Regresar

The trampoline aftereVect: The motor and sensory modulations associated with jumping on an elastic surface

Abstract:

After repeated jumps over an elastic surface (e.g. a trampoline), subjects usually report a strange sensation when they jump again overground (e.g. they feel unable to jump because their body feels heavy). However, the motor and sensory eVects of exposure to an elastic surface are unknown. In the present study, we examined the motor and perceptual eVects of repeated jumps over two diVerent surfaces (stiV and elastic), measuring how this aVected maximal countermovement vertical jump (CMJ). Fourteen subjects participated in two counterbalanced sessions, 1 week apart. Each experimental session consisted of a series of maximal CMJs over a force plate before and after 1 min of light jumping on an elastic or stiV surface. We measured actual motor performance (height jump and leg stiVness during CMJ) and how that related to perceptual experience (jump height estimation and subjective sensation). After repeated jumps on an elastic surface, the Wrst CMJ showed a signiWcant increase in leg stiVness (P ≤ 0.01), decrease in jump height (P ≤ 0.01) increase in perceptual misestimation (P ≤ 0.05) and abnormal subjective sensation (P ≤ 0.001). These changes were not observed after repeated jumps on a rigid surface. In a complementary experiment, continuous surface transitions show that the eVects persist across cycles, and the eVects over the leg stiVness and subjective experience are minimized (P ≤ 0.05). We propose that these aftereVects could be the consequence of an erroneous internal model resulting from the high vertical forces produced by the elastic surface. © 2010 Springer-Verlag.