Introduction: Neuromuscular deficits may persist after anterior cruciate ligament reconstruction (ACLR) despite restoration of mechanical stability, and these alterations may become more evident under fatigue. Whether graft type influences fatigue-related changes in EMG spectral behavior during gait remains unclear. This study investigated the effect of an acute
fatigue protocol on EMG median frequency (MF) during the swing phase of walking in individuals following ACLR with different graft types. Method: In this cross-sectional laboratory study, ۵۳ physically active men were included, including ۳۸ individuals with unilateral ACLR reconstructed using single-bundle hamstring tendon autograft (SB-HT, n=۱۲), double-bundle hamstring tendon autograft (DB-HT, n=۱۶), or allograft (n=۱۰), and ۱۵ healthy controls. Participants completed a progressive treadmill running protocol designed to induce systemic fatigue, terminated when Borg rating of perceived exertion exceeded ۱۷ for at least ۲ min or heart rate reached at least ۸۵% of age-predicted maximum. Surface EMG was recorded from TA, GC, VL, VM, RF, BF, ST, and GM during walking before and immediately after fatigue. We calculated EMGMF for gait phases, focusing on swing. A two-way mixed-model repeated-measures ANOVA tested the main effects of
fatigue and group and their interaction. Result: No significant main effects of
fatigue or group, and no fatigue×group interactions, were observed for the quadriceps (VL, RF, VM), hamstrings (BF, ST), or distal lower-leg muscles (TA, GC) during swing (all interaction p>۰.۰۵). A trend toward a group effect was observed for semitendinosus (p=۰.۰۶۵). In contrast, GM MF increased significantly following
fatigue across groups (main effect of fatigue: p=۰.۰۲۵, ηp²=۰.۱۱۱), with no significant group effect (p=۰.۴۳۷) or interaction (p=۰.۴۳۱). Conclusion: Acute
fatigue did not meaningfully alter GMMF in most lower-limb muscles during the swing phase of walking after ACLR, and these responses did not differ between graft types. The selective post-fatigue increase in GMMF suggests that hip stabilizer activity may respond to fatigue; however, further research is needed before clinical recommendations can be made.