The vastus medialis oblique is one of the four quadriceps muscles located on the front of the thigh and works to extend the knee joint. Weakness in the vastus medialis can result in an increase in knee injury, or chondromalacia. Chondromalacia is knee pain that results from inconsistent muscle fiber contractions and muscle fatigue. Extension exercises that you perform throughout their entire range of motion will help to strengthen the vastus medialis.
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Knee pain usually increases during leg extension activities when the knee is extended greater than a 20- to 30-degree angle, notes the ExRx website. Performing quadriceps exercises throughout their full range of motion will activate the vastus medialis. Muscle stimulation in the vastus medialis occurs in the last 20 degrees of the movement. Sit at the leg press machine and place both feet on the platform. Press the platform up, and release the safety. Lower the platform down as far as possible, or until your knees touch your chest. Return to starting position by extending your knees and hips. Repeat 10 to 15 times.
Single-leg leg extension is an isolation exercise that works the vastus medialis when you perform exercise through its entire range of motion. Sit at a leg extension machine and place the front of your lower leg against the pad. Adjust the knee articulation so that it is at the same axis as the knee lever fulcrum. Begin with your weaker leg first and extend your knee until your leg is straight. Squeeze at the top of the movement to contract the vastus medialis, before returning to starting position. Repeat 10 to 15 times on each leg.
The lunge is a functional exercise targeting the vastus medialis. Place your hand on the vastus medialis -- the inside of your upper thigh just above your knee -- to ensure it is contracting during the exercise. Begin in a split stance position. Bend your front knee and drop your back knee down until it almost touches the floor. Return to starting position and repeat for up 15 to 20 repetitions on each leg. Begin with your weaker leg first. If you have poor balance, stand next to a sturdy object for support during the lunge.
The vastus medialis helps stabilize the knee and is strongly engaged when you do stepups. Stand facing a bench or a step. Place one foot on the bench and step up onto the bench. Place your other leg on the bench before stepping down with the first leg. Repeat 10 times on each leg. The higher the bench, the more challenging the exercise. Stepping close to the bench targets more of the quadriceps and stepping farther away for the bench activates more of the glutes and hamstrings.