Carbohydrate ingestion during team games exercise: current knowledge and areas for future investigation
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There is a growing body of research on the influence of ingesting carbohydrate-electrolyte (CHO-E) solutions immediately prior to and during prolonged intermittent, high-intensity exercise (team games exercise) designed to replicate field-based team games. This review presents the current body of knowledge in this area, and identifies avenues of further research. Almost all early work supported the ingestion of CHO-E solutions during prolonged intermittent exercise, but was subject to methodological limitations. A key concern was the use of exercise protocols characterised by prolonged periods at the same exercise intensity, the lack of maximal or high-intensity work components, and long periods of seated recovery, that failed to replicate the activity pattern or physiological demand of team games exercise. The advent of protocols specifically designed to replicate the demands of field-based team games enabled a more externally valid assessment of the influence of carbohydrate (CHO) ingestion during this form of exercise. Once again, the research overwhelmingly supports CHO ingestion immediately prior to and during team games exercise for improving time to exhaustion during intermittent running. While the external validity of exhaustive exercise at fixed prescribed intensities as an assessment of exercise capacity during team games may appear questionable, these assessments should perhaps not be viewed as exhaustive exercise tests per se but as indicators of the ability to maintain high-intensity exercise, which is a recognised marker of performance and fatigue during field-based team games. Possible mechanisms of enhancement include sparing of muscle glycogen, glycogen resynthesis during low-intensity exercise periods, and attenuated effort perception during exercise. Most research fails to show improvements in sprint performance during team games exercise with CHO ingestion, perhaps due to the lack of influence of CHO on sprint performance when endogenous muscle glycogen concentration remains above a critical threshold of ~200 mmol/kg dry weight. Despite the increasing number of publications in this area, few studies have attempted to drive the research base forwards by investigating potential modulators of CHO efficacy during team games exercise, preventing the formulation of optimal CHO intake guidelines. Potential modulators may be different to those during prolonged steady-state exercise due to the constantly changing exercise intensity and frequency, duration and intensity of rest intervals, the potential for team games exercise to slow the rate of gastric emptying, and restricted access to CHO-E solutions during many team games. This review has highlighted fluid volume, CHO concentration, CHO composition and solution osmolality; glycaemic index of pre-exercise meals; fluid and CHO ingestion patterns; fluid temperature; CHO mouthwashes; CHO supplementation in different ambient temperatures; and investigation of all of these areas in different subject populations as important avenues for future research to enable a more comprehensive understanding of CHO ingestion during team games exercise.
RightsReproduced from Sports Medicine 2011: 41 (7): 559-585 with permission from Adis (© Adis Data Information BV 2012. All rights reserved). Available from http://dx.doi.org/10.2165/11589150-000000000-00000
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