Effect of neck muscles and gluteus medius vibrations on standing balance in healthy subjects

Introduction Muscle vibration can be used to improve the center of pressure (CoP) shift. Several muscle sites have been used for various diseases without that we know their respective interest. Objective To compare the effects and post-effects of neck muscle vibrations (NMV) and gluteus medius vibrations (GMV) on balance in healthy subjects Methods Thirteen healthy subjects, mean: 23 years, right handed were tested on posturography, closed eyes, in standing position. They received successively left NMV and right GMV in a randomized order. The variation of the deviation of CoP on the mediolateral plane was evaluated under vibration stimulation (5 min), at the end of the vibration and 5 minutes after. Results GMV induce a CoP movement to left side (9 responders) (mean: 5.21 mm; SD: 4.79; P = 0.003). At the end of the vibration, the effect remained significant (mean: 4.73, SD: 4.02; P = 0.001) and after 5 minutes, the subjects restored their initial balance (mean: 1.25, SD: 6.82; P = 0.33). For NMV, a movement toward left side was observed only in 5 subjects but this deviation seemed to be maintained at 5 min. The CoP deviation was not significant during (P = 1), immediately after (P = 0.72), and after 5 minutes of NMV (P = 0.89). Discussion GMV cause a lateral shift in 70% of the subjects of nearly 5 mm. The effect of NMV was lower and less constant (only 5 responders) but sustainable. This could be explained by a sensorimotor peripheral action for GMV while NMV would involve high level body representation in space.