The Bang-bang Phase of Maximal Height Jumps by Humans

Abstract Subjects were instructed to jump as high as possible starting from a deep squat either with their feet flat on the floor or on their toes. For simplicity of analysis, each subject was instructed to keep his arms extended above his head. These jumps were also studied by computer implementation of an optimal control model. The model consists of a 4-segment inverted pendulum that is to be propelled as high as possible by coordinating the activation of three muscle groups which produce torque at the ankle, knee and hips. The dynamic model used for torque generation incorporates isometric torque-angle and isokinetic torque-angle data obtained from the subjects. Earlier research has shown that maximal height jumps can be divided into three epochs. The results presented here suggest that single-joint extensor muscles are maximally activated and flexor muscles inactivated in the final epoch of the jump. Furthermore, the height of the jump appears more strongly dependent on muscular coordination than on muscular strength. Acknowledgements. This work was supported by NIH grant NS17662 and the Veterans Administration. We are grateful to Professor Sten Gillner for allowing us to conduct the experiments in his laboratory at Stockholm. We thank Carol Cady for her assistance in figure preparation and Patsy Keehn for typing