Adaptation of multi-segmented body movements during vibratory proprioceptive and galvanic vestibular stimulation

Control of orthograde posture and use of adaptive adjustments constitutes essential topics of human movement control, both in maintenance of static posture and in ensuring body stability during locomotion. The objective was to investigate, in twelve normal subjects, how head, shoulder, hip and knee movements and torques induced towards the support surface were affected by vibratory proprioceptive and galvanic vestibular stimulation, and to investigate whether movement pattern, body posture and movement coordination were changed over time. Our findings suggest that the adaptive process to enhance stability involves both alteration of the multi-segmented movement pattern and alteration of body posture. The magnitude of the vibratory stimulation intensity had a prominent influence on the evoked multi-segmented movement pattern. The trial conditions also influenced whether the posture were altered and if these posture adjustments were done directly at stimulation onset or gradually over a longer period. Moreover, the correlation values showed that the subjects, primarily during trials with vibratory stimulation alone, significantly increased the body movement coordination at stimulation onset and maintained this movement pattern throughout the stimulation period. Furthermore, when exposed to balance perturbations the test subjects synchronized significantly the head and torso movements in anteroposterior direction during all trial conditions.