Biomechanics of locomotion in subgravity

The speed of walking or running on the moon as compared with earth is appreciably reduced, in spite of mechanisms of compensation taking place such a forward leaning of the body and an increase of the horizontal component of the push of the foot on the ground. However on the moon the same speed of locomotion as on earth can be reached by shifting to a different mechanism of locomotion, i. e. progression by jumps, which becomes possible on the moon because of the reduction of the body weight. The energy cost of locomotion is certainly less on the moon than on earth, about 1/6. Were the subject not restrained by the space suit, progression by jumps at 20 km hr-1 on the moon would cost no more than 10 ml kg-1 min-1 of oxygen, the same as walking on earth at 6 km hr-1. Maximal acceleration of the body as in sprinting, or deceleration as in stopping, attains much higher values on earth than on the moon. While sprinting on earth may involve the maximal muscular power, sprinting or progressing at the highest speed on the moon involves only a fraction of the maximal power, mainly because of the reduced maximal frequency of the steps (or jumps). The maximal height of the jump on both feet on the moon could attain 4 m in the unrestricted subject. An analysis is wanted on the restriction of the movements brought about by the space suit and on the energy cost of progression.