Article

Adaptation is essential in maintaining stability during balance-challenging
situations. We studied, in standing subjects with eyes open and closed, adaptive
responses of the anteroposterior head, shoulder, hip and knee movements ; gastrocnemius and tibialis anterior EMG activity and anteroposterior body posture
when proprioceptive information from the neck or calf muscles underwent vibratory
perturbations. After 30s of quiet stance, vibratory stimuli were applied
repeatedly for 200s, and adaption to stimulation was analyzed in four successive
50s periods. Repeated neck and calf vibration significantly increased linear body
movement variance at all recorded sites (p<0.001, except neck stimulation with
eyes closed, EC-neck), increased tibialis anterior (p<0.001, except EC-neck) and
gastrocnemious muscle activity (p<0.001). Most body movement variances and
tibialis anterior EMG activity decreased significantly over time (most
p-values<0.01 or lower) and overall, the body leaning forward increased from 5.5
degrees to 6.5 degrees (p<0.01). The characteristics of the responses were
influenced by vision and site of vibration, e.g., neck vibration affected body
posture more rapidly than calf vibration. Our findings support the notion that
proprioceptive perturbations have different effects in terms of nature, degree
and adaptive response depending on site of vibratory proprioceptive stimulation,
a factor that needs consideration in clinical investigations and design of rehabilitation programs.

Langue : ANGLAIS