ENERGY-EXPENDITURE AND MOTOR-PERFORMANCE RELATIONSHIPS IN HUMANS LEARNING A MOTOR TASK

The ability of human subjects to learn minimum energy-demanding varian ts of biological motion was examined in three adult males trained to w alk on hands and feet (creep) on a motor-driven treadmill at constant speed (0.64 m/s) for 16 3-min trials. Two subjects systematically decr eased oxygen consumption and heart rate over trials. Following this ac quisition phase, subjects completed walking and creeping trials at pos itive and negative treadmill grades and selected a freely chosen creep ing grade that felt ''most comfortable.'' One subject selected a grade that was more efficient than those imposed. Oxygen-consumption curves for walking and creeping converged with increasing positive grade, in dicating that increased grade influences the metabolic energy viabilit y of the task (creeping or walking). The acquisition data provide empi rical support for the ''principle of least effort'' and lend support t o the concept of a ''comfort mode'' in the execution of motor tasks.