Prolonged neck proprioceptive vibratory stimulation prevents the self-motion misperception induced by neck muscle fatigue: immediate and sustained effects.

A recent study has shown that fatigue of the posterior neck muscles, induced by prolonged isometric contractions, causes self-motion misperception. The present study investigates whether focal vibration of the posterior neck muscles can prevent or abolish it. Self-motion perception was assessed by analyzing the tracking of a ground-fixed visual target during passive sinusoidal horizontal trunk rotation, both symmetric and asymmetric, with a stationary head. After prolonged isometric contractions that induced posterior neck muscle fatigue, perceptual responses to symmetric sinusoidal trunk rotation showed a decrease in gain at lower rotation velocities, and an increase in the final position error (FPE). The changes in gain and FPE were completely prevented by prior high-frequency vibration (100 Hz for 3 min) of the posterior neck muscles, whereas they were eliminated when the vibration was applied after the fatigue-induced deficit had already occurred. We suggest that the focal vibration activating the neck muscle proprioception may inhibit fatigue signals, possibly through a gate control mechanism. Furthermore, the persistence of the vibratory effects was examined by testing the perceptual gain and the FPE after prolonged vibratory application (three separate sessions of ten minutes each, at 1 min rest intervals). It was found that the effects of fatigue on the FPE was eliminated even one week after vibration. This finding suggests that the focal vibratory procedure may be useful to attenuate the impact of fatigue on self-motion perception, potentially preventing deterioration of balance and orientation abilities.