The quadriceps are the four muscles that make up the front of the thigh, the rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis. They are powerful extensors of the knee and the rectus femoris muscle is also engaged in flexing the hip. The vastus medialis located on the medial side of the legs inner thigh just above the patella or kneecap, helps extend the lower leg and stabilize the patella. The medialis is particularly important in keeping the kneecap tracking correctly during movement.

A common exercise to isolate the vastus medialis used by  athletic trainers and coaches is called the ‘short-arc’, a motion which takes advantage of the muscle being more active in the last 15 degrees of movement. Studies have shown over 50% more electrical activity in the vastus medialis as it moves in this 15-0 range of motion to obtain full knee extension.

The short-arc is an important exercise tool following a leg injury as the vastus atrophies noticeably and quickly. Strength training emphasizing these last degrees of motion hastens recovery and enhances knee stability.

To perform the short-arc on the Pendulum Leg Extension adjust the range limiter from the bottom slot and move it upwards to its highest point.

Beginning to Adjust the Range Limiter to Highest Position

Once the limiter is in the highest position the exercise can be used to target the medial quadriceps for rehabilitation or for what is deemed ‘prehab’, a movement to help prevent an injury or to prepare a person who might be having surgery to help speed recovery post operation.

Single Leg Short-Arc