A portable vibrator for muscle performance enhancement by means of direct muscle tendon stimulation.

Combining vibration stimulation with conventional resistance training has gained in popularity. However, no portable vibrator capable of directly stimulating muscle tendon appears to feature in the literature. The aim of this study was the development of such a unit. The unit developed makes use of a rotating eccentric mass system to produce desired amplitude and frequency range capable of investigating the diverse vibration characteristics used in previous research studies. The effects of strapping force, joint angle and day-to-day repeatability on these vibration characteristics were investigated. In addition, muscle electromyography (EMG) activity was subsequently used to identify the optimum vibration amplitude and frequency. Finally, the repeatability of these EMG responses and effect of joint angle were examined. The unit was able to produce desired vibration characteristics (amplitude: 0.2-2 mm; frequency: 30-200 Hz). Test day, strapping force and joint angle had no significant effect on these characteristics (p>0.05). Both amplitudes (0.5 and 1.2 mm) and all three frequencies (30, 65 and 100 Hz) tested, significantly enhanced EMG activity (p<0.05), with 1.2 mm and both 65 and 100 Hz resulting in significantly greater enhancements (p<0.05). Joint angle had no significant effect on these EMG results (p>0.05). The day-to-day repeatability of EMG response was shown to be high (r=0.76-0.90).