribute later at 35-d and in more subcellular fractions in mdx:utrn-/- skeletal muscles.
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    Athlete Monitoring in American Collegiate Football
    Lewis, Marc Theron (Virginia Tech, 2021-03-17)
    American football is one of the most popular sports in the United States. However, in comparison to other mainstream sports such as soccer and rugby, there is limited literature using scientific principles and theory to examine the most appropriate ways to monitor the sport. This serves as a barrier to American football practitioners in their development and implementation of evidence-based sport preparation programs. Therefore, the primary aim of this line of research (i.e., dissertation) is to illustrate the efficacy of commonly used athlete monitoring tools within the sport of American collegiate football, while proposing a systematic framework to guide the development of an athlete monitoring program. This aim was achieved through a series of studies with the following objectives: 1) to quantify the physical demands of American collegiate football practice by creating physiological movement profiles through the use of integrated microtechnology metrics and heart rate indices, 2) to determine the positional differences in the physical practice demands of American collegiate football athletes, 3) to examine which integrated microtechnology metrics might be used to most efficiently monitor the training load of American collegiate football athletes, 4) to demonstrate the suitability of using the countermovement jump (CMJ) to assess training adaptations in American collegiate football athletes through examining weekly changes in CMJ performance over the course of two 4-week periodized training blocks (8 weeks total), and 5) to examine the effect of acute fatigue on CMJ performance in American football athletes. The first study from this line of research quantified the physical demands of American collegiate football by position groups and found significant differences in both running based and non-running based training load metrics. In addition, the first study utilized a principal component analysis to determine 5 'principal' components that explain approximately 81% of the variance within the data. The second study utilized a univariate analysis and found significant changes in CMJ performance due the effect of time with significant improvements in CMJ 'strategy' variables over the training period. Finally, the third study used effects sizes to illustrate a larger magnitude of change in CMJ 'strategy' variables than CMJ 'output' variables due to effect of acute fatigue. Results from studies 2 and 3 suggest the importance of monitoring CMJ strategy variables when monitoring training adaptations and fatigue in American collegiate football athletes. This line of research provides practitioners with a systematic framework through which they can develop and implement evidence-based sport preparation programs within their own organizational context. In addition, this line of research provides practitioners with recommendations for which metrics to monitor when tracking training load in American collegiate football using integrated microtechnology. Finally, this line of research demonstrates how to assess training adaptations and fatigue using the CMJ within the sport of American collegiate football, while providing an empirical base through which the selection of CMJ variables can take place. Collectively, this line of research uses scientific principles and theory to extend the current literature in American collegiate football, while providing practitioners with a guide to athlete monitoring within the sport.
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    Cardiorespiratory responses to altered rider position with conventional and aerodynamic handlebars
    Betz, Christopher Brian (Virginia Tech, 1990-07-06)
    This investigation evaluated the cardiorespiratory responses to three rider positions while undergoing maximal cycle ergometry. The positions were determined by the position of the hands on the handlebars and the posture of the upper body: upright (UP), and drop position (DP) with conventional racing handlebars, and an aerodynamic tuck (AT) using Scott DH time-trial handlebars. Ten well-trained (mean V02max=60.7 ± 3.63 ml*kg-1*min-1) cyclists underwent three randomly assigned separate maximal ergometry tests using each position. Variables of interest were: heart rate (RR), systolic blood pressure (SBP), diastolic blood pressure (DBP) , rate pressure product (RPP) , oxygen consumption (V02), pulmonary ventilation (VI)' ventilatory equivalent (V1/V02), respiratory exchange ratio (RER), ratings of perceived exertion (RPE) , and total time to test termination (TT). These variables did not differ significantly between rider positions at each stage of the maximal exercise tests but did change in response to increasing workloads. These results suggest that rider position does not enhance or diminish the cardiorespiratory response to maximal cycle ergometry as the responses to each position are similar.
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    Changes in Skeletal Muscle Sarcoplasmic Reticulum Calcium Handling and Regulatory Protein Content in Congestive Heart Failure
    Allen, Emily E. (Virginia Tech, 2002-04-17)
    Fatigue and skeletal muscle weakness are problems associated with congestive heart failure. Research does not support the theory that the affected cardiac function is responsible for the fatigue. During skeletal muscle fatigue, calcium handling is altered. Thus, the fatigue associated with congestive heart failure could be attributed to altered calcium handling. The main proteins involved in calcium release are the ryanodine receptor (RyR) and the dihydropyridine receptor (DHPR). The main proteins involved in calcium uptake are the fast and slow isoforms of sarco(endo)plasmic reticulum calcium ATPase (SERCA 1 and SERCA 2 respectively). Calsequestrin (Csq) and calmodulin (CaM) play regulatory roles in calcium handling. Changes in the levels of these proteins could explain alterations in calcium handling and subsequent muscle function. The purpose of this study was to use a genetic model of heart failure, the SHHF rat, to examine the levels of regulatory calcium handling proteins to determine if changes in the amounts of RyR, DHPR, SERCA1, SERCA2, Csq and CaM are altered in congestive heart failure. A significant decrease was found in the amounts of RyR, DHPR, and SERCA 1 of the SHHF gastrocnemius and diaphragm samples in comparison to the control. There was no significant difference found in the amounts of CaM or SERCA 2 between the two groups. Csq was not found to be statistically different between the two groups of the gastrocnemius samples. However, there was an increase in Csq in the SHHF diaphragm samples in comparison to the control. In conclusion, the calcium handling proteins are affected in the genetic model of heart failure. These changes could explain previous reports of altered calcium handling within the skeletal muscles of congestive heart failure animals.
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    Changes in Skeletal Muscle Sarcoplasmic Reticulum Function in Adult and Aged Fisher 344 Brown x Norway Rats
    Rabon, Karma Melisa (Virginia Tech, 1997-06-16)
    The decline of physical ability that occurs with aging has been linked to reduced skeletal muscle function. It has been theorized that Ca2+ uptake and release by the sarcoplasmic reticulum (SR) is altered with aging. Data pertaining to the actual structural and functional changes of SR due to aging are limited; thus, this theory has not yet been fully proven. The purpose of this research was to determine if SR function is altered as a result of aging in the following muscles: soleus, plantaris, and diaphragm. The soleus is composed of slow twitch muscle fibers. The plantaris is composed of fast twitch muscle fibers, and the diaphragm is composed of both slow and fast twitch muscle fibers. Fisher 344 Brown x Norway Cross Rats were used as subjects for this project. A total of 12 animals were used: six in group 12 months and six in group 27 months. A Jasco CAF-110 Fluorometer and fura-2 were used to determine the rate of Ca2+ uptake and release by isolated SR vesicles. In the aged animals, mass of the soleus was reduced by 22%, while the plantaris was reduced by 23%, and the diaphragm by 15%. However, these differences were eliminated when masses were normalized by body mass. In all three muscles examined, the rates of Ca2+ uptake were not significantly different between the young and aged animals. Rates of Ca2+ release, however, were reduced by 30% in both the plantaris and diaphragm of the aged animals. These results suggest that SR function is altered in "fast" muscles of the rat. It is possible that changes in SR Ca release may contribute to diminished muscle function and also lead to the decline in physical ability of older adults.
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    Complementary use of wearable technology 1: A data comparison of two platforms
    Williams, Jay H.; Rizzuto, Samuel F.; Whitaker, Emily J.; Dillard, Brandon A. (2021-07-01)
    Sports teams have at their disposal a vast array of wearable technology to assist in monitoring training loads and to assess rehabilitation. In particular, global positioning (GPS) and accelerometry have been incorporated into devices that can be positioned at different locations in the body (e.g. trunk, wrist, ankle and foot). With access to multiple devices and different analysis platforms, can multiple devices provide more insight into athlete monitoring? Are we measuring different things or simply exploring redundancies?
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    Complementary use of wearable technology 2: A case study in gait symmetry
    Williams, Jay H.; Rizzuto, Samuel F.; Whitaker, Emily J.; Dillard, Brandon A. (2021-09-01)
    The goal of this investigation was to demonstrate the usefulness of combining wearable technology devices to gain a more complete understanding of gait symmetry. To accomplish this, we examined gait symmetry in an athlete during rehabilitation from anterior cruciate ligament (ACL) reconstruction.
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    Complementary Use of Wearable Technology 3: Temporal Alignment and Similarity Measures of Accelerometer Signals from Two IMU Devices
    Williams, Jay H.; Rizzuto, Samuel F.; Dillard, Brandon A.; Whitaker, Emily J. (2022-06-01)
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    Complementary Use of Wearable Technology 4: Assessing Gait Asymmetry and Shock Attenuation Using Multiple IMU Devices
    Williams, Jay H.; Rizzuto, Samuel F.; Dillard, Brandon A.; Whitaker, Emily J. (2022-06-01)
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    Contractile Performance and Energy Utilization of Skeletal Muscle; Creatine Kinase and Acto-myosin ATPase
    Melnyk, Jason Alexander (Virginia Tech, 2009-01-23)
    Creatine kinase (CK) primarily serves as an energy buffer assisting in regulating ATP homeostasis through synthesis of ATP from ADP and phosphocreatine (PCr). This enzyme is bound in the sarcomere near sites of ATP consumption via acto-myosin ATPase (A‧M‧ATPase) and research in cardiac muscle has found that PCr can alter contractile performance (maximal isometric force and Ca²⁺ sensitivity). Based on this evidence, CK and A‧M‧ATPase may be coupled in skeletal muscle. Therefore the purpose of this investigation was to determine the influence of the CK system on contractile performance and energy utilization in skeletal muscle. When skinned fibers (membrane removed) were provided a limited supply of [ATP] (0.1 mM), this resulted in increased Ca²⁺ sensitivity. The addition of PCr to low ATP solutions restored Ca²⁺ sensitivity and allowed normal isometric force generation across a range of [Ca²⁺] via ATP synthesis by CK. This was also possible with only CK reaction substrates (ADP, PCr) in the absence of ATP. Based on these findings, endogenous CK activity in glycerol skinned skeletal muscle fibers is sufficient to permit normal function of the contractile apparatus. Energy utilization was studied by indirect assessment of ADP production. Decreased net ADP production as measured by NADH fluorescence revealed endogenous CK was able to convert ADP produced by A‧M‧ATPase to ATP in skeletal muscle across a range of both [Ca²⁺] and [ATP]. This was confirmed directly via high-performance liquid chromatography measurements of ATP and ADP by showing that skinned skeletal muscle bundles have sufficient endogenous CK activity to produce ATP from substrates (ADP, PCr) and the ability to maintain low [ADP] in the presence of PCr. This study adds to the evidence for specific compartmentation of CK near sites of ATP utilization and contributes to the body of knowledge on contractile performance in skinned skeletal muscle fibers. By showing how changing demands on skeletal muscle (through increased Ca²⁺) alters force production and Ca²⁺ sensitivity, these findings lend support for the importance of endogenous CK as a pathway of ATP regeneration in skeletal muscle.
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    Designing a Return to Activity Protocol for a Proximal Hamstring Rupture in a Collegiate Heptathlete: A Case Study
    Locus, Alaina; Williams, Jay H.; Anderson, Angela S.; Speicher, Logan (Virginia Tech, 2021-04-20)
    There are few return-to-activity protocols and functional tests specifically designed for a proximal hamstring rupture for athletic trainers to follow when clearing an athlete for return to activity. To address this problem, the purpose of this study is to describe and evaluate a return to activity protocol that includes functional testing for a post-surgical proximal hamstring rupture to assess readiness for return to activity. This case study collected data from a 20-year-old, 6ft 2in, 185lb (87.9 kg) collegiate heptathlete that ruptured his proximal hamstring that required surgical treatment. The student athlete’s (SA) return to activity process is evaluated and explained. The SA went through numerous function tests to determine return to activity status. The first testing session was conducted 8 months post-surgery. He was then re-assessed 4 months later. During testing, the SA also wore accelerometers to gather more quantitative data to identify gait abnormalities due to the injury. The first round of testing revealed greater strength in his left (affected) leg compared to his right (unaffected) leg. The SA was not able to complete all the tests during the first round of testing due to muscular fatigue and soreness, suggesting low muscular endurance at that point in time. Thus, he was not cleared to return to activity and continued to do rehabilitation exercises to increase the endurance of the hamstring muscles. The second round of testing was completed 4 months later which revealed that he had gained endurance in the hamstring muscles and his strength had increased. At this point, he was cleared for full return to activity. This return-to-activity protocol with specific functional tests could serve as a template for other athletic trainers who are seeking to return an athlete to full activity after suffering a proximal hamstring rupture (See Appendix I).
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    Detecting Transient Changes in Gait Using Fractal Scaling of Gait Variability in Conjunction with Gaussian Continuous Wavelet Transform
    Jaskowak, Daniel Joseph (Virginia Tech, 2019-01-31)
    Accelerometer data can be analyzed using a variety of methods which are effective in the clinical setting. Time-series analysis is used to analyze spatiotemporal variables in various populations. More recently, investigators have focused on gait complexity and the structure of spatiotemporal variations during walking and running. This study evaluated the use of time-series analyses to determine gait parameters during running. Subjects were college-age female soccer players. Accelerometer data were collected using GPS-embedded trunk-mounted accelerometers. Customized Matlab® programs were developed that included Gaussian continuous wavelet transform (CWT) to determine spatiotemporal characteristics, detrended fluctuation analysis (DFA) to examine gait complexity and autocorrelation analyses (ACF) to assess gait regularity. Reliability was examined using repeated running efforts and intraclass correlation. Proof of concept was determined by examining differences in each variable between various running speeds. Applicability was established by examining gait before and after fatiguing activity. The results showed most variables had excellent reliability. Test-retest R2 values for these variables ranged from 0.8 to 1.0. Low reliability was seen in bilateral comparisons of gait symmetry. Increases in running speed resulted in expected changes in spatiotemporal and acceleration variables. Fatiguing exercise had minimal effects on spatiotemporal variables but resulted in noticeable declines in complexity. This investigation shows that GPS-embedded trunk-mounted accelerometers can be effectively used to assess running gait. CWT and DFA yield reliable measures of spatiotemporal characteristics of gait and gait complexity. The effects of running speed and fatigue on these variables provides proof of concepts and applicability for this analytical approach.
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    The Development of a Conceptual Framework for Identifying Functional, Expressive, Aesthetic, and Regulatory Needs for Snowboarding Helmets
    Chae, Myung-Hee (Virginia Tech, 2006-11-10)
    The purpose of this research was to identify the design characteristics and attitudes that impact the use of snowboarding helmets and to test statistically a proposed conceptual framework for identifying perceived importance of functional, expressive, aesthetic, and regulatory (FEAR) needs of snowboarding helmets for current snowboarders. Data for this study was collected online. The final sample was composed of 391 participants, which represented a 13.67% response rate. Multiple comparisons were used to examine mean differences among the FEAR variables, as well as attitudes toward helmet use. A multiple linear regression was used to test four proposed hypotheses. The results of hypotheses revealed that there was an impact between attitudes toward helmet use and perceived importance of functional needs, but this relationship depended on the level of expressive needs, aesthetic needs, and helmet usage. The typical impact of functional needs on attitudes toward helmet use was positive (slope = .013) when all variables were at their respective means (Hypothesis 1). Hypothesis 2 tested to see if there was an impact between attitudes toward helmet use and perceived importance of expressive needs, but again, this relationship depended on the level of functional needs and helmet usage. The typical impact of expressive needs on attitudes toward helmet use was positive (slope = .014) when all variables were at their respective means. Similarly, the impact between attitudes toward helmet use and the perceived importance of aesthetic needs was dependent on the level of functional needs and helmet usage. The impact of aesthetic needs on attitudes toward helmet use was typically negative (slope = -.012) when all variables were at their respective means (Hypothesis 3). Finally, Hypothesis 4 looked at the impact between attitudes toward helmet use and the perceived importance of regulatory needs. Unlike the other three hypotheses, this relationship did not depend on any other variables. The impact of regulatory needs on attitudes toward helmet use was positive, and the strength of association was .010. Although hypothesis 1-3 were substantially supported, and hypothesis 4 was fully supported, from a statistical point of view, the interaction effects between the independent variables (i.e., FEA needs) and the covariate (i.e., helmet usage) limit the findings, so we can not really state that the hypotheses were supported. However, based on information obtained from the respondents in this study, the application of a FEAR needs assessment of snowboarding helmets could help to enhance the overall performance of snowboarders. In other words, the improvement of helmet functionality, expressive qualities, aesthetic attributes and regulatory needs would provide a more enjoyable snow activity to participants. Thus, the conceptual framework of the perceived importance of FEAR needs would be acceptable to understand the attitudes toward helmet use among snowboarders.
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    Dietary Protein Moderates Acid-Base Responses to Repeated Sprints in Exercising Horses
    Graham-Thiers, Patricia M. (Virginia Tech, 1998-11-30)
    Restricting dietary protein may reduce endogenous acid load. Horses were fed diets with 10% supplemental corn oil in experiment one and either 0% or 10% supplemental corn oil in experiment two. Also, low protein (7.5% crude protein, LP) fortified with .5% lysine and .3% threonine or high protein (14.5% crude protein, HP) was fed. Horses underwent similar interval training and standard exercise tests. In experiment two, horses performed an SET prior to conditioning. The SET consisted of warm ups at the walk and trot followed by six repeated sprints and concluding with a 30 minute recovery at the walk. All sprints were at 10 m/s except the SET prior to conditioning in experiment two, which were at 7 m/s. Blood samples were taken every two weeks and as part of SETs. Samples were analyzed for pH, pCO₂, pO2, Na⁺, K⁺, Cl⁻, lactate, total protein (TP), albumin, creatinine and plasma urea-N (PUN). Bicarbonate, strong ion difference (SID) and total weak acids (Atot) were calculated. Plasma urea-N concentrations were higher in the HP group. Plasma creatinine was not different in experiment one but was higher in the LPHF group in experiment two. Also, the LPHF group had a low body condition score and the same weight therefore had a higher lean body mass. Plasma albumin was not different in either experiment and TP was not different in experiment one. Total protein was higher in the HF groups in experiment two. Protein moderated acid-base responses to SETs in both experiments. The LP group had higher pH and bicarbonate levels as well as a tendency for a higher SID in experiment one and in the SET prior to conditioning for experiment two. Lower lactate levels were observed in the LP group in experiment one. Following conditioning in experiment two, the LP group had higher pH and bicarbonate levels but only combined with HF. Restricting dietary protein can increase pH and bicarbonate levels and high fat has been shown to improve fatty acid oxidation and spare muscle glycogen. Therefore, restricting dietary protein especially in combination with high fat may be beneficial for the exercising horse.
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    Discrimination between sincere and deceptive isokinetic knee extension response using segmental curve analysis
    Bogner, Jo-Anne Lesley Lee (Virginia Tech, 1991-01-06)
    This study intended to determine if, by using coefficients of variation derived from data collected by Fisher [1989], it would be possible to develop prediction equations to discriminate between sincere and deceptive isokinetic knee extension tests, whether these equations could be applied to a new sample, and whether prediction accuracy is dependent on test speed. Fisher [1989] trained 76 college-age males subjects to either give a true maximal response or fake an injury during an isokinetic knee extension/flexion test at 60, 180, and 300 deg/sec. Data were transmitted to a computer running Segmental Curve Analysis [Wynn, 1988; Sebolt and Earles-Price, 1989], which computed six variables for each torque curve: peak torque (PT), torque at five degrees prior to and post-PT (T-5, T+5), area to five degrees prior to PT (A-5), area beyond five degrees post-PT (A+5), and area between five degrees pre- and post-PT (A55). Coefficients of variation were computed for each variable, which were used to develop prediction equations for each speed, and for all speeds combined. The prediction equations accurately predicted condition assignments (p = 0.572 - 0.79) when applied to Fisher's [1989] data. A second sample was solicited, trained, and tested in a manner similar to Fisher [1989], and the same prediction equations were applied. There was no significant difference (p < 0.05) in the prediction accuracy of these equations between their application to Fisher's [1989] data or to data collected in the current study. Furthermore, there appeared to be no significant effect of test speed on prediction accuracy. These data suggest that coefficients of variation could be used to discriminate between sincere and deceptive isokinetic performances.
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    Does the Relative Age Effect Exist in Elite Sport? An Analysis of Olympic Competition
    Wingfield, Kathryn McGhee (Virginia Tech, 2017-06-13)
    Studies have concluded that youth sports programs have a bias selection process in identifying player talent. Athletes that are identified as talented are more likely to be born in the first three months after the eligibility cut-off for a program's particular age group. This is referred to as the relative age effect (RAE) and has been identified in many youth sports. However, it is not known if the RAE carries over into elite, adult competition. The purpose of this study was to determine if the RAE exists in Olympic competition and to compare the RAE between genders, team vs individual sports, weight class vs non-weight class sports, and medalists vs non-medalists. Data on Olympians competing in the 2012 London and 2016 Rio de Janeiro Olympics were gathered from publicly available databases. Lorenz curves were constructed and Gini coefficients calculated to detect unexpected distributions of birth months. In addition, linear regression was used to determine a directional distribution. A negative Gini coefficient and a statistically significant negative slope of the birth month distribution suggested the existence of a RAE. The results showed that there was a RAE in Olympic competition. For all athletes, the Gini coefficient was -0.0324 and the slope of -0.0014 fraction of athletes born per month. Within specific sports, the RAE varies considerably with some showing a positive RAE. Further, the RAE in Olympic athletes does not seem to be influenced by gender, type of team or success of the athlete.
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    The effect of a tryptophan-depleted diet on voluntary exercise in mice
    DeVerter, Ann M. (Virginia Tech, 1996-06-15)
    The essential amino acid tryptophan serves as the precursor to serotonin, a neurotransmitter which regulates hunger and satiety, promotes sleep, relieves depression, and is found in elevated levels following exercise. A quantitative deficit in serotonin or abnormality in its mode of action is thought to be one cause behind several psychological disorders such as depression, eating disorders, and obsessive-compulsive disorder. A decrease in dietary tryptophan has been shown to decrease serotonin production thereby, theoretically, producing the effects of a hyposerotonergic state. The purpose of this study was to further elucidate serotonin’s role in influencing an individual’s activity level by inducing a decrease in this neurotransmitter via a tryptophan-depleted diet. Specifically, 40 individually-housed mice were divided into four groups of ten. Group C received a control diet while group CW consumed a control diet and had access to a running wheel. Group E received a diet low in tryptophan while group EW was given the experimental diet and had access to a running wheel. A seven-day adaptation period was followed by a ten-day experimental period during which time groups E and EW received the experimental diet. Only the food consumption of group EW increased significantly over time. Running wheel activity was monitored every 12 hours corresponding to a light/dark cycle. An analysis of this data revealed a significant post-test rise in the activity levels of the mice in group EW compared to the activity of group CW. The wheel revolutions per 24 hours dropped by 17% in group CW while group EW’s revolutions increased by 19%. Furthermore, while revolutions increased from pre-test to post-test in only four out of 10 control subjects, they increased in all nine of the experimental subjects. It seems likely that the tryptophan depletion caused a decrease in brain serotonin levels. Therefore, the results of this experiment support the theory that the mice on a low-tryptophan diet increased their activity in a subconscious effort to normalize serotonin levels which would bring about a return of the desirable effects of this neurotransmitter.
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    The Effect of AICAR Treatment on Sarcoplasmic Reticulum Function and Possible Links to Skeletal Muscle Fatigue
    Vidt, Stacey Elizabeth (Virginia Tech, 2007-05-21)
    A compelling mystery in the study of exercise is mechanisms of skeletal muscle fatigue. Broadly described, muscle fatigue is the uncomfortable sensation that particular muscle groups are shutting down and muscle force production cannot continue. More specifically, muscle fatigue is defined as an activity-induced inability to continue to produce a desired level of force. Several groups suggest that a major cause of force loss during fatigue is reductions in the rates of sarcoplasmic reticulum (SR) calcium (Ca2+) release and uptake. These changes result in diminished contractile machinery activation, reduced force production and slowed relaxation. During exercise, adenosine 5'-triphosphate (ATP) is the energy currency that is used to support force production. As a result of ATP hydrolysis and re-synthesis, adenosine diphosphate (ADP) and adenosine monophosphate (AMP) levels rise. AMP kinase (AMPK) is an enzyme that becomes activated as a result of increased AMP levels. It is thought to function as a metabolic "master switch" within the muscle and plays a major role in carbohydrate and fat metabolism. Once AMPK is activated it regulates several ATP consuming and producing pathways. The overall objective of this project was to determine if increased metabolism during exercise contributes to SR Ca2+ dysfunction during fatigue. If this is true, artificial activation of AMPK via 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) should induce changes in SR function that are qualitatively similar to those caused by fatigue. In study 1, mice were injected with 0.85 mg/kg AICAR (or saline solution) and both gastrocnemius muscles were removed one hour later. In study 2, EDL muscles were placed in a muscle bath and incubated in AICAR (4mM) or stimulated to fatigue. Glycogen, glucose-6-phosphate (G-6-P), ATP, ADP, and phosphocreatine (PCr) were examined in all groups of muscles. Alterations in SR calcium uptake and release rates due to the presence of AICAR were also studied as a likely cause of muscle fatigue. AICAR treatment in vivo did not alter muscle glycogen, glucose, ATP, ADP or PCr concentrations. However, G-6-P levels were increased by 137%. This was accompanied by a 36% reduction in the SR Ca2+ uptake rate and a 42% reduction in Ca2+-stimulated Ca2+ ATPase activity as well as 13-15% reductions in the rates of Ca2+ release. These changes were not associated with SR Ca2+ pump content. Administration of AICAR in vitro also increased G-6-P content (200%) without altering the concentrations of glycogen, glucose, G-6-P, ATP, ADP or PCr. AICAR decreased SR Ca2+ uptake rate by 28% and the rate of Ca2+ release by 16%. For comparison, fatiguing stimulation reduced the rates of SR Ca2+ uptake and release by 31 and 41%, respectively. Taken together, these results indicate that when administered to skeletal muscle both in vivo and in vitro, AICAR evokes metabolic stress. More importantly, activation of AMPK alters skeletal muscle SR function to an extent that is qualitatively similar to that caused by fatiguing activity. At present, it is not clear how AMPK activation causes changes in SR function. However, the present finding is consistent with the notion that metabolic stress caused by exercise, affects SR function. This, in turn, leads to force loss but reduces energy demand and protects the cell from ATP depletion during maximal contractile activity.
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    Effect of Alpha-Amylase Treatment and Exercise on the Calcium Handling of the Sarcoplasmic Reticulum
    Toderico, Benjamin J. (Virginia Tech, 1999-06-16)
    The existence of a glycogen-sarcoplasmic reticulum has been demonstrated by a number of researchers. This complex is suspected to participate in the calcium uptake activities of the sarcoplasmic reticulum (SR). Removal of glycogen particles associated with this complex may alter the calcium handling abilities of the SR. This experiment sought to determine what effect exercise and treatment with a-amylase had on the abilities of the SR to regulate intracellular calcium ([Ca2+]i). Rats were either run on a treadmill for 60 min at a speed of 21 m/min and a 10% grade or were not exercised. Animals were then killed by decapitation after inhalation of CO2. Left and right gastrocnemius muscles were excised from both groups and underwent SR vesicle preparation to separate the heavy and light SR fractions (HSR and LSR respectively). Left hindlimb muscle homogenate also underwent 60 min incubation with a-amylase to digest glycogen before differential centrifugation. Treatment with a-amylase significantly depressed rate of calcium uptake by LSR and HSR fractions by 22.89% and 25.22% respectively (p<0.05). alpha-Amylase had no effect on SR's rate of calcium release. There was no effect of exercise on calcium uptake or release rates. Glycogen concentration associated with the SR was unaffected by either alpha-amylase treatment or exercise. These results indicate that treatment with alpha-amylase decreases the ability of the SR to sequester calcium ions.