Adequate ankle strength is necessary for stability, which allows normal movement patterns. Regaining this strength is also thought to be important for preventing future ligamentous injuries.
Some studies have shown eversion- (pushing foot outward, away from midline) to-inversion (bringing your foot inward, towards midline) strength ratios are often different in subjects with ankle instability when compared to subjects without a history of ankle injuries. While there is some contradicting evidence on which side is often impaired post ankle sprain, it seems like the majority of evidence suggests an emphasis on strengthening the ankle-evertor muscles such as the peroneals (which are plantarflexors and evertors of the ankle joint), as weakness here has lead to recurrence of ankle sprains.
The peroneals are weak after an ankle sprain because the mechanism of injury into inversion induces overstretching of the passive structures such ligaments as well as the active structures such as muscles (e.g. the peroneals – the muscles on the lateral side of your lower leg). When these muscles get overstretched—just like any other structure—they become weakened.
Both exercises shown here demonstrate non-weight bearing positions to strengthen the peroneals.
The second exercise will bias the peroneals more due to the active plantarflexion component of the ankle during the eversion.
Note: Eversion strength has also been shown to help support/stabilize the ankle.
Note: It has been shown to be more effective when these exercises are performed with clinician assisted manual resistance. This is because some individuals will be able to perform 100 repetitions and still not feel fatigue in the targeted muscle.
Citations: -“Invertor vs. evertor peak torque and power deficiencies associated with lateral ankle ligament injury” by: Wilkerson et al.
-A Prospective study of ankle injury risk factors” by: Baumhaeuer et al. -“Rehabilitation of ligamentous ankle injuries: a review of recent studies.” Zoch et al.