Muscular fatigue during exercise alters neuromuscular function. Exercise-induced muscle fatigue is thought to be a potential risk factor for athletic injuries. Few studies have examined the effects of functional exercise-induced fatigue on electromyography (EMG) amplitude (amp) during a highly demanding movement. PURPOSE: To examine EMG amp during a maximum vertical forward-lateral jump, pre and post fatigue. METHODS: Twenty-five asymptomatic subjects (24 ± 2.5 yrs, 175 ± 11 cm, 70 ± 13 kg) were recruited. EMG electrodes were placed over gluteus maximus (GX), gluteus medius (GM), vastus lateralis (VL), and medial hamstring (MH). A maximum vertical jump height (MVJH) was obtained as a baseline. A functional exercise fatigue protocol included 5-min of incremental running, 20-sec of lateral jumps, and 20 vertical lunge jumps. Subjects repeated this cycle until subjects’ RPE scale reached 17 (very hard) and the MVJH fell below 80% of their baseline. Prior to and after the fatigue protocol, subjects performed 5 maximum vertical forward-lateral jumps. Functional linear models were used to compare EMG amp mean difference before and after fatigue. Pairwise comparison functions with 95% confidence intervals (CIs) were plotted to determine significant mean difference. If the curve differences with CIs did not cross zero, then differences existed. RESULTS: Figure 1. After fatigue, GX EMG amp reduced at 0-4%, 38-53%, and 80-97% of stance. GM EMG amp reduced at 84-100% of stance. VL EMG amp reduced at 87-100% of stance. MH EMG amp reduced at 2-6%, 24-61%, and 78-100% of stance. CONCLUSIONS: A reduction in observed EMG amp may be related to movement and dynamic stability deficits of the lower-extremity. More data are needed to examine how these deficits increase an injury incidence.