Body borne loads impact walk-to-run and running biomechanics

- Joint power shifted distally down the kinetic chain with load during the walk-to-run transition.
- Load does not shift the distribution of lower limb joint power during over-ground running.
- Body borne load did not increase hip or knee flexion during over-ground running.
- Greater lower limb joint loads may impair performance during load carriage.
- Biomechanical adaptations maintain performance during dynamic locomotor activities.

The purpose of this study was to perform a biomechanics-based assessment of body borne load during the walk-to-run transition and steady-state running because historical research has limited load carriage assessment to prolonged walking. Fifteen male military personnel had trunk and lower limb biomechanics examined during these locomotor tasks with three different load configurations (light, ∼6 kg, medium, ∼20 kg, and heavy, ∼40 kg). Subject-based means of the dependent variables were submitted to repeated measures ANOVA to test the effects of load configuration. During the walk-to-run transition, the hip decreased (P = 0.001) and knee increased (P = 0.004) their contribution to joint power with the addition of load. Additionally, greater peak trunk (P = 0.001), hip (P = 0.001), and knee flexion (P < 0.001) moments and trunk flexion (P < 0.001) angle, and reduced hip (P = 0.001) and knee flexion (P = 0.001) posture were evident during the loaded walk-to-run transition. Body borne load had no significant effect (P > 0.05) on distribution of lower limb joint power during steady-state running, but increased peak trunk (P < 0.001), hip (P = 0.001), and knee (P = 0.001) flexion moments, and trunk flexion (P < 0.001) posture were evident. During the walk-to-run transition the load carrier may move joint power production distally down the kinetic chain and adopt biomechanical profiles to maintain performance of the task. The load carrier, however, may not adopt lower limb kinematic adaptations necessary to shift joint power distribution during steady-state running, despite exhibiting potentially detrimental larger lower limb joint loads. As such, further study appears needed to determine how load carriage impairs maximal locomotor performance.