Lumbopelvic moments are key contributors to lower limb forward acceleration and deceleration in male runners

Lumbopelvic moments may affect the lower-limb accelerations and decelerations that contribute to the limb forward displacement during running. We investigated the lower-limb anteroposterior accelerations induced by axial and sagittal lumbopelvic and sagittal lower-limb joint moments during limb forward acceleration (late stance and early swing) and limb deceleration (late swing) at different running speeds. Subject-specific simulations were performed using kinematic and kinetic data for ten healthy male runners during treadmill running at speeds of 2, 3, 4, and 5 m/s. The anteroposterior accelerations of the lower-limb mass center induced by the lumbopelvic, hip, knee, and ankle moments were estimated through induced acceleration analysis for the lower-limb segments. The contribution of each joint moment to lower-limb acceleration (during late stance and early swing) and deceleration (during late swing) was computed and compared using Analysis of Variance (α = 0.05). The contribution of the lumbopelvic axial moment to acceleration was larger than the other joints' contributions (p < 0.001) (44.1 %-54.7 % of all contributions), except for the ankle plantarflexion moment contribution in the 2, 3, and 4 m/s speeds. The mean contributions of the lumbopelvic axial and sagittal moments to deceleration were the largest (p < 0.001) (47.3 % ± 7 %; 46.3 % ± 6.6 %, respectively). The relative contributions of the lumbopelvic axial moment increased with higher running speeds, while the lumbopelvic sagittal and ankle contributions decreased. In running, the lumbopelvic axial moment is principally responsible for limb forward acceleration during late stance and first part of swing, while the lumbopelvic axial and sagittal moments are the main limb decelerators before the following foot contact.