Adaptability of a jump movement pattern to a non-constant force field elicited via centrifugation.

Humans are accustomed to Earth's constant gravitational acceleration of 1g. Here we assessed if complex movements such as jumps can be adapted to different acceleration levels in a non-constant force field elicited through centrifugation. Kinematics, kinetics and muscle activity of 14 male subjects (age 27±5years, body mass 77±6kg, height 181±7cm) were recorded during repetitive hopping in a short-arm human centrifuge for five different acceleration levels (0.5g, 0.75g, 1g, 1.25g, 1.5g). These data were compared to those recorded during normal hops on the ground, and hops in a previously validated sledge jump system. Increasing acceleration from 0.5g to 1.5g resulted in increased peak ground reaction forces (+80%, p<0.001), rate of force development (+100%, p<0.001) and muscle activity (+30 to +140%, depending on phase, side and muscle). However, most of the recorded parameters did not attain the level observed for jumps on the ground or in the jump system. For instance, peak forces during centrifugation with 1g amounted to 60% of the peak forces during jumps on the ground, ground contact time was prolonged by 90%, and knee joint excursions were reduced by 50%. We conclude that in principle, a quick adaptation to acceleration levels other than the normal constant gravitational acceleration of 1g is possible, even in the presence of a non-constant force field and Coriolis forces. However, centrifugation introduced additional constraints compared to a constant force field without rotation, resulting in lower peak forces and changes in kinematics. These changes can be interpreted as a movement strategy aimed at reducing lower limb deflections caused by Coriolis forces.