Achilles tendon (AT) injuries are common—upwards of 18% in runners (with a lifetime prevalence of 50%) and affects approximately 1 million athletes per year. And, the injury rate increases significantly as we get older.
Why is this tendon commonly inured? The answer is fairly simple, we put a lot of stress on the AT—it can be subjected to 8-10 times a person’s body weight during strenuous exercise. And because we put a lot of stress on it, we need to maintain the strength and flexibility of the AT at a fairly high level. Unfortunately, maintaining a high level of strength and flexibility is a problem for most people.
Strength needs to be maintained throughout the entire range of movement (approximately 70 degrees of ankle flexion). Flexibility needs to be enough to allow effortless movement through full range.
An easy way to test AT flexibility is to squat all the way down keeping feet flat (no heel lift) and knees over the toes. Normal flexibility is shown above.
Maintaining enough strength to withstand 10 times body weight is difficult—it involves jumping and sprinting exercises. Most AT injuries occur at lower stress levels, so maintaining a level of strength of 2-4 times body weight would be enough to prevent most AT injuries (for non competitive athletes).
Next month I will present exercises that will help maintain AT strength and flexibility.