Step frequency in walking

Increasing the step length and decreasing the step frequency at a given speed of walking requires a greater power to lift and accelerate the centre of mass of the body (\u1e86(ext)), whereas decreasing the step length and increasing the step frequency requires a greater power to accelerate the limbs relative to the centre of mass (\u1e86(int)). The sum \u1e86(tot) = \u1e86(ext) + \u1e86(int) reaches a minimum at a step frequency which is 20%-30% less than that freely chosen during walking at that speed. The step frequency at which \u1e86(tot) is minimum increases with speed similarly to the natural step frequency during normal walking