Transverse plane kinetics during treadmill walking with and without a load.
OBJECTIVE: The purpose of this experiment was to determine the effects of wearing a backpack on transverse plane upper and lower body torque. BACKGROUND: During unloaded walking the upper and lower body counter-rotate to reduce the net angular momentum of the body. There is less counter-rotation while carrying a load, suggesting a more rigid link between the upper and lower body. We predicted that load carriage would result in an increase in upper body torque. Because the upper and lower body may be more rigidly linked during load carriage, we also predicted an increase in lower body torque. METHODS: Twelve subjects (5 male, 7 female, mean age=26) walked with and without a backpack containing 40% of their body mass on a treadmill at speeds from 0.6 to 1.6 ms(-1). Kinematic data were sampled for 30 s at each speed, upper and lower body torque were calculated from angular acceleration and moment of inertia. RESULTS: Higher levels of upper and lower body torque were observed during load carriage than during unloaded walking. However, the increase in upper body torque was 225%, while upper body moment of inertia increased by 400%. CONCLUSIONS: The differences in torque between loaded and unloaded walking suggest that a goal of loaded walking is to minimize upper body torque, which may reduce the likelihood of injury. RELEVANCE: Knowledge of the effects of load carriage on upper and lower body torque, and related changes in coordination may provide insight into injury reduction mechanisms during load carriage.