Author(s): YOSHINAGA, R., KIMURA, T., Institution: KOBE UNIVERSITY, Country: JAPAN, Abstract-ID: 1312

INTRODUCTION:
Various devices, including percussive massage devices, have been introduced to stimulate skeletal muscle with the aim of enhancing muscle performance. However, physiological evidence regarding the effects of vibration on muscle force output remains limited (1). Rather, long-lasting muscle or tendon vibration is known to attenuate maximal voluntary contraction (MVC) force, possibly due to presynaptic inhibition and/or depletion of neurotransmitter at Ia terminals (2, 3). In contrast, during short-duration vibration (<20 s), most Ia fibers discharged harmonically in response to tendon vibrations up to 80–100 Hz (4). In addition, while short-duration vibration enhanced voluntary activation in the tibialis anterior muscle only in the fatigued state (5), its effect on the fresh muscle may be observed in the plantar flexor muscles because these muscles are inherently more difficult to maximally drive than the tibialis anterior muscle (6). Accordingly, the aim of this study was to explore the effects of short-duration tendon vibration at 100 Hz on maximal force output of the plantar flexors.
METHODS:
Ten young healthy adults (21–24 years) performed an isometric plantar flexion task with their dominant leg. Participants were instructed to produce maximal force as quickly as possible (3). During the task, a vibrator (TMT-18; Heiwa Denshi, Japan) was attached to the Achilles tendon. Participants completed five sets of two maximal trials. In each set, two conditions were applied in random order: the control (CON) and vibration (VIB) conditions. In the CON condition, no vibration was applied during maximal contraction; in the VIB condition, they initiated maximal contraction approximately 1 s after the onset of 100-Hz tendon vibration. During the trials, surface electromyograms (sEMG) were recorded from the medial and lateral heads of the gastrocnemius muscle and the tibialis anterior muscle. After each trial, participants’ subjective achievement was assessed.
RESULTS:
Peak force was not affected by the vibration condition. However, the peak dF/dt was significantly lower in the VIB condition (P = 0.029, dz = 0.818). For EMG RMS values, no significant differences were observed between conditions. On the other hand, the coefficient of variation of subjective achievement tended to be lower in the VIB condition (P = 0.090, r = 0.707).
CONCLUSION:
Consistent with previous studies using long-lasting vibration (3), peak dF/dt was attenuated even with short-duration tendon vibration. Future studies should optimize vibration parameters such as frequency, duration, and location.
REFERENCES:
1) Ferreira et al. J Funct Morphol Kinesiol 8:138, 2023.
2) Bongiovanni et al. J Physiol 423:15-26, 1990
3) Kouzaki et al. J Appl Physiol 89:1420-1424, 2000.
4) Roll et al. Exp Brain Res 76:213-222, 1989
5) Bongiovanni et al. J Physiol 423:1-14, 1990
6) Belanger & McComas. J Appl Physiol 51:1131-1135, 1981.