“…Previous studies have evaluated the squat, leg press and knee extension [13], the squat and leg press [14], variations of the squat and the lunge [34], as well as combinations of rehabilitation exercises [3,18,21]. However, a number of studies that assessed the quadriceps muscle group activation during resistance training exercises used low loads, body weight only, the same load for all exercises, or did not normalize the EMG to maximum voluntary isometric contraction (MVIC), thus limiting the significance of these studies or making it difficult to compare the results to other research [3,5,12,21,23,31,34]. At present, no source has evaluated a large number of exercises that incorporate knee extension, for the purpose of comparing activation of the quadriceps and hamstring muscles groups, their activation ratios, and gender differences therein.…”