The Powered Simplest Walking Model Modifies the Rate of Recovery Definition

Abstract

AbstractHumans aim to minimize their walking energy expenditure. As walking mechanical work demands a metabolic cost, minimizing mechanical work performance may limit the metabolic cost of walking. As such, it is suggested that humans conserve a portion of each step’s mechanical energy, transferring it to the next step, known as the rate of recovery. Previous definitions assumed human walking to be conservative as an inverted pendulum, requiring extra mechanical energy infusion when potential to kinetic energy conversion was upset. However, as human walking grossly deviates from pendular motion during step-to-step transitions, we proposed a new definition based on mechanical energy dissipation of each transition. Analytical simulation depicted rates of recovery exceeding 80%, with rates over 50% for young adults with normal lookahead based on the experimental data, surpassing previous suggestions. Both analytical and experimental results showed declining trends with velocity, indicating the new definition did not designate preferred walking speeds. Simulation also revealed that reducing pre-emptive push-off magnitude aligned with declined rates of recovery. Reversing the preferred order of push-off and collision almost halved the rate of recovery. Experimental results demonstrated that age, restricted lookahead, and terrain complexity (amplitude increase) lowered the rate of recovery, consistent with prior reports of increased energetics cost of walking under these conditions.