This model describes stance as a pendulum-like motion where the body pivots over the foot, conserving energy through gravity-assisted forward propulsion. Human bipedal walking is more energy-efficient than quadrupedal ape locomotion because it minimizes vertical displacement and leverages longer limbs for greater stride efficiency, reducing metabolic cost by up to 25% compared to all-fours movement.

Swing phase is modeled as a double pendulum (thigh and shank), where momentum from trunk and hip initiates the motion. Swing generation requires more relaxation than strength to allow passive dynamics and minimize muscle effort; trunk speed fluctuation is crucial as it provides the kinetic energy transfer needed for efficient leg swing without excessive hip flexor activation.

Coordinated walking involves motor neurons, spinal circuits (including CPGs), and supraspinal centers. Weight-bearing, hip extension, and repetitive stepping stimulate spinal CPGs, facilitating activity-dependent neuroplasticity essential for recovery.

Brain plasticity enables learning through synaptic strengthening and neural reorganization. Effective learning occurs with active, repetitive practice in realistic contexts with immediate feedback, varied difficulty, and high engagement; ineffective experiences include passive repetition, inconsistent feedback, or over-reliance on compensation rather than correction.

The four key skills are dynamic knee stability control in stance phase, dynamic weight shifting and balance through the gait cycle, maintenance of trunk verticality, and effortless generation of swing action. Scale practice for each from most difficult (near-normal, independent performance) down to easiest (for weakest patients, with maximum support like bodyweight unloading and guidance).