Metabolic and kinematic responses of African women headload carriers under controlled conditions of load and speed

Abstract

Recent investigations have argued for the metabolic efficiency of headloading as a mode of load-carriage, and have included proposals of an energetic 'free-ride' for loads under 20% bodymass. Our own energy-cost analyses on laboratory-habituated African women occupational headloaders is used to evaluate the free-ride hypothesis, but more especially to throw new light on the kinematics of foot-floor contact patterns. Under headloading there is a tendency for the impact-receiving mechanisms of the foot to be less effective. However, a delayed heel-rise later in the step increases stability of support by reducing the duration of forefoot-only contact. Plantar thrust under headloading has a relatively longer duration, which may have force-velocity implications for the propulsive musculature.