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Neuromuscular responses of the plantar flexors to whole‐body vibration
Author(s) -
Harwood B.,
Scherer J.,
Brown R. E.,
Cornett K. M. D.,
Kenno K. A.,
Jakobi J. M.
Publication year - 2017
Publication title -
scandinavian journal of medicine and science in sports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.575
H-Index - 115
eISSN - 1600-0838
pISSN - 0905-7188
DOI - 10.1111/sms.12803
Subject(s) - plantar flexion , whole body vibration , electromyography , medicine , h reflex , reflex , soleus muscle , physical medicine and rehabilitation , muscle spindle , afferent , endocrinology , anatomy , ankle , skeletal muscle , physics , quantum mechanics , vibration
Enhanced physical performance following whole‐body vibration (WBV) has been attributed to increased muscle activity; however, few studies have measured the mechanisms underlying these changes. The objective of this study was to measure the responsiveness of the Ia pathway as well as contractile properties in 16 young adults (24±2 years, eight men, eight women) following repeated bouts of acute WBV (45 Hz, 2 mm). Hoffman reflexes (H‐reflex), compound muscle action potentials (M‐wave), and twitch contractile properties were measured prior to and immediately following five 1‐minute WBV exposures, and at 3, 5, 10, and 20 minute post‐WBV. M‐wave and H‐reflex amplitudes decreased by 8% ( P <.001) and by 46% ( P <.05), respectively, whereas peak twitch torque decreased by 9% ( P <.01) and rate of twitch torque development slowed 8% ( P <.05). Percent voluntary activation and maximal plantar flexor torque were unchanged as a consequence of WBV ( P >.05). In response to acute WBV, the root mean square of the soleus electromyography signal (EMG RMS ) increased by 8%, while the EMG RMS of the lateral gastrocnemius increased by 3% ( P <.05). These data indicate that the responsiveness of the Ia pathway is diminished and contractile function is impaired immediately following WBV, and that the neural mechanisms underlying improved performance following WBV lie in alternative hypotheses possibly involving spindle disfacilitation or Golgi afferent modulation.