This is why you need to perform both inversion and eversion exercises. Simply take a resistance band and place it around your toes, gripping your foot firmly. Then, as you pull back, try moving your foot inward and then outward (pulling it to the other side). Perform three sets in each direction, 20 repetitions. You should also perform these exercises in the upward and downward directions and not just sideways. These are called dorsiflexion (when you pull your foot back while someone pulls it with a resistance band on the other side) and plantarflexion (vice versa). 3 sets of 20 repetitions are recommended. Another great ankle strengthening exercise is balance training. This is best done using a pillow to stand on one leg. Sooner or later your body will lose balance and your ankle will have to work to maintain balance. This will greatly strengthen your ankle and improve yours as well