IS ELASTIC ENERGY-STORAGE OF QUANTITATIVE RELEVANCE FOR THE FUNCTIONAL-MORPHOLOGY OF THE HUMAN LOCOMOTOR APPARATUS

Elastic storage of energy in the vertebrate locomotor apparatus is sup posed to be an important functional factor in cyclic and acyclic movem ents. In terms of physics, for humans a proof for the occurence and qu antitative relevance of this phenomenon in vivo and under physiologica l conditions has been missing until now. In addition to the large amou nt of plausible, but inconclusive information about elasticity in huma ns and animals, we describe a simple experiment to prove the existence of quantitatively relevant elastic energy storage in the human locomo tor apparatus. Ten volunteers (5 female, 5 male) each assumed a relaxe d, upright posture on a steel platform. After the release of a support , the volunteers and the platform fell for a defined distance of 33 mm . Loaded with the volunteers, the platform fell significantly (p<0.001 ) faster than predicted by the laws of stiff body mechanics (50 vs. 82 ms). For a minimum time of 50 ms, the human locomotor apparatus is ab le to support an average external power output of more than 400 W by m eans of an energy transfer of more than 20 J. During the fall, no EMG activities of the ankle flexors could be recorded, We conclude that th e acceleration of the platform fall is induced by elastic elements ser ving as energy sources. Elastic energy storage is of quantitative rele vance for the functional morphology and biomechanics of the human loco motor apparatus.