Effects of meal form and composition on plasma testosterone, cortisol, andinsulin following resistance exercise

The purpose of this study was to examine the effects of postexercise feedin g on plasma levels of insulin, testosterone, cortisol, and testosterone:cor tisol (T:C). Ten experienced, resistance trained males (20.7 +/- 0.95 years ) were given whole food (WF: protein 38 g; carbohydrate 70 g; fat 7 g), a s upplemental drink (SD; isocaloric and isonitrogenous to WF), an isocaloric carbohydrate beverage (C), or a placebo beverage (P) immediately, 2 and 4 h ours after a standardized weight training protocol on 4 days, each separate d by 1 week, in a repeated measures design. Subjects also received a standa rdized meal at 7 and 12 hours postexercise. Insulin, testosterone, and cort isol were measured pre-exercise and during 24 hours of recovery (at 0.5, 2. 5, 4.5, 8, and 24 hours) using venous blood samples. Significant (condition x time) interactions were found for insulin, testosterone, and T:C, but no t for cortisol (p < .05). The SD yielded a greater response for insulin tha n all other conditions. Conversely, P demonstrated the greatest values for testosterone and T:C at 2.5 and 4.5 hours postexercise. Cortisol did not va ry between conditions and there were no condition effects for insulin, test osterone, cortisol, and T:C at 8 or 24 hours. In conclusion, the efficacy o f postexercise feeding for optimizing T:C and muscle growth is unclear; how ever, consumption of SD appears to maximize circulating insulin for several hours following resistance exercise.