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Fluid Needs for Training, Competition, and Recovery in Track-and-Field Athletes

Douglas J. Casa, Samuel N. Cheuvront, Stuart D. Galloway, and Susan M. Shirreffs

The 2019 International Amateur Athletics Federation Track-and-Field World Championships will take place in Qatar in the Middle East. The 2020 Summer Olympics will take place in Tokyo, Japan. It is quite likely that these events may set the record for hottest competitions in the recorded history of both the Track-and-Field World Championships and Olympic Games. Given the extreme heat in which track-and-field athletes will need to train and compete for these games, the importance of hydration is amplified more than in previous years. The diverse nature of track-and-field events, training programs, and individuality of athletes taking part inevitably means that fluid needs will be highly variable. Track-and-field events can be classified as low, moderate, or high risk for dehydration based on typical training and competition scenarios, fluid availability, and anticipated sweat losses. This paper reviews the risks of dehydration and potential consequences to performance in track-and-field events. The authors also discuss strategies for mitigating the risk of dehydration.

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Effect of Exercise Intensity on Subsequent Gastric Emptying Rate in Humans

Gethin H. Evans, Phillip Watson, Susan M. Shirreffs, and Ronald J. Maughan

Previous investigations have suggested that exercise at intensities greater than 70% maximal oxygen uptake (VO2max) reduces gastric emptying rate during exercise, but little is known about the effect of exercise intensity on gastric emptying in the postexercise period. To examine this, 8 healthy participants completed 3 experimental trials that included 30 min of rest (R), low-intensity (L; 33% of peak power output) exercise, or high-intensity (H; 10 × 1 min at peak power output followed by 2 min rest) exercise. Thirty minutes after completion of exercise, participants ingested 595 ml of a 5% glucose solution, and gastric emptying rate was assessed via the double-sampling gastric aspiration method for 60 min. No differences (p > .05) were observed in emptying characteristics for total stomach volume or test meal volume between the trials, and the quantity of glucose delivered to the intestine did not differ between trials (p > .05). Half-emptying times did not differ (p = .902) between trials and amounted to 22 ± 9, 22 ± 9, and 22 ± 7 min (M ± SD) during the R, L, and H trials, respectively. These results suggest that exercise has little effect on postexercise gastric emptying rate of a glucose solution.

Open access

IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete

Ronald J. Maughan, Louise M. Burke, Jiri Dvorak, D. Enette Larson-Meyer, Peter Peeling, Stuart M. Phillips, Eric S. Rawson, Neil P. Walsh, Ina Garthe, Hans Geyer, Romain Meeusen, Luc van Loon, Susan M. Shirreffs, Lawrence L. Spriet, Mark Stuart, Alan Vernec, Kevin Currell, Vidya M. Ali, Richard G.M. Budgett, Arne Ljungqvist, Margo Mountjoy, Yannis Pitsiladis, Torbjørn Soligard, Uğur Erdener, and Lars Engebretsen

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition program. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including the management of micronutrient deficiencies, supply of convenient forms of energy and macronutrients, and provision of direct benefits to performance or indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can offer benefits to the athlete, but others may be harmful to the athlete’s health, performance, and/or livelihood and reputation if an anti-doping rule violation results. A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome, and habitual diet. Supplements intended to enhance performance should be thoroughly trialed in training or simulated competition before implementation in competition. Inadvertent ingestion of substances prohibited under the anti-doping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete’s health and awareness of the potential for harm must be paramount, and expert professional opinion and assistance is strongly advised before embarking on supplement use.