Scand J Med Sci Sports, 2011
The effect of whole body vibration on the H-reflex, the stretch reflex, and the short-latency response during hopping.
Ritzmann R, Kramer A, Gollhofer A, Taube W
Institute of Sport and Sport Science, University of Freiburg, Freiburg, Germany.
The effect of whole body vibration (WBV) on reflex responses is controversially discussed in the literature.
PURPOSE: In this study, three different modalities of reflex activation with increased motor complexity have been selected to clarify the effects of acute WBV on reflex activation: 1) the electrically evoked H-reflex, 2) the mechanically elicited stretch reflex, and 3) the short-latency response (SLR) during hopping.
METHOD: WBV-induced changes of the H-reflex, the stretch reflex, and the SLR during hopping were recorded in the soleus and gastrocnemius muscles and were analyzed before, during (only the H-reflex), immediately after, 5 min and 10 min after WBV.
RESULTS: The main findings were that: 1) the H-reflexes were significantly reduced during and at least up to 5 min after WBV, 2) the stretch reflex amplitudes were also significantly reduced immediately after WBV but recovered to their initial amplitudes within 5 min, and 3) the SLR during hopping showed no vibration-induced modulation. With regard to the modalities with low motor complexities, the decreased H- and stretch reflex responses are assumed to point toward a reduced Ia afferent transmission during and after WBV. However, it is assumed that during hopping, the suppression of reflex sensitivity is compensated by facilitatory mechanisms in this complex motor task.