Akyürek, TA, Ertan, H, and Darendeli, A. biceps femoris EMG activity during incline treadmill running and nordic hamstring task. J Strength Cond Res XX(X): 000-000, 2024-Although the Nordic hamstring exercise (NHE) is an effective method for strengthening the knee flexors, untrained individuals or intermediate level athletes may have difficulty performing it. In this study, we propose incline treadmill running as an alternative knee flexor exercise. The aim of this study was to compare the biceps femoris (BF) muscle activity (electromyography, EMG) levels between NHE and 10% grade treadmill running at 3 speeds. Nineteen recreationally active men were recruited for the study. Maximum voluntary contraction (MVC) with the knee flexors were completed. Nordic hamstring exercise and 10% grade treadmill running tasks were performed in a randomized counterbalanced order. Biceps femoris EMG activity was recorded during the measurements. Statistical significance was set to p <
0.05. We found that the peak EMG amplitude for BF was higher during the NHE (∼63% MVC) than during treadmill running at a 10% grade across low-to-moderate speeds. Increasing the running speed from 3.61 m·s-1 to 4.16 m·s-1 (∼49% MVC) raised the peak EMG amplitude by approximately 10% MVC. In addition, the variability in EMG amplitude for BF was greater during 10% grade treadmill running than during NHE. Although the peak EMG activity was greater during the NH task, it reached comparable levels when performing 10% grade treadmill running at a moderate running speed. Our results suggest that incline treadmill running can be an alternative knee flexor exercise that can be individualized by adjusting treadmill grade and speed, particularly for untrained individuals.