Change of Postural Control While Repeatedly Imposing Horizontal Floor Vibration in Upright Stance

Anticipatory postural control during arm movements and floor translation

“…Postural muscle activation improved until the fifth trial, demonstrating adaptation of postural control 27,31,33,34) . The total perturbation time in other studies of periodic floor translations with same frequency has been much lower 29,30,35) ; therefore, subjects in these studies may not have fully adapted.…”

“…However, the preceding movement which is the characteristic of anticipatory postural control is found during the floor oscillation with low frequency such as 0.1 and 0.25 Hz only on the lower legs 31,32) . During floor oscillations at frequencies higher than 0.5 Hz, the phase delay between floor oscillations and CoPap fluctuations becomes larger and close to 90 degrees 33) . It has been suggested that this change in the phase delay is caused by changes in the timing of muscle activation and then the intrinsic frequency of the body would exist around 0.5 Hz.…”

“…In the first trial, gastrocnemius and tibialis anterior were strongly activated. As the adaptation advanced with trial repetition, tibialis anterior burst activity became non-periodic or even disappeared, and activation of gastrocnemius became dominant 33,34) . Moreover, the largest activation of gastrocnemius was found around the anterior reversals and the smallest activation of gastrocnemius was observed around the posterior reversals 34) .…”