Effect of Backpack Moment of Inertia on Transverse Plane Kinetics and Kinematics and Oxygen Consumption During Walking

摘要

The purpose of this experiment was to investigate the effects of systematically manipulating the transverse plane moment of inertia (MOI) of the upper body on upper body torque, lower body torque, the phase relationship between the upper and lower body, and oxygen consumption. It was hypothesized that increasing the MOI of the upper body would result in (1) an increase in upper body torque that would be less than predicted solely from the increase in upper body MOI, (2) a decrease in lowerbody torque, (3) a more in-phase pattern of pelvic and thoracic rotation and, (4) an increase in oxygen consumption. Elevensubjects (4 male, 7 female, mean age: yr+SE 26+2.0) walked on a treadmill at 1.3 ms-i without a load and with an adjustab1ebackpack containing a load that was 40% of their body mass. Seven backpack MOI conditions were achieved by sliding two metalplates along a metal bar away from the transverse plane trunk axis of rotation. In the backpack condition with the smallestMOl, the predicted upper body torque was 1.6 times greater than the actual upper body torque, while in the largest backpack MOI condition, predicted upper body torque was 2.75 times greater than the actual. Increasing the MOI of the backpack resulted in no statistically significant change in lower body torque or oxygen consumption and a significantly more out-of-phase pattern of pelvic and thoracic rotation. We concluded that increasing the MOI of the backpack increases the reluctance of the upper body to changes in rotational movement. Consequently, changes in lower body torque and trunk coordination have less influence on upper body torque, and there is a releasing of movement degrees of freedom in the lower body.