The extent to which healthy older adults rely on anticipatory control following simulated slip exposure

As the recovery from gait perturbations is coordinatively complex and error-prone, people often adopt anticipatory strategies when the perturbation is expected. These anticipatory strategies act as a first line of defence against potential balance loss. Since age-related changes in the sensory and neuromotor systems could make the recovery from external perturbations more difficult, it is important to understand how older adults implement anticipatory strategies. Therefore, we exposed healthy young (N = 10, 22 ± 1.05 yrs.) and older adults (N = 10, 64.2 ± 6.07 yrs.) to simulated slips on a treadmill with consistent properties and assessed if the reliance on anticipatory control differed between groups. Results showed that for the unperturbed steps in between perturbations, step length decreased and the backward (BW) margin of stability (MOS) increased (i.e., enhanced dynamic stability against backward loss of balance) in the leg that triggered the slip, while step lengths increased and BW MOS decreased in the contralateral leg. This induced step length and BW MOS asymmetry was significantly larger for older adults. When exposed to a series of predictable slips, healthy older adults thus rely more heavily on anticipatory control to proactively accommodate the expected backward loss of balance.