Lower extremity muscle activation patterns during running in individuals with and without anterior cruciate ligament...

Prior post-anterior cruciate ligament reconstruction (ACLR) running studies have primarily examined discrete amplitude outcomes of electromyographic signals during short running protocols. This study conducted a comprehensive examination of both amplitude and frequency characteristics across the entire electromyographic signals from lower extremity muscles between individuals with and without ACLR during a 30-min run.

Twenty individuals with ACLR and 20 matched healthy controls participated. Electromyography data of the rectus femoris (RF), vastus medialis (VM), semitendinosus (ST), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (MG) during the stance phase were compared between groups (ACLR vs. healthy controls) over time (5th vs. 25th min of running) using functional linear models and frequency analysis with principal component (PC) analysis.

Compared to healthy controls, individuals with ACLR exhibited higher amplitudes in VM, ST, BF, TA, and MG during the late-stance phase but lower amplitudes in all muscles at the early- to mid-stance (all p < 0.05). From the 5th to 25th min, amplitude increased in all muscles but decreased in RF and BF in specific stance regions (all p < 0.05). PC scores for RF, VM, and MG were lower in individuals with ACLR than in controls (all p < 0.05). PC score of ST was lower at the 25th min than at the 5th min (p = 0.02).

Individuals with ACLR exhibited lower amplitudes in lower extremity muscles during the early- to mid-stance phase, higher amplitudes during the late-stance phase, and a shift toward recruiting slower frequency contents in the quadriceps and MG.