Minimal running? Focus on the Achilles Tendon 11/20/12
If you are thinking of transitioning to a minimal shoe, or want to incorporate some barefoot training into your running routine, focusing on the Achilles tendon can help prevent pain and injury from occurring. Why is the Achilles tendon so much more of a focus of a minimal runner vs. someone wearing a traditional shoe? A traditional shoe has a 12mm difference from the heel to the toe (drop) and a minimal shoe has a 4mm drop (or a zero drop depending on how minimal you go). This decreased heel to toe drop places additional strain on the Achilles tendon. If it is not strong enough or flexible enough to handle this, problems can occur.
The Achilles tendon connects our calf muscles (gastrocnemius & soleus) to our heel (calcaneus). The major function of the Achilles is to plantar flex the ankle, or to point the toes. Every time we push off from the ground during our gait or running cycle, the calf muscle and Achilles tendon contract to complete this motion. What we should strive for in good form running is an average cadence of 90 steps per minute. That means that the Achilles tendon is being asked to perform 90 contractions every minute. If you are running for 30 minutes, an hour, or even 4 hours, that’s a lot of calf muscle contractions! Try this, stand on one leg and try to perform 90 heel raises in a one minute period. Make sure you perform the “down” phase of this motion slowly (I’ll explain why a little later). Most people will probably start to fatigue around 20 or 30 reps. If this this is very difficult, painful, or you are unable to do it, you should work on developing strength in this motion prior to making the transition to a minimal shoe.
In addition to strengthening the Achilles tendon, making sure that the tendon is flexible enough to handle the lower heel to toe drop of a minimal shoe is very important. When our foot strikes the ground in a minimal shoe, even if we initially strike in a more mid-foot position, our heel still has to lower to the ground at some point. A traditional shoe cushions the heel and keeps it from dropping too far to the ground. A minimal shoe allows the heel to drop towards the ground an additional 8mm more than a traditional shoe. Does 8mm really make that much of a difference? The biggest reason why this increase in range of motion makes such a big difference in terms of Achilles strain is because it causes the Achilles tendon to contract “eccentrically” through the available range of motion. An eccentric contraction is a muscle contraction that produces force while the tissues of the muscle and tendon are simultaneously lengthening. Eccentric contractions cause the most damage to tissue, but they also provide the greatest gain in strength. If you have ever had a hard run, then couldn’t walk down stairs for a few days after, you have experienced the result of eccentric contractions of the quad muscles! Causing the Achilles tendon to eccentrically contract for an extra 8mm will create damage to the tissue. This damage is ok, as long as we allow it to heal appropriately and maintain flexibility of the calf and Achilles to accommodate for the increased available range of motion that a minimal shoe gives us. This is why it is so important to perform the down phase of a single leg heel raise slowly, it develops eccentric strength!
Most people are used to wearing shoes all day that support the heel. This places the Achilles in a slightly shortened position, which, over time, can cause decreased flexibility. When we sleep at night, we tend to point our toes (plantar flex), which also causes the tendon to rest in a shortened state. Since many things that we do during the day contribute to calf tightness, we really need to focus on increasing flexibility. A good way to work on flexibility of the calf and Achilles is to perform an exercise called inch worms. This exercise stretches the calf muscle as it crosses the knee joint and the Achilles tendon as it crosses the ankle joint. To perform this exercise, start in a push up position. Walk your feet towards your hands, trying to keep your knee as straight as possible while keeping your heel as close to the ground as possible. So you are “inching” your feet towards your hands.
Incorporating single leg heel raises and calf stretching into your regular routine can help make your transition from a traditional shoe to a minimal shoe much more enjoyable!