Wobble board instability enhances proactive postural control

Rehabilitating a stable, upright posture requires tailoring therapeutic training to the multiscale dynamics of postural control. Wobble board training offers a unique approach to postural rehabilitation by fostering safe, shorter-scale variability, scaffolding an individual's exploration of longer-scale multijoint coordination between the center of mass (CoM) situated within the midsection of the standing body and the postural center of pressure (CoP) located on the support surface. We tested 48 healthy young adults standing on a wobble board, inducing mediolateral (ML) instability, to examine how wobble board training influences multijoint coordination. Detrended Moving Average (DMA) analysis of CoM and CoP fluctuations yielded fluctuation functions showing that wobble board training caused CoM and CoP variability to diverge at shorter timescales and converge at longer timescales. Specifically, crossovers along the anteroposterior (AP) axis fluctuations occurred later for CoM fluctuations and earlier for CoP fluctuations, suggesting that reflex activity persists over longer timescales for CoM fluctuations in the AP direction, whereas CoP fluctuations showed the reverse, that is, the extension of longer-timescale intentional resetting of equilibrium. Wobble board training reduced temporal correlations for CoM fluctuations while enhancing them for CoP fluctuations without compromising shorter-scale temporal correlations, even during a secondary visual search task. So, wobble board training promotes robust postural control strategies, shifting control from CoM to CoP into proactive, AP-oriented variability-an approach that could help tailor wobble board training to individualize postural rehabilitation. Multiscale modeling of posture thus advances understanding of the physical-therapeutic application of wobble boards to posture, amounting to effective rehabilitative training of CoP response to CoM excursion.