Debunking the Myth of the Vastus Medialis

The quadriceps complex is comprised of four main muscles: the rectus femoris, the vastus intermedius, the vastus lateralis, and the vastus medialis (which seems to have become the most buzzworthy muscle of the four). The vastus medialis obliquus (commonly referred to as the VMO) is the middle “tear drop” shaped muscle of the quadriceps complex. Both personal trainers and physical therapists often blame generic knee pain on this guy being weak, but the literature just does not seem to substantiate that concept. If a doctor or physiotherapist has ever told you that you need to strengthen your vastus medialis, then he or she is spouting off outdated and false information.

I have seen many an article claiming that one can “isolate” the vastus medialis, or emphasize its activation, by raising the heels in a squat, by narrowing one’s squat stance, or by doing some wild exercises. These exercises are frequently prescribed to individuals with patellar tendinopathy, patellar tracking, or post-op ACL tear patients. While these concepts sound excellent in theory, the data has shown that those ideas are effectively no more than broscience. The vastus medialis and lateralis muscles contract together, and no amount of heel raise, hip external rotation, or close-stance squats will change that.

Do decline squats increase VMO activation?

The first exercise myth about the VMO is that raising the heels will increase its activation in the squat. While using Olympic lifting shoes or standing on a board will undoubtedly increase total quadriceps recruitment, as your torso will be more upright, the vastus medialis receives no preferential treatment. Rather, the vastus lateralis and medialis simultaneously work harder to squat when the heels are elevated. Similarly, the high bar squat is more quad-dominant than a powerlifting low-bar squat, and a front squat is the most quad-dominant of the three.

Does squat depth influence VMO activation?

When analyzing the angles at which the vastus medialis and lateralis are most active, Lee et. al. found that 90° or less of knee flexion was optimal. Essentially, deeper squats allow for greater vastus medialis and vastus lateralis contraction. Again, both muscles are being targeted in this instance, so the VMO is working harder, but so too is the vastus lateralis.

The other take home here is that if you want quads of the Gods, you can’t skimp on your depth. If you have to ask someone if you’re going low enough, you’re probably not! If mobility is an issue for you, then you should seek the advice of a qualified professional and dedicate time at the end of your sessions to improving your bottom position.

What about narrow-stance squats?

None of the research to date indicates that squatting with a narrow stance impacts the vastus medialis to a higher degree. In fact, it doesn’t appear that it changes the activation in any of the quadriceps muscles at all. I’m not quite sure where this myth arose, but it seems to be contradicted by the literature.

Squatting with your feet close together won't increase VMO activation,
but it may result in faulty mechanics and potential for hip impingement.

One study with Paoli et. al. looked at the EMG in 8 different thigh muscles, measuring activity in three different squatting widths and three different intensities (no load, 30% of 1 RM, and 70% of 1 RM). They tested both quadriceps and hamstrings muscles, and there was effectively no statistical difference in any of the muscles except for the gluteus maximus. No matter how close the lifters stances, their quadriceps muscles (vastus medialis included) were no more or less active at any intensity.

Surely foot position matters?

This is one that I have heard for years, and even believed myself for a while: trainers boast that externally rotating the feet will preferentially recruit the VMO, whereas a parallel foot position would lead to more evenly divided muscular recruitment. Unfortunately, no studies to date have confirmed this concept.

Murray et. al. tested twenty physically active adults in 4 different foot positions during a partial squat on the Power Tower machine. They found no real differences in EMG amplitude in differing levels of external/internal rotation. Similarly, Ninos and colleagues tested two varying foot positions (externally rotated and neutral) in the Olympic squat, and there was no noteworthy difference in vastus medialis activation.

The take home? If you have strong quads, you have a strong VMO.

Trainers have managed to come up with many creative circus-trick exercises for targeting the vastus medialis muscle, but while they might look exciting to try in videos, the basic foundational leg movements are all you need; squats, lunges, step-ups, and split squats will help you build strong quadriceps muscles, and, in turn, strong vastus medialis muscles. You can perform your leg extensions with your feet externally rotated all day, and you still won’t be able to isolate your medial quadriceps. Instead, just stick to those previously mentioned core movements and reap the benefits of your tree trunk legs!

Works Cited:

1. Caterisano, A., Moss, R. E., Pellinger, T. K., Woodruff, K., Lewis, V. C., Booth, W., & Khadra, T. (2002). The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. The Journal of Strength & Conditioning Research, 16(3), 428-432.
2. Dionisio, V. C., Azevedo, B. M. S., & Siqueira, D. A. (2013). Horizontal and Declined Squats in Healthy Individuals: A Study of Kinematic and Muscle Patterns. ISRN Rehabilitation, 2013. Chicago
3. Murray, N. G., Cipriani, D., O’Rand, D., & Reed-Jones, R. (2014). Effects of Foot Position during Squatting on the Quadriceps Femoris: An Electromyographic Study. International Journal of Exercise Science, 6(2).
4. Paoli, A., Marcolin, G., & Petrone, N. (2009). The effect of stance width on the electromyographical activity of eight superficial thigh muscles during back squat with different bar loads. The Journal of Strength & Conditioning Research, 23(1), 246-250.