If you've ever had to rehabilitate an ankle injury, you've more than likely done single-leg balance exercises. One purpose of these exercises is to strengthen the tendons and ligaments around the ankle joint. Another benefit of the exercises is to improve body balance and body-in-space awareness.
This proprioceptive sense is believed to be a combination of information from neurons located in the inner ear and in stretch receptors located in the joint-supporting ligaments and muscles.
Those of you who have a history of sprained ankles can use these exercises to strengthen your ankles, which can help prevent serious ankle sprains. Of course it is likely that at one time or another you'll roll an ankle; but having strong tendons and ligaments might keep an otherwise minor sprain from being a bigger problem. Single-leg balance exercises can also build strength in all of the stabilizing muscles in the lower leg, not just the ankle.
When running you land on one foot at a time and count on your body to remain upright and balanced until the other foot hits the ground. It is easy to pick out those who lack the strength and balance skills to pull this off as they often fall to the ground. For example, babies learning to walk.
After mastering basic walking and running capability, it's best if both legs are equal in strength and proprioceptive ability. Unfortunately, most of the time our strength is not balanced from right to left and we feel more balanced and steady on one side or the other.
The balance exercises below will help you determine which side is your weak side, not pulling its share of the load. I suspect there is one seemingly easy balance exercise that you cannot do right now. Check it out.
Exercise 1: Looking forward, stand on one foot and count 1001, 1002, 1003, 1004, 1005. The non-weight-bearing foot can be anywhere, but it's easier to begin with it close to the ground. Switch which foot is weight-bearing and repeat the same count. Repeat the set (right leg and left leg) some five to 10 times. As you progress, build up to a 30-second count per foot. As you increase the time per foot, you can decrease the number of sets.
Exercise 2: Looking forward, stand on one foot and count to five. Remain on that foot, look over your right shoulder and count to five. Remaining on that foot, look over your left shoulder and count to five. (The weight-bearing foot gets a total count of 15 before resting.) Switch feet. Repeat each foot five to 10 times.