The effect of step length, cadence, and walking speed on the trunk's vertical excursion

Gait analysis is useful in the evaluation and treatment of musculoskeletal and neurological disorders, and it is beneficial in the assessment of prosthetic and orthotic performance during walking. An understanding of the relationship between step length, cadence, walking speed, and vertical excursion of the trunk can help in analyzing and comparing healthy and pathological gait. Theoretical and empirical relationships between the vertical excursion and walking speed were analyzed for freely selected, constant step length, and constant cadence gaits. A rocker-based inverted pendulum model was used to derive mathematical relationships between walking speed and vertical trunk movement. The theoretical work was supported by data that was acquired from able-bodied adult male subjects walking across a range of speeds. We determined that the trunk's vertical excursion is determined only by step length and leg geometry, and not cadence. Freely selected gait is characterized by a linear relationship between the trunk's vertical excursion and walking speed. A constant cadence gait produces a quadratic relationship between vertical displacement and walking speed, while for a constant step length gait the vertical excursion was invariant with walking speed.