Substrate oxidation during incremental arm and leg exercise in men and women matched for ventilatory threshold

The aim of this study was to determine the variations in substrate utilization between men and women matched for ventilatory threshold (T_vent) during incremental arm cranking and leg cycling exercise at 70, 85, 100 and 115% of the mode-specific T_vent. Recreationally active men (n = 12) and women (n = 10) with similar values for percentage of peak oxygen consumption at T_vent participated in the study. Ventilatory equivalence, excess CO₂ and modified V-slope methods were used concurrently to determine T_vent. The participants performed 5 min of exercise at each of 70, 85, 100 and 115% T_vent during both arm cranking and leg cycling exercise. The females were tested during the early follicular phase for all trials. A two-way mixed-design analysis of variance was performed to test for differences between the sexes. When carbohydrate and fat oxidation were expressed relative to total fat-free mass, carbohydrate oxidation during arm cranking and leg cycling was significantly higher in men than women at each percentage of T_vent. In contrast, women showed significantly higher fat oxidation across intensities during both arm cranking and leg cycling. Our results suggest that when substrate utilization is expressed relative to total fat-free mass, women appear to maintain a higher rate of fat and lower rate of carbohydrate oxidation than men during both incremental arm cranking and leg cycling exercise relative to T_vent.