The influence of vibration on maximal torque generation

Mechanical vibration is a stimulation that the human body must endure as part of everyday activity. The source of this vibration may vary from vehicles of transportation such as trains, automobiles, planes and even spacecraft, to tools of work such as chainsaws, hammers and grinders (5). Research into the effects of vibration on biological tissue is by no means new, with studies extending back to the mid 1960’s examining the response of human reflexes to vibratory stimulation (4). From that point, extensive work has, and is still being conducted in the fields of occupational health and safety (8) and ergonomics (15). However, it has taken until the mid 1990’s for study of the application of vibratory stimulation in strength development to begin (6). Research conducted by Bosco and colleagues (3) on vibration and strength development revealed significant improvements in power output during a leg press exercise. Conversely, an investigation conducted by Rittweger and associates (12) discovered a reduction in force output for an isometric leg extension and EMG median frequency. Further study conducted by Issurin and Tenenbaum (7) examined explosive strength while vibration was applied during a bicep curl. This study found substantial improvements in maximum power in the vicinity of 30%. Each of these investigators implied that the improvements realised were due to an increase in neuromuscular activity. However, the lack of EMG data collected, means that these inferences cannot be supported by data. Research conducted by Bosco and associates (2) also found improvements of around 13% in a bicep curl performed during vibration treatment. However, this study also noted a significant increase in electromyography-root mean square analysis (EMGRMS) during the lifts. With this added information, the suggestion of improved muscular activation gains some support from experimental data.