In ̄uence of vibration on mechanical power and electromyogram activity in human arm ̄exor muscles

The aim of this study was to evaluate the in̄uence of vibration on the mechanical properties of arm ̄exors. A group of 12 international level boxers, all members of the Italian national team, voluntarily participated in the experiment: all were engaged in regular boxing training. At the beginning of the study they were tested whilst performing forearm ̄exion with an extra load equal to 5% of the subjects' body mass. Following this, one arm was given the experimental treatment (E; mechanical vibration) and the other was the control (no treatment). The E treatment consisted of ®ve repetitions lasting 1-min each of mechanical vibration applied during arm ̄exion in isometric conditions with 1 min rest between them. Further tests were performed 5 min immediately after the treatment on both limbs. The results showed statistically signi®cant enhancement of the average power in the arm treated with vibrations. The root mean square electromyogram (EMGrms) had not changed following the treatment but, when divided by mechanical power, (P) as an index of neural eciency, it showed statistically signi®cant increases. It was concluded that mechanical vibrations enhanced muscle P and decreased the related EMG/P relationship in elite athletes. Moreover, the analysis of EMGrms recorded before the treatment and during the treatment itself showed an enormous increase in neural activity during vibration up to more than twice the baseline values. This would indicate that this type of treatment is able to stimulate the neuromuscular system more than other treatments used to improve neuromuscular properties.