Influence of fluid ingestion and carbohydrate supplementation on physical and mental performance during intermittent high-intensity exercise

Abstract

Carbohydrate (CHO) ingestion results in positive effects on exercise capacity, repeated sprint speed and sport-specific skill performance during intermittent exercise. This study evaluated the effects of lower concentrations of CHO on performance during intermittent exercise. Ten healthy males (mean±SD age 25±3 years; height 1.75±0.06 m; mass 75.9±6.4 kg; VO2max54.2±5.0 ml/kg/min) completed four 15-min periods of intermittent running, consisting of maximal sprinting interspersed with periods of running and walking (Loughborough Intermittent Shuttle Test). This was followed by the multistage shuttle-running fitness test (MSFT) to volitional exhaustion. Subjects consumed 3 ml/kg body mass of plain water, a 3% CHO solution or a 6% CHO solution before exercise and a further 1.5 ml/kg body mass of the appropriate drink after each 15-min block. A trial with no fluid ingestion was also completed. Sprint time, heart rate, core temperature, perceived exertion and thermal stress were recorded at regular intervals. Cognitive function was assessed using a computer-based test battery. Time to exhaustion in the MSFT was 9.9±2.0 min, 10.2±2.0 min, 10.9±1.9 min and 11.2±1.8 min in the no fluid, water, 3% and 6% CHO trials, respectively (p=0.004). Core temperature reached 38.9±0.4°C during the no fluid trial, 38.5±0.4°C in the water trial and 38.6±0.3°C at the end of the CHO trials (p=0.011). There was no change in response times to a visual search task in the no fluid and water trials, but CHO ingestion improved response times after exercise (3% CHO, p=0.036; 6% CHO, p=0.041). These data suggest that drinks containing lower CHO concentrations can produce improvements in exercise capacity and motor response times similar to those observed with the ingestion of the amounts of CHO found in many sports drinks. The study was carried out in relation to the product Powerade and was funded in part by The Coca-Cola Company.