Researchers designed a study to test both the acute and long-term responses to drinking carbohydrate drinks during weight-training workouts.1 In the first part of the study seven men, average age 21, fasted for four hours, then trained on a nine-station weight-training routine, doing three sets of 10 reps per exercise and using a weight equal to 75 percent of their one-rep maximums. During one workout the men drank a zero-calorie placebo drink, and during the next session they drank a formula containing 6 percent carbs.
In the long-term part of the study two groups of men drank the zero-calorie placebo or the 6 percent carb drink for 12 weeks while training. In the first, or short-term, study the carb drink caused elevated blood glucose and insulin levels, which led to a significant blunting of cortisol release. Cortisol rose only 7 percent in the carb-drink group and 99 percent in the placebo group. The same thing occurred during the long-term part of the study’those getting the carb drink had significantly lower cortisol levels during workouts than those drinking the placebo.
Even more significant, however, was the resulting muscular growth in the carb group. After 12 weeks those subjects showed a 19.1 percent increase in type 1 muscle fiber area and a 22.5 percent increase in type 2 muscle fiber area over what the zero-calorie-drink group experienced. The greater gains were attributed to the blunted cortisol-release effect. A drink containing more than 8 percent carbs, however, may interfere with fluid uptake during exercise and lead to unpleasant gastrointestinal symptoms.
1 Tarpenning, K.M., et al. (2001). Influence of weight-training exercise and modification of hormonal response on skeletal muscle growth. J Science and Medicine in Sport. 4:431-436.
Editor’s note: Phosphatidylserine has also been shown to blunt cortisol release. For more information see page 174 of the August '02 IRONMAN.