 This is based on the relationship that equates step width to formula_4, where formula_5 is leg length.Step variability is a measure of the standard deviation of step length and step width calculated from all valid steps during a single walking trial.At self-selected walking speeds, step width variability (~2.8 cm) is almost always greater than step length variability (~1.8 cm)

In dynamic walking, the human body can be modeled as the center of mass (COM) supported by a massless rigid leg in single support and two massless legs during double-support, which is consistent with passive dynamics of the inverted pendulum, otherwise known as the inverted pendulum theory of gait.