Anticipatory postural control strategies related to predictive perturbations

Balance reactions can be seen as responses to sensory information on a feedback basis, but when a balance threatening situation can be predicted, an anticipatory postural control strategy can be used. This study describes characteristics of proactive postural adjustments related to repetitive rhythmic perturbations. Furthermore, the study aimed to investigate age dependency of these anticipatory strategies. Fourteen young (age 27+/-2 years) and 10 community-dwelling elderly adults (76+/-5 years) participated in this study. Centre of pressure displacement was evaluated while the participants were standing on a moveable force plate. Perturbations consisted of alternating left/right frontal plane tilts of the platform or alternating forward/backward slides in the sagittal plane. Automation of postural control was evaluated by a dual task approach after familiarization to the perturbations. Centre of pressure displacement 200 ms before a tilt perturbation was significantly related to the direction of the perturbation. This early postural adjustment was significantly increased during the dual task condition. The dual task effect was more pronounced in the elderly, but this age-effect was not significant due to large inter-individual variation. The frequency of stepping reactions as response to slide perturbations decreased with conditioning, but increased again in the elderly during dual task condition. Conclusion: This study showed that both young and elderly use anticipatory postural control strategies to minimize the impact of predictable perturbations. The proactive postural adjustments are further enhanced when a concurrent cognitive task is introduced. Postural control seems less automated in elderly and becomes insufficient during very challenging perturbations.