OPTIMIZATION OF HUMAN-POWERED ELASTIC MECHANISMS FOR ENDURANCE AMPLIFICATION

Throughout the human body hundreds of muscles exert forces to stiffen and move the limbs and torso. During heavy exercise, only a small port ion of these muscles fatigue. We report here a new kind of human-power ed mechanism which amplifies endurance by altering the distribution of work output between fatiguing and nonfatiguing muscles. During heavy exercise, springs within the mechanism are stretched by muscles which would not fatigue if the exercise were conducted without the mechanism . This stored energy is then used to assist those muscles which typica lly would fatigue, resulting in an increase in endurance. A mathematic al model is used to predict the efficiency with which the body can per form mechanical work at various spring stiffnesses for a particular he avy-exercise activity and mechanism. The model results support the hyp othesis that the spring stiffnesses which maximize endurance also maxi mize the efficiency with which the human body can perform work.