Effect of virtual reality environment complexity on tolerance and locomotor performance in individuals with lower-limb amputation

Among emerging gait rehabilitation approaches, virtual reality (VR) enables the simulation and control of ecologically valid environments and the reproduction of complex real-world situations. Although its effects on locomotor performance have been demonstrated in healthy individuals, it remains unclear how progressively increasing levels of virtual environment complexity influence locomotor performance in individuals with gait impairments, such as those with lower-limb amputation. The aim of this study was to investigate how varying levels of virtual environment complexity affect tolerance and locomotor performance in this population. Twenty-five individuals with lower-limb amputation performed flat and slope walking tasks under five experimental conditions: two real-world environments and three immersive VR environments with progressively increasing levels of complexity. Locomotor parameters were collected using inertial measurement units. Following each VR condition, participants completed tolerance and preference questionnaires and underwent postural stability assessments using a baropodometric platform. Tolerance rates were 96.0% (95% CI [79.6%, 99.9%]) for flat and 95.8% (95% CI [78.9%, 99.9%]) for slope walking. Confidence ellipse area increased only for simple immersion after slope walking (+ 132 mm², p = 0.024), while CoP length increased in laboratory (+ 37 mm, p = 0.004) and complex (+ 119 mm, p < 0.001) immersions. VR reduced walking speed and stride length, particularly in the complex environment. Healthy-side foot clearance increased during flat walking in simple (+ 0.53 cm, p = 0.003) and complex (+ 0.31 cm, p < 0.001) immersions, while circumduction decreased during uphill and downhill walking on both sides ( p < 0.050) and on the healthy side during flat walking ( p < 0.001). These findings support the feasibility, safety, and potential clinical relevance of VR-based gait rehabilitation for individuals with lower-limb amputation. VR immersion induced specific gait adaptations, including increased sound-side foot clearance and reduced circumduction, while greater environmental complexity further altered walking speed, stride length, and postural control. These findings suggest that modulating virtual environment complexity may provide a valuable tool for tailoring rehabilitation interventions.