In previous articles I’ve discussed several of the common strength and mobility problems that cause of overpronation. Some of the major factors covered up to this point have include weak foot musculature, limited dorsiflexion range of motion, and anterior pelvic tilting. This post addresses the role of inversion and eversion strength in controlling pronation.
Ankle inversion and eversion are motions that come primarily from the subtalar joint–the joint between the calcaneus (heel bone) and the talus bone. Inversion can be seen when you point the sole of your foot towards the opposite foot without moving the rest of your leg. Eversion is the opposite motion as inversion.
When the foot is in contact with the ground, too much eversion contributes to overpronation.
In order to prevent this excessive pronation the anterior and posterior tibialis muscles have to be strong enough resist the eversion forces to pull the foot into inversion. Weakness and degeneration of the posterior tibialis is known to be one of the main causes of flat foot deformity in older adults.
One study found that strengthening both inversion and eversion was able to reduce the amount of pronation in runners. The study split 22 runners with excessive pronation into two groups. The experimental group performed isokinetic inversion and eversion exercises 3 times a week for 8 weeks. The control group did exercises “commonly used in ankle rehabilitation”.
The group performing the inversion and eversion strengthening exercises showed a marked decrease in their pronation measurements.
Even though the size of the study was small and the researchers used isokinetic exercises (expensive variable resistance machine required) the results should be encouraging to anyone looking to correct their pronation problems. The easiest way to do inversion and eversion strengthening at home is to use exercise bands for resistance.
I’ll usually aim for 3 sets of 20 to 30 reps. Starting with the band in a more stretched position increases the resistance no matter what strength band you are using.
The other variable that can easily be modified is the positioning of the exercise. To get the most benefit these should be done both with the leg extended (as in the pictures) and sitting on a chair with the knee bent. Bending the knee alters the way the muscles are recruited.
A full description of the resistance band exercises can be found here.
For anyone curious this is what isokinetic inversion and eversion strengthening looks like: (Video). The isokinetic machines are usually found in rehab clinics. They’re nice because they provide variable resistance and are relatively safer than free weights.
The disadvantages, other than the cost of the equipment, are the fixed range of motion set by the machine and the isolation of the joint being exercises, meaning stabilizing muscles outside of that joint are not getting strengthened at the same time. Unless you have access to one at the gym, it’s probably not worth spending $50, 000 just to do some ankle strengthening. Exercise bands can be found at most sporting good stores and come in handy for a lot of other exercises.