• Reactive stepping strategies following lateral surface translations in individuals with a unilateral lower limb amputation

      Ferguson, Oran; Applied Health Sciences Program
      Following a loss of balance, individuals may utilize specific stepping strategies to prevent themselves from falling. The stepping strategies that are used by lower limb amputees, which likely consist of unique properties because of the limitations when using a prosthesis, have not been thoroughly identified. Therefore, this study examined the lateral reactive stepping strategies used eight amputees and ten non-amputees. They experienced four support-surface translations in both the leftward and rightward direction. Results indicated that amputees use unique reactive stepping strategies, particularly with the unloaded leg and when the direction of the perturbation causes unloading of the prosthesis. Amputee stepping strategies were characterized by fewer steps, lower quality of balance recovery, and wider variety compared to non-amputees. This study's findings highlight the reliance on the hip strategy in amputee reactive balance, and future studies should explore how amputees use their hip and trunk while executing reactive stepping strategies.
    • Redefining Exhaustion: Considerations for the Modeling of Critical Power

      Steele, Scott; Applied Health Sciences Program
      Background: The relationship between exercise intensity and the limit of tolerance is the focus of the Critical Power (CP) model. CP defines the upper limit for which exercise is steady state and is – in theory – indefinitely sustainable. However, this limit of tolerance at CP is often well below 30 min. Purpose: We want to test the hypothesis that 1) a clinically significant residual W’ capacity (W’res) does exist, 2) that the size of W’res is inversely related to tlim used in the testing protocols, and 3) that accounting for W’res will result in an improved calculation of the Critical Power (CP), as determined by an increased time to exhaustion at CP. Methods: Nine well-trained cyclists performed a ramp test and four high-intensity tests to exhaustion on a cycle ergometer to determine CP and the curvature constant (W’). Two tests to exhaustion were then performed at the traditional CP (CPtrad) and a novel, modified CP (CPmod) to test the practical significance of the residual capacity on the calculation of the CP. Results: All participants were able to perform work above CP even after reaching the limit of tolerance, despite no significant changes in physiological parameters. Including the W’res resulted in significantly lower estimations of CP (TRAD: 281W, MOD: 278 W; p = 0.015) and higher estimations of W’ (TRAD: 15.8 kJ, MOD: 17.8 kJ; p = 0.008). Significance: Athletes were able to continue generating power above CP, even after reaching the limit of tolerance. This residual capacity resulted in a significantly lower estimate of CP and significantly higher estimation of W’.
    • Reduced power output in skeletal muscles devoid of skMLCK: RLC phosphorylation contributes to peak performance

      Bowslaugh, Joshua; Applied Health Sciences Program
      Regulatory light chain (RLC) phosphorylation in fast twitch muscle is catalyzed by skeletal myosin light chain kinase (skMLCK), a reaction known to increase muscle force, work, and power. The purpose of this study was to explore the contribution of RLC phosphorylation on the power of mouse fast muscle during high frequency (100 Hz) concentric contractions. To determine peak power shortening ramps (1.05 to 0.90 Lo) were applied to Wildtype (WT) and skMLCK knockout (skMLCK-/-) EDL muscles at a range of shortening velocities between 0.05-0.65 of maximal shortening velocity (Vmax), before and after a conditioning stimulus (CS). As a result, mean power was increased to 1.28 ± 0.05 and 1.11 ± .05 of pre-CS values, when collapsed for shortening velocity in WT and skMLCK-/-, respectively (n = 10). In addition, fitting each data set to a second order polynomial revealed that WT mice had significantly higher peak power output (27.67 ± 1.12 W/ kg-1) than skMLCK-/- (25.97 ± 1.02 W/ kg-1), (p < .05). No significant differences in optimal velocity for peak power were found between conditions and genotypes (p > .05). Analysis with Urea Glycerol PAGE determined that RLC phosphate content had been elevated in WT muscles from 8 to 63 % while minimal changes were observed in skMLCK-/- muscles: 3 and 8 %, respectively. Therefore, the lack of stimulation induced increase in RLC phosphate content resulted in a ~40 % smaller enhancement of mean power in skMLCK-/-. The increase in power output in WT mice suggests that RLC phosphorylation is a major potentiating component required for achieving peak muscle performance during brief high frequency concentric contractions.
    • Regulation of Protein Turnover during Hyper-osmotic Stress in Skeletal Muscle

      Vandommele, Cody; Applied Health Sciences Program (Brock University, 2013-02-12)
      The purpose of this study was to examine the effect of hyper-osmotic stress on protein turnover in skeletal muscle tissue using an established in-vitro model. Rat EDL muscles were incubated in either hyper-osmotic (400 ± 10 Osm) or isoosmotic (290 ± 10 Osm) custom-modified media (Gibco). L-[14C]-U-phenylalanine (n=8) and cycloheximide (n=8) were used to quantify protein synthesis and degradation, respectively. Western blotting analyses was performed to determine the activation of protein synthesis and degradation pathways. During hyperosmotic stress, protein degradation increased (p<0.05), while protein synthesis was decreased (p<0.05) as compared to the iso-osmotic condition. The decline in protein synthesis was accompanied by a decrease (p<0.05) in p70s6 kinase phosphorylation, while the increase in protein degradation was associated with an increase (p<0.05) in autolyzed calpain. Therefore, hyper-osmotic extracellular stress results in an intracellular catabolic environment in mammalian skeletal muscle tissue.
    • Relationship between adverse childhood experiences and arterial stiffness over time from childhood into early adulthood

      Rafiq, Talha; Applied Health Sciences Program
      It is well established in the literature that there is an association among adults between adverse childhood experiences (ACEs) and arterial stiffness, and between arterial stiffness and cardiovascular disease. However, recent cross-sectional evidence suggests that ACEs may play an important role in the development and progression of arterial stiffness, but it remains unclear when these changes begin to manifest. Therefore, the purpose of this research was to examine the relationship between ACEs and arterial stiffness from childhood into adulthood using population-based longitudinal data. A total of 76 young adults (females = 44), with an average age of 21 years (SD = 1) were included in this study. Overall, a total of 71 respondents reported to have experienced at least one ACE. The findings of this study showed ACEs-exposed individuals have a greater increase in arterial stiffness over time from childhood into young adulthood. This increase was similar for both males and females. Also, differences in heart rate, systolic blood pressure, body mass index, and physical activity did not mediate the relationship between ACEs and arterial stiffness over time. It is therefore important to recognize individuals with exposure to ACEs early on in life in an effort to lower the risk of arterial stiffness and in turn the cascade of events leading to cardiovascular disease.
    • The relationship between adverse childhood experiences and pro-inflammatory analytes and the mediating role of cortisol

      Wong, Kingston; Applied Health Sciences Program
      Adverse childhood experiences (ACEs) are harmful experiences that have occurred during the developing years of life. ACEs often include maltreatment, household dysfunctions and other traumatic events. People with ACEs have been found to be at greater risk of pulmonary, cardiovascular and auto-immune diseases. Recent research has suggested that the epigenetic regulation occurring as a result of these ACEs can program macrophages to sustain inflammatory processes and therefore contribute to the development of these diseases. As one of the primary responders to stress, cortisol is also a suppressor of inflammation. Therefore, dysregulation of the cortisol levels, chronically high or low, also brought forth by ACEs exposure can affect inflammation. The purpose of the current study was to investigate the relationship between ACEs exposure and physiological measures including cortisol and different pro-inflammatory analytes. This cross-sectional study included follow-up data from 156 participants as part of the Niagara Longitudinal Heart Study. Out of the 156 participants, a final sample of 101, with 23 males and 78 females, complete with physiological measures was included in the analyses. The current study collected ACEs data from questionnaire, cortisol from hair, and inflammatory analytes including CRP, IL-6Rα, gp130, sTNFr1, sTNFr2, IFN-γ, and IL-10 from blood. Total ACEs score was negatively associated with cortisol levels. Every additional exposure to a type of ACEs decreased cortisol levels by 21.2 (pg/mg) on average. Exposure to ACEs was positively associated with IL-6Rα but was not associated with all other inflammatory analytes. Every additional exposure to a type of ACEs increased IL-6Rα levels by 284.6 (pg/mL) on average. In contrast to previous literature, sex differences from the regression analyses were also found in the current study among the inflammatory analytes CRP, IL-6Rα, sTNFr1, and IL-10. Cortisol did not mediate the relationship between exposure to ACEs and the different inflammatory analytes. The current study was limited in properly detecting associations as the pilot sample was underpowered. The proportion of cortisol availability in males was much lower than in females. The current study found that ACEs were associated with lowered chronic cortisol and elevated IL-6Rα.
    • The relationship between body mass index and breast cancer recurrence/progression and breast cancer-specific death

      Tosevski, Cedomir; Applied Health Sciences Program (Brock University, 2011-03-08)
      The aim of this study was to describe the nonlinear association between body mass index (BMI) and breast cancer outcomes and to determine whether BMI improves prediction of outcomes. A cohort of906 breast cancer patients diagnosed at Henry Ford Health System, Detroit (1985-1990) were studied. The median follow-up was 10 years. Multivariate logistic regression was used to model breast cancer recurrence/progression and breast cancer-specific death. Restricted cubic splines were used to model nonlinear effects. Receiver operator characteristic areas under the curves (ROC AUC) were used to evaluate prediction. BMI was nonlinearly associated with recurrence/progression and death (p= 0.0230 and 0.0101). Probability of outcomes increased with increase or decrease ofBMI away from 25. BMI splines were suggestive of improved prediction of death. The ROC AUCs for nested models with and without BMI were 0.8424 and 0.8331 (p= 0.08). I f causally associated, modifying patients BMI towards 25 may improve outcomes.
    • Relationship between physical activity and resting secretory immunity in children

      Cieslak, Thomas J.; Applied Health Sciences Program (Brock University, 2002-05-21)
      This study examined relationships among physical activity, body fat and salivary immonoglobulin A (sIgA) levels in adolescent children of Southern Ontario. Gender differences on these factors were also assessed. Sixty-one grade-five students (10-1 lyrs), males (n=29) and females (n=31), who had not received a flu vaccination in the past 12 months, participated in the study. They were assessed for: aerobic power (20-m shuttle run), relative body fat (bioelectrical impedance analysis), sIgA, sIgA/albumin ratio, and salivary Cortisol. Each subject completed the Habitual Activity Estimation Scale and the Participation Questioimaire. Students wore a pedometer for 48h to estimate their average total distance traveled per day. The results show 40% of the children were over 25% body fat and 50% of them spend less than five hours per day in any physical activities. Salivary IgA was not related to salivary Cortisol, physical activity, fitness level or body fat in this age group. There were no gender differences in sIgA and Cortisol levels. Boys had a significantly higher aerobic power and daily distance traveled, but reported similar organized and fi-ee time activity participation levels as the girls. The test-retest reproducibility for salivary Cortisol was 0.663 (p<0.01), while long term sIgA and sIgA/albumin ratio reproducibility was non-significant for repeated measurements taken after six weeks. It was found that salivary IgA has not been shovm to be a stable measure in children, in contrast to the results found in the literatiu-e that tested adults and the relationship with physical activity, fitness level and body fat.
    • Relationship between Socio-Demographic Factors and Familial and Partner Pressures to Conceive in HIV-Positive Women in Ontario

      Mehta, Sachin; Applied Health Sciences Program (Brock University, 2014-07-28)
      This study examined the relationship between socio-demographic factors and family and partner pressure to conceive in women living with HIV in Ontario, Canada. A total of 490 women, aged 18-52 years were included in the study. The HIV Pregnancy Planning Questionnaire was used to collect data on socio-demographic, medical, and pressure variables. Multivariate logistic regression analysis suggest that increased age, years lived in Canada, and living in Toronto were associated with lower odds, and being married and having 0-1 lifetime births were associated with higher odds of family pressure to conceive. Increased age was associated with lower odds, and being married and living in Toronto were associated with higher odds of partner pressure to conceive. Findings suggest that socio-demographic factors influence the fertility decision-making process. Health care providers should consider socio-demographic factors along with medical factors when assisting women living with HIV and their partners to make informed reproductive decisions.
    • The relationship between socioeconomic status, schools and bone health among adolescent females in Southern Ontario

      Imam, Sabrina; Applied Health Sciences Program (Brock University, 2013-09-11)
      We studied the association between socioeconomic status (SES), school attended and bone health measured by bone speed of sound (SOS) among adolescent females in Canada. 412 participants from six randomly selected schools in Southern Ontario were examined. Bone SOS was measured by quantitative ultrasound. Participant’s school and aggregate area-based census-derived (AABCD) SES were evaluated as predictors. Mean participant age was 15.7 (SD 1.0) years. Average median family income was $68,162 (SD $19,366). Median family income was non-linearly associated with bone SOS and restricted cubic splines described the relationship. Univariate regression, accounting for clustering of participants in schools, revealed a significant non-linear association between AABCD-median family income and non-dominant tibial SOS (LRT p = 0.031). Multivariable regression revealed school to have a significant impact (LRT p = 0.0001). High schools had a strong influence on the bone health of female students and this effect overrode the effect of SES.
    • Relationship between Surface and Indwelling EMG Spike Shape Measures

      Parro, Justin; Applied Health Sciences Program (Brock University, 2014-09-04)
      Indwelling electromyography (EMG) has great diagnostic value but its invasive and often painful characteristics make it inappropriate for monitoring human movement. Spike shape analysis of the surface electromyographic signal responds to the call for non-invasive EMG measures for monitoring human movement and detecting neuromuscular disorders. The present study analyzed the relationship between surface and indwelling EMG interference patterns. Twenty four males and twenty four females performed three isometric dorsiflexion contractions at five force levels from 20% to maximal force. The amplitude measures increased differently between electrode types, attributed to the electrode sensitivity. The frequency measures were different between traditional and spike shape measures due to different noise rejection criteria. These measures were also different between surface and indwelling EMG due to the low-pass tissue filtering effect. The spike shape measures, thought to collectively function as a means to differentiate between motor unit characteristics, changed independent of one another.
    • The Relative Age Effect in Minor Ice Hockey: Investigating the 'Underdog Effect'

      Belgiorgio, Matthew; Applied Health Sciences Program (Brock University, 2014-09-05)
      Abstract The Relative Age Effect (RAE), defined as a skewed birth date distribution, has been identified as a known phenomenon in minor ice hockey. The purpose of this study was to investigate the relationship between the RAE, physical measurements, and skating ability/in-game performance in forty-four youth male ice hockey players competing in the same age cohort. Physical anthropometrics, grip strength, in-game performance and skating abilities were measured. An RAE was found in the sample (χ2(3, N = 44) = 12.18, p = 0.007). Players born in the first half of the age cohort had longer leg length (F(1,42) =4.49 , p = 0.04), larger body mass (F(1,42) = 3.90, p = 0.05), and stronger grip strength (F(1,42) = 7.58, p = 0.009). Performance scores were negatively associated with grip strength (r = -.443, p = 0.003). Findings suggest that adequate skill development can help relatively younger players overcome physical maturity disadvantages.
    • Relative importance of body composition, osteoporosis- related behaviours and socioeconomic status on bone SOS in adolescent females

      Holmes, Brianna Lynn.; Applied Health Sciences Program (Brock University, 2009-02-16)
      The purpose of this study was to examine the associations between bone speed of sound (SOS) and body composition, osteoporosis-related health behaviours, and socioeconomic status (SES) in adolescent females. A total of 442 adolescent females in grades 9-11 participated. Anthropometric measures of height, body mass, and percent body fat were taken, and osteo-protective behaviours such as oral contraceptive use (OC), physical activity and daily calcium intake were evaluated using self-report questionnaires. Bone SOS was measured by transaxial quantitative ultrasound (QUS) at the distal radius and mid-tibia. The results suggest that fat mass is a significant negative predictor of tibial SOS, while lean mass is positively associated with radial SOS scores and calcium intake was positively associated with tibial SOS scores (p<O.05). Additionally, users of OC had higher radial SOS. No significant correlation was found between physical activity and bone SOS. Therefore bone strength measured by QUS is reduced in adolescents with an increased fat mass, and influenced positively by OC use, calcium intake and lean mass.
    • Reliability Generalization: Exploring Score Reliability Variance with Ryff’s Scale of Psychological Well-Being

      Crouch, Meghan; Applied Health Sciences Program
      The purpose of this study was to conduct a Reliability Generalization (RG; Vacha-Haase, 1998) for Ryff’s Scale of Psychological Well-Being (PWB; Ryff, 1989) to characterize the average score reliability, the variability of the score reliability, and explore possible sample and test characteristics that influenced score reliability across studies. Studies were included in the current investigation if they had been published in a peer-reviewed journal, used one or more subscales of the Ryff’s PWB, estimated coefficient alpha value(s) for the PWB subscale(s) used, and were written in English. Out of the 924 articles generated by the search strategy, a total of 264 articles were included in the final sample for meta-analysis. The average coefficient alpha for the composite PWB scale was 0.858, with mean coefficient alphas ranging from 0.722 for the Autonomy subscale to 0.801 for the Self-Acceptance subscale. Statistically significant heterogeneity was present across all mean coefficient alphas (p < .05), with the heterogeneity index above 95% for both composite and subscale alphas. Consequently, select sample and test characteristics of the primary studies were explored as possible moderator variables on coefficient alpha estimates, with significant differences in score reliability estimates across select demographic and test characteristics. Test length accounted for the majority of variance among alpha coefficients with R2 values ranging from 40% on the Environmental Mastery subscale to 71% on the Self-Acceptance subscales across the primary studies. In light of the current findings, implications for researchers using Ryff’s PWB including informed score reliability reporting practices are discussed.
    • Reliability of a new measure of motoneuron excitability

      Christie, Anita.; Applied Health Sciences Program (Brock University, 2003-07-09)
      Objectlve:--This study examined the intraclass reliability· of different measures of the excitability of the Hoffmann reflex, derived from stimulus-response curves. The slope of the regression line of the H-reflex stimulus-response curve advocated by Funase et al. (1994) was also compared to the peak of the first derivative of the H-reflex stimulus-response curve (dHIdVmax), a new measure introduced in this investigation. A secondary purpose was to explore the possibility of mood as a covariate when measuring excitability of the H-reflex arc. Methods: The H-reflex amplitude at a stimulus intensity corresponding to 5% of the maximum M-wave (Mmax) is an established measure that was used as an additional basis of comparison. The H-reflex was elicited in the soleus for 24 subjects (12 males and 12 females) on five separate days. Vibration was applied to the Achilles tendon prior to stimulation to test the sensitivity of the measures on test day four. The means of five evoked potentials at each gradually increasing intensity, from below H-reflex threshold to above Mmax, were used to create both the H-reflex and M-wave stimulus response curves for each subject across test days. The mood of the subjects was assessed using the Subjective Exercise Experience Scale (SEES) prior to the stimulation protocol each day. Results: There was a modest decrease in all H-reflex measures from the first to third test day, but it was non-significant (P's>0.05). All measures of the H-reflex exhibited a profound reduction following vibration on test day four, and then returned to baseline levels on test day five (P's<0.05). The intraclass correlation coefficient (ICC) for H-reflex amplitude at 5% of Mmax was 0.85. The ICC for the slope of the regression line was 0.79 while it was 0.89 for dH/dVmax. Maximum M-wave amplitude had an ICC of 0.96 attesting to careful methodological controls. The SEES subscales of fatigue and psychological well-being remained unchanged IV across the five days. The psychological distress subscale (P<O.05), as well as the amplitude of the H-reflex_.at5% Mmax·(P<O.OI) showed a significant cubic trend across the live days. No significant correlation was found between Hs% and psychological distress (P>O.05). Conclusions: The peak of the first derivative of the H-reflex stimulus-response curve (dH/dVmax) was shown to have comparable reliability and sensitivity to other more established measures of excitability. Psychological distress and the amplitude of the H-reflex at 5% Mmax follow similar trends across days, however there was no significant correlation between the two measures. Significance: The proposed method appears to be a more robust measure ofH-reflex excitability than the other methods tested. As such it would be an advantageous method to apply in clinical and investigative settings. Additionally, the results suggest that the relationship between psychological distress and H-reflex amplitude should be investigated further.
    • The reliability of an isometric test based on constant perception of effort

      Kilburn, Shane Michael.; Applied Health Sciences Program (Brock University, 2009-02-16)
      To date there is no documented procedure to extrapolate findings of an isometric nature to a whole body performance setting. The purpose of this study was to quantify the reliability of perceived exertion to control neuromuscular output during an isometric contraction. 21 varsity athletes completed a maximal voluntary contraction and a 2 min constant force contraction at both the start and end of the study. Between pre and post testing all participants completed a 2 min constant perceived exertion contraction once a day for 4 days. Intra-class correlation coefficient (R=O.949) and standard error of measurement (SEM=5.12 Nm) concluded that the isometric contraction was reliable. Limits of agreement demonstrated only moderate initial reliability, yet with smaller limits towards the end of 4 training sessions. In conclusion, athlete's na"ive to a constant effort isometric contraction will produce reliable and acceptably stable results after 1 familiarization sessions has been completed.
    • Reliability of muscle fiber conduction velocity in the tibialis anterior

      McIntosh, Kyle; Applied Health Sciences Program (2012-07-04)
      This document could not have been completed without the hard work of a number of individuals. First and foremost, my supervisor, Dr. David Gabriel deserves the utmost recognition for the immense effort and time spent guiding the production of this document through the various stages of completion. Also, aiding in the data collection, technical support, and general thought processing were Lab Technician Greig Inglis and fellow members of the Electromyographic Kinesiology Laboratory Jon Howard, Sean Lenhardt, Lara Robbins, and Corrine Davies-Schinkel. The input of Drs. Ted Clancy, Phil Sullivan and external examiner Dr. Anita Christie, all members ofthe assessment committee, was incredibly important and vital to the completion of this work. Their expertise provided a strong source of knowledge and went to ensure that this project was completed at exemplary level. There were a number of other individuals who were an immense help in getting this project off the ground and completed. The donation of their time and efforts was very generous and much needed in order to fulfill the requirements needed for completion of this study. Finally, I cannot exclude the contributions of my family throughout this project especially that of my parents whose support never wavers.
    • Risk Factors for Soil-transmitted Helminth Infections in Schoolchildren from Rural Communities in Honduras

      Gabrie, José; Applied Health Sciences Program (Brock University, 2013-08-22)
      Background: Honduras is endemic for soil-transmitted helminth (STH) infections. However, knowledge gaps remain in terms of risk factors involved in STH transmission and infection intensity. Objectives: To determine the prevalence and intensity of STH infections in schoolchildren living in rural Honduras. Additionally, to investigate risk factors associated with STH infections. Methods: A cross-sectional study was done among Honduran rural schoolchildren, in 2011. Demographic and epidemiological data were obtained and STH infections were determined using Kato-Katz method. Results: A total of 320 children completed the study. Overall and specific prevalences for Ascaris lumbricoides, Trichuris trichiura and hookworms were 72.5%, 30%, 67% and 16%, respectively. Several risk factors associated with STH transmission and infection intensity were identified at the individual and familial level as well as at the schools. Conclusions: Improving hygienic conditions and providing semi-annual deworming treatment are feasible interventions that could enhance undergoing STH control activities.
    • Role of acute exercise-induced brain-derived neurotrophic factor on beta-site amyloid precursor protein cleaving enzyme 1 and amyloid precursor protein processing in the brain

      Baranowski, Bradley John; Applied Health Sciences Program
      Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the rate limiting enzyme in the pathway responsible for beta-amyloid production, a pathological feature of Alzheimer’s Disease (AD). Exercise has been shown to reduce BACE1 activity, although the mechanisms responsible are unknown. Exercise has also been shown to increase brain-derived neurotrophic factor (BDNF) content and signalling, however whether this neurotrophic factor mediates the effects of exercise on BACE1 regulation requires further investigation. C57BL/6J male mice were placed on a low (LFD) or high fat diet (HFD) for 10-weeks. Following the intervention, the mice either remained sedentary or underwent an acute bout of treadmill running. Mice were euthanized and the prefrontal cortex and hippocampus were collected for analysis. The remaining sedentary mice (n=24) were used for an explant experiment where the tissue was directly treated with BDNF. The HFD reduced BDNF content in the hippocampus, however, an acute bout of exercise was able to significantly increase BDNF content in the prefrontal cortex. We further demonstrated that direct treatment with BDNF results in reductions in BACE1 activity in the prefrontal cortex. This novel finding demonstrates that BDNF can reduce BACE1 activity, independent of an exercise stimulus. Moreover, this finding shows for the first time, that there is a direct link between BDNF signalling and BACE1 regulation in this region of the brain. This highlights the viability of using exercise and BDNF to modulate BACE1 activity as a potential therapeutic intervention, without the negative consequences of drug-induced inhibitions.
    • The Role of Dopamine on Central Neuromuscular Activation during Passive Hyperthermia

      Scholey, Aiden; Applied Health Sciences Program
      Acute methylphenidate (MPH) (dopamine reuptake inhibitor) ingestion improves cycling time trial performance and power output in hot conditions (30 C), while also allowing for tolerance of higher core temperatures. However, the mechanisms for why this occurs have not been isolated. One potential explanation for this ergogenic benefit is that MPH intake was enhancing neuromuscular activation. Thus, this research project examined the influence of MPH on neuromuscular activation during hyperthermia. Participants ingested either placebo (PLA; 20mg) or MPH (Ritalin; 20mg) 1 hour prior to a passive heating protocol. 6 participants were passively heated until volitional cessation, or after 3 hours of heating had passed. Neuromuscular responses, as indicated by maximal voluntary contraction (MVC) force, and voluntary activation (VA) percentage were assessed prior to drug ingestion, 1 hour after MPH wash-in, throughout the heating protocol and at cessation of heating. A primary non-significant finding of this research project was that participants reached higher rectal temperatures (Tre) by ~0.3 C in trials where they ingested MPH (p = 0.065). This effect occurred in absence of any differences in thermal comfort or sensation ratings or heating durations. However, while MPH improves thermal tolerance, it was not able to attenuate the decreases in MVC force and VA that occurred during passive heating. Therefore, the aforementioned ergogenic benefits that MPH has in hot conditions are not occurring as a result of enhanced neuromuscular activation.