An Electromyographic Analysis of Quadriceps Femoris Muscle Setting and Straight Leg Raising

Physical therapists routinely advise patients to perform quadriceps femoris muscle setting or straight leg raising or both following knee surgery or trauma from knee injury. Little information exists, however, about the intensity of effort required from knee and hip musculature during the exercises. This study was designed to compare the level of electromyographic activity during maximally resisted straight leg raises with the level during quadriceps femoris muscle setting exercises for the vastus medialis, rectus femoris, gluteus medius, and biceps femoris muscles. Forty healthy young adult men and women performed randomly ordered trials of each exercise in the supine position. Electromyographic activity was recorded from surface electrodes and normalized to values derived from maximal isometric trials. Statistical analysis demonstrated significantly greater (p < .0001) vastus medialis, biceps femoris, and gluteus medius muscle activity during quadriceps femoris muscle setting. The rectus femoris muscle was significantly more active (p < .0001) during the straight leg raise. The study demonstrated remarkably different muscle activation levels between the exercises studied and clearly indicates that selection of the exercises needs to be based on the therapeutic objectives.