The effect of resistance exercise on substrate utilization during aerobic exercise in women

This study examined the effects of preceding aerobic exercise with resistance exercise on the respiratory exchange ratio (RER), and by inference, on the relative use of carbohydrate and fat during aerobic exercise. Twenty-four females were assessed for body composition, VO(2)max, activity, and dietary intake. Using a counterbalanced crossover design, each subject participated in two exercise trials: trial 1 (T-1)=30 min of aerobic exercise followed by 30 min of resistance exercise; trial 2 (T-2)=30 min of resistance exercise followed by 30 min of aerobic exercise. Dietary intake was controlled during the four days prior to each exercise trial. RER was significantly lower for T-2 than T-1 at min 5, 10, and 15. Rates of fat utilization were significantly greater in lean subjects (less than or equal to 20% body fat) during T-2, but not T-1. Results indicate that resistance exercise appears to increase fat utilization during the first 15 min of subsequent aerobic exercise and that leanness increases total fat utilization.