Body-weight support is the primary driver of elevated walking cost in cerebral palsy.

Background: Children with cerebral palsy (CP) exhibit substantially elevated energetic costs of walking, yet the biomechanical origins of this excessive cost remain unclear, limiting the effectiveness of current interventions. Methods: We tested the hypothesis that elevated energetic cost of walking in CP arises primarily from increased demands for body-weight support and lateral stabilization. Using a custom mechatronic system, we independently applied controlled vertical body-weight support (1-60% body weight) and mediolateral stabilization stiffness (50-1500 N/m) while children with CP and typically developing (TD) peers walked on a treadmill at a fixed nondimensional speed. We quantified steady-state energetic cost using indirect calorimetry and used linear regression models to determine energetic responses to each intervention. Results: Providing body-weight support significantly reduced net energetic cost in both groups, with a 3.5-fold greater effect in children with CP (n = 23) compared to TD peers (n = 10). Across the 1-60% support range, energetic cost decreased by 41% in CP, normalizing walking energy expenditure to TD levels. Higher baseline energetic cost of walking and greater knee flexion during stance were associated with larger energetic reductions (p < 0.01). In contrast, mediolateral stabilization produced negligible energetic effects in both CP (n = 14) and TD groups, with no demographic or biomechanical predictors of response. Conclusions: Body-weight support is the dominant contributor to elevated energetic cost of walking in children with CP, whereas lateral stabilization contributes minimally under the conditions tested. These findings identify gravitational support as a key biomechanical target for energy-focused rehabilitation and assistive technology interventions.