Changes in lower limb muscle activity after fatigue protocols during a side cutting movement in subjects with functional instability of the ankle joint

This study explored muscle activity changes in the proximal lower limbs following fatigue during side cutting movements in 20 individuals with chronic ankle instability (CAI) compared to 20 healthy controls. Electromyography (EMG) data for the Vastus Medialis (VM), Vastus Lateralis (VL), Semitendinosus (SM), and Biceps Femoris (BF) were recorded during walking and running side cutting before and after inducing fatigue. Maximal voluntary contraction (MVC) tests determined maximal torque and EMG values. Results in walking and running side cutting showed significant increases in muscle activation in the VM, VL, SM, and BF muscles in individuals with CAI post-fatigue, whereas the control group exhibited nonsignificant changes. This increased muscle activation in the CAI group likely serves as a protective mechanism to stabilize the ankles and prevent further sprains, especially during fatigued states. This study for understanding these patterns highlights the importance of designing rehabilitation programs for individuals with chronic ankle instability (CAI). These programs should focus not only on the ankle but also on the proximal lower limb muscles to improve stability and reduce the risk of future injuries.