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Dietary Supplements for Athletic Performance in Women: Beta-Alanine, Caffeine, and Nitrate

Molly J. Murphy, Blake R. Rushing, Susan J. Sumner, and Anthony C. Hackney

Beta-alanine, caffeine, and nitrate are dietary supplements generally recognized by the sport and exercise science community as evidence-based ergogenic performance aids. Evidence supporting the efficacy of these supplements, however, is greatly skewed due to research being conducted primarily in men. The physiological differences between men and women, most notably in sex hormones and menstrual cycle fluctuations, make generalizing male data to the female athlete inappropriate, and potentially harmful to women. This narrative review outlines the studies conducted in women regarding the efficacy of beta-alanine, caffeine, and nitrate supplementation for performance enhancement. Only nine studies on beta-alanine, 15 on caffeine, and 10 on nitrate in healthy women under the age of 40 years conducted in normoxia conditions were identified as relevant to this research question. Evidence suggests that beta-alanine may lower the rate of perceived exertion and extend training bouts in women, leading to greater functional adaptations. Studies of caffeine in women suggest the physiological responder status and caffeine habituation may contribute to caffeine’s efficacy, with a potential plateau in the dose–response relationship of performance enhancement. Nitrate appears to vary in influence based on activity type and primary muscle group examined. However, the results summarized in the limited literature for each of these three supplements provide no consensus on dosage, timing, or efficacy for women. Furthermore, the literature lacks considerations for hormonal status and its role in metabolism. This gap in sex-based knowledge necessitates further research on these ergogenic supplements in women with greater considerations for the effects of hormonal status.

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Erratum: Hurst, Saunders, & Coleman (2020)

James A. Betts

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Methodology Review: A Protocol to Audit the Representation of Female Athletes in Sports Science and Sports Medicine Research

Ella S. Smith, Alannah K.A. McKay, Kathryn E. Ackerman, Rachel Harris, Kirsty J. Elliott-Sale, Trent Stellingwerff, and Louise M. Burke

Female-specific research on sports science and sports medicine (SSSM) fails to mirror the increase in participation and popularity of women’s sport. Females have historically been excluded from SSSM research, particularly because their physiological intricacy necessitates more complex study designs, longer research times, and additional costs. Consequently, most SSSM practices are based on research with men, despite potential problems in translation to females due to sexual dimorphism in biological and phenotypical parameters as well as differences in event characteristics (e.g., race distances/durations). Recognition that erroneous extrapolations may hamper the efforts of females to maximize their athletic potential has created an impetus to acknowledge and readdress the sex disparity in SSSM research. To direct the priorities for future research, it is prudent to first develop a comprehensive understanding of the gaps in current knowledge by systematically “auditing” the literature. By conducting audits of the literature to highlight underdeveloped topics or identify potential problems with the quality of research, this information can then be used to expediently direct new research activities. This paper therefore presents a standardized audit methodology to establish the representation of female athletes in subdisciplines of existing SSSM research, including a template for reporting the results of key metrics. This standardized audit process will enable comparisons over time and between research subdisciplines. This working guide provides an important step toward achieving sex equity across SSSM research, with the eventual goal of providing evidence-based recommendations specific to the female athlete.

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Repeated-Sprint Exercise in the Heat Increases Indirect Markers of Gastrointestinal Damage in Well-Trained Team-Sport Athletes

Alice Wallett, Andrew McKune, David Pyne, David Bishop, Olivier Girard, Philo Saunders, and Julien Périard

Introduction: Athletes engaged in repeated-sprint training in the heat can be at an increased risk of gastrointestinal ischemia and damage in response to a redistribution of blood to working skeletal muscles and the skin. This study investigated the effects of repeated sprinting in hot and cool conditions on markers of gastrointestinal damage. Methods: Twenty-five, well-trained, nonheat acclimated male team-sport athletes completed a five-session, repeated-sprint training regimen over 7 days in either HOT (40 °C and 40% relative humidity [RH]) or COOL (20 °C and 40% RH) conditions. Participants underwent a 20-min warm-up and four sets of 5 × 6-s maximal cycling sprints, with 24-s rest and 5-min recovery between sets. Venous blood was collected pre-, post-, and 1 hr postexercise and analyzed for intestinal fatty acid binding protein, lipopolysaccharide binding protein, soluble CD14, and heat-shock protein. Results: Intestinal fatty acid binding protein concentrations were significantly increased (p < .004) postexercise (593 and 454 pg/ml) and 1 hr postexercise (466 and 410 pg/ml) on both Days 1 and 5 in HOT. Soluble CD14 increased by 398 and 308 ng/ml postexercise (p = .041), and lipopolysaccharide binding protein increased by 1,694 ng/ml postexercise on Day 1 in HOT (p < .05) and by 1,520 ng/ml on Day 5 in COOL (p = .026). Core and skin temperature, rating of perceived exertion, and thermal sensation were higher (p < .05) in HOT on Days 1 and 5 during sprinting. Conclusions: Repeated sprinting in the heat induced greater thermal strain and mild changes in gastrointestinal damage, likely attributable to the combination of environmental conditions and maximal-intensity exercise.

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Abstracts From the 2021 International Sport + Exercise Nutrition Conference

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Volume 32 (2022): Issue S1 (Feb 2022)

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Association Between Long-Term Regular Exercise and Gut Microbiota Among Middle-Aged and Older Urban Chinese

Jiajun Shi, Danxia Yu, Yaohua Yang, Hui Cai, Jie Wu, Qiuyin Cai, Jirong Long, Wei Zheng, Wanghong Xu, and Xiao-Ou Shu

Increasing evidence has suggested that physical activity may modulate gut microbiome composition. We investigated associations of long-term regular exercise with gut microbiota among middle-aged and older urban Chinese individuals. Gut microbiota was assessed using 16S ribosomal ribonucleic acid gene sequencing of stool samples from 2,151 participants from the Shanghai Women’s Health Study and Shanghai Men’s Health Study. Participants were free of cancer, diabetes, and cardiovascular diseases at the time of stool sample collection. Physical activity was assessed in repeat surveys between 1996 and 2015 using validated questionnaires. Regular exercise was defined as any type of leisure-time physical activity with a standard metabolic equivalent score >3.0. Stool samples were collected using the 95% ethanol method between 2015 and 2018 with an average of 3.0 years (SD = 0.9) after the latest exposure assessment. General linear regression and permutational multivariate analysis of variance were carried out to evaluate associations of microbial α- and β-diversity with regular exercise participation. Logistic regression and linear regression models were used to evaluate the prevalence and relative abundance of individual taxa in association with regular exercise. Regular exercise was significantly associated with β-diversity (Bray–Curtis and Jaccard dissimilarities, both false discovery rates = 0.03%, 0.12% and 0.09% variance explained, respectively) but not with α-diversity. Relative abundance of genus Ruminococcus was significantly lower among regular exercisers compared with nonexercisers (median relative abundance: 0.64% vs. 0.81%, false discovery rate <0.10). Further studies are needed to validate the findings from this study and evaluate health benefits of regular exercise on gut microbiota.

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Acute Ingestion of Ketone Monoesters and Precursors Do Not Enhance Endurance Exercise Performance: A Systematic Review and Meta-Analysis

Emma Brooks, Gilles Lamothe, Taniya S. Nagpal, Pascal Imbeault, Kristi Adamo, Jameel Kara, and Éric Doucet

There has been much consideration over whether exogenous ketone bodies have the capacity to enhance exercise performance through mechanisms such as altered substrate metabolism, accelerated recovery, or neurocognitive improvements. This systematic review aimed to determine the effects of both ketone precursors and monoesters on endurance exercise performance. A systematic search was conducted in PubMed, SPORTDiscus, and CINAHL for randomized controlled trials investigating endurance performance outcomes in response to ingestion of a ketone supplement compared to a nutritive or nonnutritive control in humans. A meta-analysis was performed to determine the standardized mean difference between interventions using a random-effects model. Hedge’s g and 95% confidence intervals (CI) were reported. The search yielded 569 articles, of which eight were included in this review (80 participants; 77 men and three women). When comparing endurance performance among all studies, no significant differences were found between ketone and control trials (Hedges g = 0.136; 95% CI [−0.195, 0.467]; p = .419). Subanalyses based on type of endurance tests showed no significant differences in time to exhaustion (Hedge’s g = −0.002; 95% CI [−0.312, 0.308]; p = .989) or time trial (Hedge’s g = 0.057; 95% CI [−0.282, 0.395]; p = .744) values. Based on these findings, exogenous ketone precursors and monoesters do not exert significant improvements on endurance exercise performance. While all studies reported an increase in blood ketone concentrations after ingestion, ketone monoesters appear to be more effective at raising concentrations than precursors.

Free access

Erratum: Fensham et al. (2021)

International Journal of Sport Nutrition and Exercise Metabolism

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Whey Protein Supplementation Is Superior to Leucine-Matched Collagen Peptides to Increase Muscle Thickness During a 10-Week Resistance Training Program in Untrained Young Adults

Jeferson L. Jacinto, João P. Nunes, Stefan H.M. Gorissen, Danila M.G. Capel, Andrea G. Bernardes, Alex S. Ribeiro, Edilson S. Cyrino, Stuart M. Phillips, and Andreo F. Aguiar

The purpose of this study was to investigate the effects of supplementation of whey protein (WP) versus leucine-matched collagen peptides (CP) on muscle thickness MT and performance after a resistance training (RT) program in young adults. Twenty-two healthy untrained participants were randomly assigned to either a WP (n = 11) or leucine-matched CP (n = 11) group and then submitted to a supervised 10-week RT program (3 days/week). The groups were supplemented with an equivalent amount of WP (35 g, containing 3.0 g of leucine) and CP (35 g, containing 1.0 g of leucine and 2.0 g of free leucine) during the intervention period (after each workout and in the evening on nontraining days). MT of the vastus lateralis and biceps brachii, isokinetic peak torque and mean power output of the elbow flexors, and peak power output of the lower body were assessed before and after the RT program. The WP group experienced a greater (interaction, p < .05) increase in the vastus lateralis (effect size, WP = 0.68 vs. CP = 0.38; % Δ, WP = 8.4 ± 2.5 vs. CP = 5.6 ± 2.6%) and biceps brachii muscle thickness (effect size, WP = 0.61 vs. CP = 0.35; % , WP = 10.1 ± 3.8 vs. CP = 6.0 ± 3.2%), with a similar increase in muscle performance (peak torque, mean power output, and peak power output) between groups (time p < .05). Supplementation with WP was superior to leucine content-matched CP supplementation in increasing muscle size, but not strength and power, after a 10-week RT program in young adults.