Electromyographic analysis of knee rehabilitation exercises.

Many exercises are used to strengthen the knee muscles, yet limited studies that evaluate the exercises exist. The purpose of this study was to describe and compare the muscle firing patterns in five knee muscles during five rehabilitative exercises, which were presumed either to strengthen a specific muscle group or to elicit a cocontraction. During short-arc knee extension, the medial and lateral vasti were significantly more active during the last 15 degrees of extension than during other arcs (p < .05). The short-arc knee extension with hamstring cocontraction demonstrated significantly more activity in the rectus femoris, vastus medialis oblique, and vastus lateralis than the biceps femoris and semimembranosus in the final 15 degrees of extension (p < .05). With isometric knee cocontractions, no significant difference in muscle activity occurred in any of the arcs tested. During squatting, the rectus femoris, vastus medialis oblique, and vastus lateralis were significantly more active than the biceps femoris and semimembranosus during the descending, holding, and arising phases (p < .05). This information offers suggestions in selecting optimal knee rehabilitation exercises.