Effects of motor inhibitory control during voluntary gait initiation in young and older adults

BACKGROUND AND AIM: Age-related changes in inhibitory control (IC) are associated with reduced gait adaptability, balance recovery and an increased fall risk. However, since most studies of IC during motor tasks focus on upper extremity tasks (e.g. Stop signal tasks), it is unclear how IC may directly affect balance performance. A recent scoping review of studies investigating balance performance on tasks requiring IC, demonstrated that the few available studies show a large heterogeneity of task conditions and outcome measures and that not much attention has been given to motor inhibition; i.e. the ability to suppress an incorrect motor action. Therefore, we designed a novel gait initiation task which requires a person to block gait initiation in response to a stop signal. Our study aims to determine how different latencies of the stop signal affect voluntary inhibition of gait initiation and balance in young (YA) and healthy older adults (OA). METHODS: Participants (23 YA and 45 OA) were instructed to initiate gait promptly when presented with a "Go" signal (a green light). In some of the gait trials, a "Go" signal was followed by a "Stop" signal (red light) which required the person to immediately block gait initiation and remain standing. The gait initiation task comprised 3 blocks, each consisting of 9 Go and 3 Stop trials. Randomized stop signals were presented with three different delays, and after data-acquisition, the exact timing of a stop signal was determined in relation to onset of gait initiation (i.e. onset of a posterior shift in CoP). Data analyses focused on Stop trials and comprised changes in Centre of Pressure (CoP) position (as measured by a Bertec force plate (1000 Hz)), as well as changes in foot position, success of blocking gait initiation, and the Margin of Stability (MoS) (as measured by a Qualisys motion capture system (100 Hz)). RESULTS: The state of gait initiation at a stop signal depended on the latency of the Back to the contents page stop signal after onset of gait initiation. Thus, different delays of stop signals presented a person with different degrees of difficulty of blocking gait initiation. In YA as well as in OA, success of blocking gait initiation depended on latency and magnitude of the posterior CoP shift. Results show that CoP variables as well as success rate were significantly affected by age. CONCLUSIONS: This novel method to study motor inhibition during voluntary gait initiation demonstrates that task difficulty, and hence success rate, depend on the timing of Stop signals after onset of gait initiation and that success rate is lower in OA compared to YA. The method addresses an important aspect of mobility in daily life and provides a base for further studies
of age-related changes in IC and balance.