Decoupling speed matters: Optimizing gait mechanics after anterior cruciate ligament reconstruction with Split-belt adaptation training of the healthy leg.

Abstract

Knee and limb underloading are common problems after anterior cruciate ligament (ACL) reconstruction associated with early-onset osteoarthritis. Split-belt treadmill training is a promising method to address knee/limb underloading, but the dose-response relationship and its efficacy to target underloading after reconstruction remain unknown. Here, we examined if split-belt treadmill training of the healthy limb (i.e., modifying belt speed under this limb) affects ACL knee/limb loading. Twenty-five participants with ACL reconstruction (Age: 23.24 ± 6.48 yr, Height: 1.73 ± 0.08 m, Mass: 76.08 ± 13.72 kg, Postoperative Time: 8.04 ± 1.78 months) were evaluated utilizing an instrumented treadmill synced with a 12-camera motion capture system. Participants completed 5 min of baseline walking with belts tied at 1.1 m/s. Belt speed under the healthy limb was then manipulated with eight, randomized 5-min decoupled speed configurations (30-170% of 1.1 m/s in 20% increments) with 2 min of tied-belt walking after each speed. Sagittal plane knee moments, angles, and vertical ground reaction forces were measured, and one-dimensional statistical parametric mapping was used to compare dependent variables between legs and decoupling speeds during stance. A dose-response relationship was found where faster speeds increased ACL knee/limb loads throughout stance and slower speeds decreased them. In the healthy limb, faster speeds led to increased early stance and decreased midstance loading, with the opposite effect at slower speeds. Our findings suggest that split-belt treadmill training of the healthy limb at faster speeds may improve ACL knee/limb loading, but further research is needed to obtain a clear understanding of how this transfers to overground walking.