Influence Of Resistance Training On Strength And Gait Kinetics In Individuals With Acl Reconstruction

Abstract

PURPOSE: Individuals with anterior cruciate ligament reconstruction (ACLR) demonstrate reduced hip and knee extensor strength in their injured limb. Previous research suggests strength imbalances reduce an individuals’ ability to propel themselves forward during gait as indicated by the impulse of the anterior ground reaction force (propulsive force; pGRF). As resistance training increases muscular strength, it may improve any propulsion deficits. Therefore, the purpose of this study was to compare hip and knee extensor strength as well as pGRF characteristics between individuals with ACLR who resistance train (RT) and ones who do not (NRT). METHODS: Hip and knee extensor strength and gait were measured in 16 individuals (22.4±4.2 yr, 1.7±0.1 m, 73.8±15.1kg) with unilateral ACLR via isokinetic dynamometry and force platforms, respectively. The RT group had individuals who resistance trained according to the American College of Sports Medicine guidelines consistently after completion of physical therapy. The NRT group included individuals who did not resistance train at all. Independent samples T-tests were used to compare peak hip and knee extensor strength (Nm/kg-1), peak pGRF (N/kg-1), and pGRF impulse (N•s/kg-1) between the RT and NRT groups. Bivariate correlations were used to identify if hip and knee extensor strength were related to pGRF and pGRF impulse. RESULTS: The RT group had greater peak knee extensor torque at 60o/sec-1 (KE60) and 180o/sec-1 (KE180) compared to the NRT group. No differences were observed between groups in peak hip torque, pGRF, or pGRF impulse. There was a negative correlation between KE60 and pGRF during walking (r = -0.531, p=0.034). No correlations were found between pGRF impulse and hip or knee torque. CONCLUSION: Results confirm our hypothesis that in ACLR, individuals in the RT group exhibited greater knee extensor torque than the NRT group. Additionally, greater KE60 was related to less pGRF during walking. An exploratory analysis found no differences in walking or running velocities, indicating the RT group accomplishes the same goal with less force. This may demonstrate greater movement efficiency resulting from resistance training above the improvements in strength alone.