Fixed and self-paced treadmill walking for able-bodied and transtibial amputees in a multi-terrain virtual environment

•Walking speed varied in a multi-terrain virtual environment (CAREN-Extended).•Greatest speed changes for uphill, hilly, and downhill walking (self-paced mode).•Outcome measures were similar with treadmill speed as a covariate.•For self-paced, participants adopted a different step strategy uphill compared to fixed-pace.

A self-paced treadmill automatically adjusts speed in real-time to match the user's walking speed, potentially enabling more natural gait than fixed-speed treadmills. This research examined walking speed changes for able-bodied and transtibial amputee populations on a self-paced treadmill in a multi-terrain virtual environment and examined gait differences between fixed and self-paced treadmill speed conditions.Twelve able-bodied (AB) individuals and 12 individuals with unilateral transtibial amputation (TT) walked in a park-like virtual environment with level, slopes, and simulated uneven terrain scenarios. Temporal-spatial and range-of-motion parameters were analyzed.Within the self-paced condition, all participants significantly varied walking speed (p < 0.001) across different walking activities. Compared to level walking, participants reduced speed for uphill and hilly activities (p < 0.001). TT also reduced speed downhill (p < 0.001). Generally, differences in temporal-spatial and range-of-motion parameters between fixed and self-paced speed conditions were no longer significantly different with a speed covariate. However, for uphill walking, both groups decreased stride length during self-paced trials, and increased stride length during fixed-speed trials to maintain the constant speed (p < 0.01).The results from this study demonstrated self-paced treadmill mode is important for virtual reality systems with multiple movement scenarios in order to elicit more natural gait across various terrain. Fixed-speed treadmills may induce gait compensations to maintain the fixed speed.