Effects of short- and long-term vibration therapy on maximum voluntary isometric contraction and muscle activity in quadriceps and antagonist muscles

[Purpose] Vibratory stimulation is used to restore motor function in patients with residual motor impairments. However, to date, no studies have examined its effects on both the stimulated and antagonist muscles at different intervention time points. We thus examined the effects of short- and long-term vibratory stimulation on maximum voluntary isometric contractions (MVIC) and electromyography (EMG) of the quadriceps and antagonist muscles. [Participants and Methods] A crossover design was employed with 18 healthy male participants who performed maximal knee extensions and flexions under three separate conditions: control, short-term vibration stimulation (15 s), and long-term vibration stimulation (5 min). The rectus femoris was stimulated at a vibration frequency of 108 Hz. MVIC was evaluated in the quadriceps and antagonist muscles, and EMG was recorded during MVIC assessment. EMG analysis included the integrated electromyogram (IEMG) and median frequency (MF). [Results] Knee extension MVIC did not differ significantly between control and short-term vibration groups. However, it was significantly increased in the long-term vibration group relative to the control group. No differences in IEMG and MF were observed. [Conclusion] In this study, an increase in knee extension MVIC was observed after 5 min of rectus femoris stimulation.