The Rate of Leg Fat Oxidation Is Not Attenuated During Incremental Intensity One‐Leg Knee Extensor Exercise

ABSTRACT It is not clear if fat oxidation is attenuated at higher exercise intensities, when exercising with a small muscle mass, and therefore, we studied leg fat oxidation during graded one‐leg exercise. Ten males (age: 27 ± 2 years, body mass: 82 ± 3 kg, BMI: 24 ± 1 kg m−2, V̇O2max: 49 ± 2 mL min−1 kg−1) performed one‐leg exercise at 25% of maximal workload (Wmax) for 30 min, followed by 120‐min exercise at 55% Wmax with the contralateral leg, and finally 30‐min exercise at 85% Wmax with the first leg. Blood was sampled from an artery and both femoral veins, and blood flow was determined using Doppler ultrasound. Muscle biopsies were obtained before and after 30 min at each workload. One‐way RM ANOVA was applied to determine the impact of exercise intensity. Data are expressed as mean ± SEM. From rest through exercise average blood flow (0.4 ± 0.1, 2.1 ± 0.1, 2.6 ± 0.2, 3.7 ± 0.2 L min−1) and oxygen uptake across the leg (0.03 ± 0.01, 0.23 ± 0.02, 0.35 ± 0.03, 0.53 ± 0.04 L min−1) increased with exercise intensity (p