The aim of this thesis was to investigate the effects of whole-body vibrations (WBV) on neuromuscular fatigue or potentiation, and on the excitability of the α-motoneuron pool. Ten students (21.1 ± 1.41 years) took part in the study. The participants were instructed to maintain a semi-squat position (knee angle 60°, feet 40 cm apart) for several sets (18, 9 or 3) for the duration of 30, 60 or 180 seconds respectively (total time of 9 minutes on each visit). Three interventions were performed on the vibration platform turned on (frequency 26 Hz) and three on the vibration platform turned off. Knee extensors maximum voluntary contraction, level of voluntary activation and countermovement jumps were assessed before (PRED), immediately after (PO), 15 minutes after (PO15) and 30 minutes after (PO30) the intervention. Besides that, the soleus H reflex, knee extensors single twitch, double twitches and trains of stimulation were assessed during the rest periods between sets as well.
Interventions with short WBV intervals (30 & 60 s) induced a significant drop in H reflex compared to interventions without vibrations. The lack of neuromuscular potentiation registered in this study suggests that WBV should not be a replacement for traditional strength training in healthy individuals. This exercise modality should be used only when traditional strength training is contraindicated due to medical conditions.
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