No abstract

The aim of this study was to examine the effects of ingesting a carbohydrate-electrolyte solution on endurance capacity during a prolonged intermittent, high-intensity shuttle running test (PIHSRT). Nine trained male games players performed two exercise trials, 7 days apart. On each occasion, they completed 75 min exercise, comprising of five 15-min periods of intermittent running, consisting of sprinting, interspersed with periods of jogging and walking (Part A), followed by intermittent running to fatigue (Part B). The subjects were randomly allocated either a 6.9% carbohydrate-electrolyte solution (CHO) or a non-carbohydrate placebo (CON) immediately prior to exercise (5 ml kg-1 body mass) and every 15 min thereafter (2 ml kg-1 body mass). Venous blood samples were obtained at rest, during and after each PIHSRT for the determination of glucose, lactate, plasma free fatty acid, glycerol, ammonia, and serum insulin and electrolyte concentrations. During Part B, the subjects were able to continue running longer when fed CHO (CHO = 8.9 +/- 1.5 min vs CON = 6.7 +/- 1.0 min; P < 0.05) (mean +/- S.E.M.). These results show that drinking a carbohydrate-electrolyte solution improves endurance running capacity during prolonged intermittent exercise.

The present study was designed to examine the effects of mixed high-carbohydrate meals with different glycaemic indices (GI) on substrate utilization during subsequent exercise. Nine healthy male recreational runners (age 26·8 (SEM 1·1) years, body mass 74·7 (SEM 2·4) kg, V O 2 max 58·1 (SEM 1·7) ml/kg per min) completed three trials: high-glycaemic-index meal (HGI), low-glycaemic-index meal (LGI) and fasting (FAST), separated by 7 d. The test meals contained 2 g carbohydrate/kg body mass, they were isoenergetic and the GI values were 77·4, 36·9 and 0·0 respectively. In each trial, subjects consumed the test meal 3 h before performing a 60 min run at 65 % V O 2 max on a motorized treadmill. Ingestion of the HGI and LGI resulted in hyperglycaemia and hyperinsulinaemia during the postprandial period compared with the FAST (P, 0·05). The incremental area under the curve for plasma glucose was 2-fold higher for HGI compared with LGI (108·7 v. 48·9 mmol/l per min). In contrast, plasma non-esterified fatty acid concentrations were significantly lower following HGI and LGI compared with FAST (P, 0·05). During the subsequent submaximal exercise, plasma glucose declined to below the fasting value in HGI compared with LGI and FAST (P, 0·05). The estimated total fat oxidation was significantly higher for the LGI than the HGI during exercise (P,0·05). In summary, both pre-exercise carbohydrate meals resulted in lower rates of fat oxidation during subsequent exercise than when subjects performed exercise in the fasting state. However, the LGI resulted in a higher rate of fat oxidation during exercise than following the consumption of the HGI.

Ingestion of a carbohydrate-electrolyte solution during exercise enabled subjects with compromised glycogen stores to better maintain skill and sprint performance than when ingesting fluid alone.

The aim of the present study was to investigate whether 2 weeks of vitamin C supplementation affects recovery from an unaccustomed bout of exercise. Sixteen male subjects were allocated to either a placebo (P; n = 8) or vitamin C group (VC; n = 8). The VC group consumed 200 mg of ascorbic acid twice a day, whereas the P group consumed identical capsules containing 200 mg of lactose. Subjects performed a prolonged (90-min) intermittent shuttle-running test 14 days after supplementation began. Post-exercise serum creatine kinase activities and myoglobin concentrations were unaffected by supplementation. However, vitamin C supplementation had modest beneficial effects on muscle soreness, muscle function, and plasma concentrations of malondialdehyde. Furthermore, although plasma interleukin-6 increased immediately after exercise in both groups, values in the VC group were lower than in the P group 2 hours after exercise (p < .05). These results suggest that prolonged vitamin C supplementation has some modest beneficial effects on recovery from unaccustomed exercise.