Influence of carbohydrate-electrolyte drinks on marathon running performance

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Abstract
The aim of this study was to compare the effects of drinking two carbohydrate (CHO) electrolyte solutions and water on marathon running performance. Seven endurance-trained runners completed three 42.2-km treadmill time-trials which were randomly assigned and 4 weeks apart. On each occasion the subjects ingested 3 ml · Kg−1 body weight of either water (W), a 6.9% CHO solution (O) or a 5.5% CHO solution (L) immediately prior to the start of the run and 2 ml · kg−1 body weight every 5 km thereafter. The total volume of fluid ingested [mean (SEM)] was 1112 (42), 1116 (44) and 1100 (44) ml, respectively. Running times for W, O and L trials were 193.9 (5.0), 192.4 (3.3) and 190.0 (3.9) min, respectively. Performance time for the L trial was faster (P < 0.05) compared with that of the W trial. Running speed was maintained in the L trial, whereas it decreased after 10 km (P < 0.05) in the W and after 25 km (P < 0.05) in the O trial. Blood glucose and lactate, and hormonal responses to fluid ingestion were similar in all three trials. Higher plasma free fatty acid and glycerol concentrations were observed at the end of the W trial compared with those obtained after the O and L trials, respectively (P < 0.05). Plasma ammonia concentration was higher (P < 0.01) at the end of the L trial compared with the W trial. Plasma creatine kinase concentration was higher (P < 0.05) 24 h after the completion of the L trial than after the W trial. This study shows that the ingestion of a 5.5% CHO solution improves marathon running performance.

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