Comparison of leucine kinetics in endurance-trained and sedentary humans

Whole body leucine kinetics was compared in endurance-trained athletes and sedentary controls matched for age, gender, and body weight; Kinetic studie s were performed during 3 h of rest, 1 h of exercise (50% maximal oxygen co nsumption), and 2 h of recovery. When leucine kinetics were expressed both per unit of body weight and per unit of fat-free mass, both groups demonstr ated an increase in leucine oxidation during exercise (P < 0.01). Trained a thletes had a greater leucine rate of appearance during exercise and recove ry compared with their sedentary counterparts (P < 0.05) and an increased l eucine oxidation at all times on the basis of body weight (P < 0.05). Howev er, all of these between-group differences were eliminated when leucine kin etics were corrected for fat-free tissue mass. Therefore, correction of leu cine kinetics for fat-free mass may be important when cross-sectional inves tigations on humans are performed. Furthermore, leucine oxidation, when exp ressed relative to whole-body oxygen consumption during exercise, was simil ar between groups. It is concluded that there was no difference between end urance-trained and sedentary humans in whole body leucine kinetics during r est, exercise, or recovery when expressed per unit of fat-free tissue mass.