Back muscle fatigue and seated whole body vibrations: an experimental study in man.

The electromyography of the erector spinae muscles was studied in the thoracic and lumbar spines of six male subjects when seated in a forwardly bent position (20°) and whilst carrying extra weight (4 kg) on the front of the chest. The electromyographic responses were compared whilst the volunteers were: (a) seated in this position and exposed to whole body vibrations of 5 Hz and 0.2 g acceleration; (b) seated in this position without vibration exposure. Each test period lasted 5 minutes. Vibration exposure increased both the speed and the amount of the development of erector spinae fatigue.