The aim of this study was to examine if the pattern of fluid intake with a carbohydrate-electrolyte solution during 4 h recovery from prolonged, submaximal running would influence the subsequent endurance capacity. Seven well-trained athletes aged 19.8 ± 0.3 years (mean ± s(x̄) took part in the study, which had university ethical committee approval. They ran at 70% V̇O2 max on a level treadmill for 90 min (T1), or until volitional fatigue, whichever came first, on two occasions, at least 7-10 days apart. Four hours later, the subjects ran at the same speed for as long as possible (T2), as a measure of their endurance capacity. During the 4 h rehydration recovery period, the runners were allowed to drink a carbohydrate-electrolyte solution (6.9% Lucozade-Sport; sodium, 24 mmol l-1; potassium, 2.6 mmol l-1; calcium, 1.2 mmol l-1; osmolality, 300 mOsm kg-1) ad libitum on one occasion. On the other occasion, the volume of the same fluid was prescribed from calculations of the body mass loss during T1 (2.6% of pre-exercise body mass). All subjects completed the 90 min run during T1 on both trials. However, during T2, in the prescribed intake trial, the exercise time to exhaustion was 16% longer (P < 0.05) than during T2 in the ad libitum trial (69.9 ± 9.1 vs 60.2 ± 10.2 min). Although there was no difference between conditions in the total volume ingested (1499 ± 155 vs 1405 ± 215 ml), the volume of carbohydrate-electrolyte solution ingested in the fourth hour of the rehydration recovery period was greater in the prescribed intake trial than in the ad libitum trial (258 ± 52 vs 78 ± 34 ml; P < 0.05). The amount of glucose ingested in this period during the prescribed intake trial was also greater than during the ad libitum trial (17.8 ± 3.6 vs 5.4 ± 2.4 g; P < 0.05). There was a higher blood lactate concentration at the start of T2 in the prescribed intake trial than in the ad libitum trial (1.12 ± 0.20 vs 0.94 ± 0.09 mmol l-1; P < 0.05), but there were no differences in blood glucose, plasma insulin, free fatty acid concentrations or urine volume between trials. The results of this study suggest that drinking a prescribed volume of a carbohydrate-electrolyte solution after prolonged exercise, calculated to replace the body fluid losses, restores endurance capacity to a greater extent than ad libitum rehydration during 4 h of recovery, even though the total volumes ingested were the same between trials.
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