Force-Controlled Balance Perturbations Associated with Falls in Older People: A Prospective Cohort Study

Balance recovery from an unpredictable postural perturbation can be a challenging task for many older people and poor recovery could contribute to their risk of falls. This study examined associations between responses to unpredictable perturbations and fall risk in older people. 242 older adults (80.064.4 years) underwent assessments of stepping responses to multi-directional force-controlled waist-pull perturbations. Participants returned monthly falls calendars for the subsequent 12 months. Future falls were associated with lower force thresholds for stepping in the posterior and lateral but not anterior directions. Those with lower posterior force thresholds for stepping were 68% more likely to fall at home than those with higher force thresholds for stepping. These results suggest that amount of force that can be withstood following an unpredictable balance perturbation predicts future falls in community-dwelling older adults. Perturbations in the posterior direction best discriminated between future fallers and non-fallers

The body configuration at step contact critically determines the successfulness of balance recovery in response to large backward perturbations

Item does not contain fulltextThe mechanical efficiency of stepping to recover balance can be expressed by a biomechanical model that includes the trunk inclination angle and the angle of the leg at the instant of stepping-foot contact. The aim of the present study was to test the hypothesis that this model would accurately predict the successfulness of recovery attempts (recovery vs. falls) following large backward perturbations. Ten young participants were exposed to a series of 12 very large postural perturbations in the backward direction by means of a support-surface translation. At the instant of stepping-foot contact, we calculated the trunk inclination angle and the angle of the stepping leg with the vertical. Reaction time, step duration, step velocity and step length were also determined. A logistic regression analysis revealed that the model with leg and trunk inclination angles accurately predicted successful recovery, with a more forward tilted trunk and a further backward positioned leg increasing the probability of success. The set of spatiotemporal step variables was significantly less predictive. Over the course of the experiment, participants gradually became more successful in recovering balance, which coincided with an increase in leg but not in trunk angles. In conclusion, the body configuration at the instant of first stepping-foot contact accurately predicted successful balance recovery after a backward postural perturbation. Given the observation that participants improved their performance by increasing their leg angles, which suggests that it may be easier to improve this variable, compared to the trunk angle, by exercise interventions