Commercially Available Capsaicin Supplement Fails to Enhance Time-to-Exhaustion During Cycling

International Journal of Exercise Science 13(2): 225-233, 2020. This study examined whether a commercially available low-dose (1.2 mg), chewable capsaicin supplement could enhance endurance cycling performance. Thirteen young (8M/5F), recreationally active individuals (age = 24.2 ± 2.9 yrs, body fat = 21.2 ± 6.1%) participated in the study. The study consisted of three visits, beginning with an initial evaluation of cardiorespiratory fitness (37.1 ± 5.5 ml/kg/min). During the second and third study visits, participants completed time-to-exhaustion (TTE) tests on a cycle ergometer at a workload eliciting ~90% VO2max, 45 minutes after ingesting either a 139 kcal capsaicin fruit gummy, or eucaloric placebo. Heart rate and rating of perceived exertion (RPE) were recorded every two minutes throughout the TTE sessions. Time-to-exhaustion was not significantly different (p\u3e 0.05; d= 0.13) between placebo (487.8 ± 187.7 sec) and capsaicin (517.5 ± 258.4 sec) trials. Furthermore, heart rate responses and ratings of perceived exertion were similar (p\u3e 0.05) between trials. These findings suggest that pre-exercise ingestion of a commercially available low-dose (1.2 mg), chewable capsaicin supplement fails to provide ergogenic benefits for time-to-exhaustion during cycling exercise. Higher doses may be necessary to elicit the performance-enhancing benefits observed during alternative exercise modalities (i.e., running) of comparable intensity

Single Muscle Fibre Contractile Function With Ageing

Ageing is accompanied by decrements in the size and function of skeletal muscle that compromise independence and quality of life in older adults. Developing therapeutic strategies to ameliorate these changes is critical but requires an in-depth mechanistic understanding of the underlying physiology. Over the past 25 years, studies on the contractile mechanics of isolated human muscle fibres have been instrumental in facilitating our understanding of the cellular mechanisms contributing to age-related skeletal muscle dysfunction. The purpose of this review is to characterize the changes that occur in single muscle fibre size and contractile function with ageing and identify key areas for future research. Surprisingly, most studies observe that the size and contractile function of fibres expressing slow myosin heavy chain (MHC) I are well-preserved with ageing. In contrast, there are profound age-related decrements in the size and contractile function of the fibres expressing the MHC II isoforms. Notably, lifelong aerobic exercise training is unable to prevent most of the decrements in fast fibre contractile function, which have been implicated as a primary mechanism for the age-related loss in whole-muscle power output. These findings reveal a critical need to investigate the effectiveness of other nutritional, pharmaceutical or exercise strategies, such as lifelong resistance training, to preserve fast fibre size and function with ageing. Moreover, integrating single fibre contractile mechanics with the molecular profile and other parameters important to contractile function (e.g. phosphorylation of regulatory proteins, innervation status, mitochondrial function, fibre economy) is necessary to comprehensively understand the ageing skeletal muscle phenotype

Effect of a Commercially Available Low-Dose Capsaicin Supplement on Knee Extensor Contractile Function

International Journal of Exercise Science 13(2): 312-318, 2020. Capsaicin, the active pungent ingredient in chili peppers and various spicy foods, is demonstrated to influence a variety of physiological systems including skeletal muscle. The purpose of this study was to examine if a chewable capsaicin supplement (1.2 mg) could enhance isokinetic knee extensor contractile performance. Nine young, recreationally active individuals (5 females/4 males; 23.6 ± 1.5 yrs; 24.2 ± 3.3 kg/m2) participated in this randomized, single-blind crossover study. Following a familiarization session, participants completed two isokinetic knee extensor contractile function assessments, 45 minutes after ingesting either a capsaicin fruit gummy or eucaloric placebo, the order of which was randomized. Knee extensor peak torque (strength), summed torque (endurance) and fatigue index (fatigue) were compared between trials. Knee extensor peak torque was significantly greater (p \u3c 0.05; d= 0.80) in the capsaicin (126.0 ± 40.4 N⋅m-1) than the placebo (118.8 ± 41.3 N⋅m-1) trial. No significant differences (p \u3e 0.05) were found for summed torque (8012 ± 2771 vs. 7823 ± 2611 N⋅m-1; d= 0.45) or fatigue index (56.0 ± 17.1 vs. 48.7 ± 21.0 %; d= 0.46) between capsaicin and placebo trials, respectively. These findings, in a relatively modest and mixed-gender sample, suggest that pre-exercise capsaicin ingestion may benefit knee extensor muscle strength but does not appear to affect parameters of skeletal muscle endurance or fatigue

Predictors of Performance during a 161 km Mountain Footrace

Training volume and cardiovascular dynamics influence endurance performance. However, there is limited information on the interplay between training volume, cardiovascular dynamics, and performance in ultra-marathon athletes. PURPOSE: We aimed to determine predictors of performance in finishers of the 2023 Western States Endurance Run (WSER). METHODS: Sixty participants who finished the race (49 males/11 females; mean age: 44.7 ± 9.6 y, range: 26–66 y; BMI: 22.7 ± 2.2 kg/m2) completed pre-race surveys including average training volume (AV) and peak training volume (PV), as well as resting cardiovascular measures including resting heart rate (RHR) and augmentation index (AIx), a measure of wave reflection characteristics. Based on WSER completion time, we calculated average running velocity (RV). We assessed associations among 22 variables using bivariate correlation analysis (Pearson’s Correlation for normally distributed data and Spearman’s Rank Correlation if normality was not met). Within our listed variables, normality was met in age and AV. Additionally, we completed multiple regression analyses for predictors. We present descriptive data as mean ± SD. RESULTS: Participants had an average RV of 6.33 ± 0.97 km/h (3.93 ± 0.6 mph), and reported an AV of 91.9 ± 24.5 km/wk (57.1 ± 15.2 miles/wk) and a PV of 141.0 ± 47.2 km/wk (87.6 ± 29.3 miles/wk). We observed significant associations between RV and age (r(58) = -0.57, p r(58) = 0.41, p r(58) = 0.34, p R2 = 0.37; F(3,56) = 12.4, pb1 = 0.013; t(56) = 2.57, p = 0.013), resulting in a 0.33 km/h increase in RV for every 25-km increase in AV. Last, significant relations existed between RV and AIx (r(58) = -0.30, p = 0.022); and RHR (r(58) = -0.26, p = 0.046). CONCLUSION: We found that (1) average weekly training volume is a significant predictor of performance in elite ultra-marathon athletes and (2) race performance was inversely associated with resting arterial wave reflection characteristics and heart rate

Exercise and Nutritional Interventions to Combat Fatigue: From Athletes to Aging

Presentation given at Muscle Physiology Lecture Series

Cardiac-Autonomic and Hemodynamic Responses to a Hypertonic, Sugar-Sweetened Sports Beverage in Physically Active Men

Hydration practices may confound heart rate variability (HRV) measurements when collected in the pre-training period. We aimed to determine the effects of ingesting a hypertonic, sugar-sweetened sports beverage on HRV and hemodynamic parameters in physically active young men. Fifteen subjects consumed 591 ml of Gatorade (6% carbohydrate, ~330 mOsmol/kg), 591 ml water, or 10 ml water (control) in random order on separate days following overnight fasting. HRV and hemodynamics were evaluated in 5-min windows immediately before (T1) and 5-10 min (T2), 25-30 min (T3), 40-45 min (T4), and 55-60 min (T5) post-drinking. Root-mean square of successive differences and the standard deviation of normal RR intervals increased post-water intake at all time-points relative to T1 (PThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Evidence for the Contribution of Gut Microbiota to Age-Related Anabolic Resistance

Globally, people 65 years of age and older are the fastest growing segment of the population. Physiological manifestations of the aging process include undesirable changes in body composition, declines in cardiorespiratory fitness, and reductions in skeletal muscle size and function (i.e., sarcopenia) that are independently associated with mortality. Decrements in muscle protein synthetic responses to anabolic stimuli (i.e., anabolic resistance), such as protein feeding or physical activity, are highly characteristic of the aging skeletal muscle phenotype and play a fundamental role in the development of sarcopenia. A more definitive understanding of the mechanisms underlying this age-associated reduction in anabolic responsiveness will help to guide promyogenic and function promoting therapies. Recent studies have provided evidence in support of a bidirectional gut-muscle axis with implications for aging muscle health. This review will examine how age-related changes in gut microbiota composition may impact anabolic response to protein feeding through adverse changes in protein digestion and amino acid absorption, circulating amino acid availability, anabolic hormone production and responsiveness, and intramuscular anabolic signaling. We conclude by reviewing literature describing lifestyle habits suspected to contribute to age-related changes in the microbiome with the goal of identifying evidence-informed strategies to preserve microbial homeostasis, anabolic sensitivity, and skeletal muscle with advancing age

Effect of Acute Low-Dose Capsaicin Supplementation on Skeletal Muscle Contractile Function

Presentation given at the Georgia Southern Armstrong Student Symposium, Savannah, GA