Abstract
PURPOSE: This study compared the effects of isocaloric beverages with differing proportions of carbohydrate and protein on markers of muscle recovery following heavy endurance exercise. METHODS: Twelve male cyclists (25.5±8.1 y, 65.5±7.1 ml/kg/min) completed an exercise trial consisting of 10 min at 60% Wmax, followed by a series of 2 min alternating-intensity intervals until fatigue (59.3±18.0 min, 13.2±4.5 high-intensity intervals). Following four hours of recovery, subjects completed a second exercise trial consisting of 20 minutes at 60% Wmax followed immediately by a simulated hilly 20-km time trial. Recovery beverages (∼300 kcal) were consumed immediately post-exercise, 2 hours post-exercise, and immediately following subsequent exercise. Beverages were randomly counterbalanced over three trials, each separated by ∼1 wk: CHO (75g CHO); high-carbohydrate/low-protein (HCLP: 45g CHO, 25g Pro, 0.5 g Fat); and low-carbohydrate/high-protein (LCHP: 8g CHO, 55g Pro, 4g Fat). RESULTS: Blood glucose levels obtained 30-min following beverage consumption were significantly different (p < 0.05) between LCHP (71.6±8.9 mg/dL), HCLP (88.0±16.9 mg/dL) and CHO (110.6±17.5 mg/dL). Serum insulin levels were similar between HCLP and CHO and these were significantly higher (p < 0.05) than LCHP. Subsequent exercise performance was not significantly different between treatments (LCHP 50.3±2.7 min; CHO 48.5±1.5 min; HCLP 48.8±2.1 min), although only 2 subjects had their best trial (and 5 their worst) with LCHP. In addition, no significant treatment effects were observed for changes in isometric peak torque of the quadriceps, serum creatine kinase, muscle soreness, or energy/fatigue ratings; which were measured pre-exercise, prior to subsequent exercise, and after an overnight recovery. CONCLUSION: Recovery beverages providing equal caloric content and differing proportions of carbohydrates/protein provided similar effects on markers of muscle recovery in well-trained cyclists. However, the elevated insulin response and tendency toward better subsequent performance with CHO and HCLP treatments suggest that higher proportions of carbohydrate are potentially advantageous for recovery from heavy endurance exercise. Supported by a research grant from Shaklee Corporation.
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