ABSTRACT
Whole-body vibration (WBV) has been suggested to have a beneficial effect on muscle strength. Manufacturers of vibration platforms promote WBV as an effective alternative or complement to resistance training. This study aimed to review systematically the current (August 2005) scientific support for effects of WBV on muscle strength and jump performance. MEDLINE and SPORT DISCUS were searched for the word vibration in combination with strength or training. Twelve articles were included in the final analysis. In four of the five studies that used an adequate design with a control group performing the same exercises as the WBV group, no difference in performance improvement was found between groups, suggesting no or only minor additional effects of WBV as such. Proposed neural mechanisms are discussed.
Subject(s)
Exercise/physiology , Muscle Strength , Physical Education and Training/methods , Vibration , HumansABSTRACT
Despite higher neural activation during active as compared to passive muscle shortening, Hoffman reflexes (H-reflexes) are similar. This may be explained by homosynaptic post-activation depression (HPAD) of Ia-afferents being present during active shortening. Accordingly, it was investigated whether conditioning electrical stimulation of the tibial nerve reduced the H-reflex less during active than passive shortening. The effects of two conditioning modes (0.2 and 1 Hz) were compared to a control mode without conditioning. H-reflexes and M-waves were elicited as the ankle passed 90 degrees with the soleus muscle undergoing passive or active (20% MVC) lengthening or shortening. Conditioning had no effect during active shortening. In contrast, during passive shortening, the H:M of the 1 Hz mode was significantly less than that of the 0.2 Hz and control modes. In lengthening, H:M was unaffected by conditioning. These findings support that HPAD reduces the synaptic efficacy of Ia-afferents during active shortening, active and passive lengthening, but not passive shortening.
