Effects of asymmetric load carrying on the biomechanics of walking

The purpose of the study was to investigate the effects of an asymmetric sidepack carrying system on frontal plane joint moments of force in both lower extremities and in the L5/S1 joint during level walking. Ground reaction force data and frontal plane film records were obtained from five males performing three walking conditions: 0, 10 and 20% bodyweight loads in a sidepack supported by the left shoulder. Inverse dynamics were used to calculate the lower extremity moments during stance and a static model of the pelvis was used to calculate the L5/S1 moments during single support for each limb. Normal walking was characterized by symmetric kinetics between left and right limbs and around the L5/S1 joint. The asymmetric loads produced unbalanced lateral trunk muscle dominance between left and right limb stance phases, increased right hip and knee moments and decreased left hip and knee moments. During normal walking, the L5/S1 moment was dominant on the contralateral trunk side for both limbs. The asymmetric loads applied to the left side caused a shift in L5/S1 moment dominance to the right side during left and right single support phases.