Abstract

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 took part in the study, which had university ethical committee approval. They ran at 70% VO2max 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; potassium, 2.6 mmol/l; calcium, 1.2 mmol/l; osmolality, 300 mOsm/kg) 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 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). 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), 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. Verf.-Referat