Central set influences on gait. Age-dependent effects of postural threat.

We tested the hypothesis that anxiety regarding the potential consequences of a possible fall would alter gait patterns differently between younger and older adults. Sixteen younger and fifteen older adults participated in this study. Participants walked at a self-determined velocity along a 7.2-m walkway under 4 different conditions of postural threat; the walking conditions varied depending on the width constraints of the walkway (0.60 m vs 0.15 m) and the height of the walking surface (floor vs elevated: 0 m vs 0.60 m). Results indicated that although both younger and older adults altered their gait patterns under conditions of increased postural threat, the movement adaptations observed among older adults were substantially different to those adopted by younger adults. These age-dependent differences were strongly evidenced in the joint kinematics and the variability of the gait pattern within each condition. Our findings also indicated that when postural threat increased, the level of muscle activation throughout the gait cycle was altered in the distal musculature (gastrocnemius m. and tibialis anterior m.) among older adults only. Based on the age-related differences observed, we believe that the gait pattern alterations observed among younger and older adults reflect central set modifications to postural control that are mediated by a heightened anxiety imposed by the constraints of the testing conditions. Based on the age-dependent differences in the observed gait pattern modifications, it appears that the effects of anxiety on the control of locomotion are more pervasive for older adults than for younger adults.