The Achilles Tendon and Running Shoes

When you replant a young sapling tree it looks weak and fragile, and it’s easy to think it needs support. But experts warn: “Staking trees that don’t need it can cause the tree to grow fewer roots and develop a weak tree base. Only stake your tree if it needs extra support, protection or help staying anchored.” Even when a tree does need some extra bolstering, you need to remove the stakes by the next growing season. “Otherwise,” says a site on tree care, “The tree will depend on the stake and won’t stand on its own.”

Reducing Load

The same principle holds true when it comes to footwear and your Achilles (or any other foot or body part, for that matter). “If our feet are hurt, immobilize them, but as we get them well, start strengthening them,” says podiatrist Ray McClanahan. “If we immobilize them, if we brace them, we’re not getting stronger. Not to say that’s not appropriate at times, but if your goal is strengthening, you have got to be moving in meaningful ways.”

Research and podiatrists agree that a shoe with a higher heel and a turned-up toe or rocker under the toe will reduce load on the Achilles tendon. And that’s good for runners who are having Achilles problems. According to running shoe lore, sparing the Achilles was the reason running shoes started having elevated heels in the first place.

So, if your Achilles are aching, a shoe with a higher heel might provide some relief. “I tell my patients that there is evidence that heel lifts and forefoot rocker shoes can reduce Achilles tendon loads and that they may be used as short-term or for some long-term options—ideally short-term,” says sports podiatrist Paul Langer.

Fellow sports podiatrist Rob Conenello thinks such pampering should almost always be short, with the emphasis shifting as quickly as possible to loading and strengthening. “When I have an athlete with achilles tendonopathy I usually refer them to a physical therapist to strengthen the tendon, usually focusing on eccentric strength,” Conenello says. “Part of the treatment process is to manipulate the drop of the shoe. Conenello educates the athlete, therapist and retailer on how to apply a gradual, progressive load to the tendon. Contrary to conventional wisdom, Conennello says, “I believe prescribing a lower drop shoe and carefully monitored strengthening could be much more beneficial than the old school philosophy of adding heel lifts and decreasing the load.”

The Perils of Excess Support

One problem with long-term reliance on higher heeled shoes is that it alters our physiology and changes the way the foot works. Research shows shoes with elevated heels shorten our calf muscles and achilles tendons. “If we shorten the muscles on the front and back of our legs,” says McClanahan, “The plantar intrinsics [muscles in the foot] are always stretched out beyond their proper length to tension relationship, and cannot contract properly, or decelerate the arch effectively during pronation.” The lack of stability leads to excess strain on the already-shortened Achilles tendon.

To correct for lack of stability, we put control devices in our shoes, which, like the stakes around saplings, eventually lead to other problems. Biomechanical researcher Benno Nigg explains, “Say you have a motion control shoe, that shoe has a high arch support and other things. Because the high arch support is there, you don’t need your foot muscles. That means these muscles deteriorate, they are basically gone.”

Losing the small muscles in your foot and ankle is problematic. As Nigg explains it, the small muscles, when active and strong, can react very quickly to balance cues, correcting you with small forces before you tip very far off center. But if they don’t act, bigger muscles have to engage, with far greater force and less efficiency. “When you don’t have small muscles strong enough, you have to do everything with the big muscles, even the small little things,” Nigg says. “Which means, if you want to stabilize, you have to use the Achilles tendon, and the Achilles tendon is not very good at that.”

Desperately Trying to Feel

Note that to engage quickly and provide balance and stability, those small muscles need to be able to sense the ground. A good running shoe lets them do that, while an overly cushioned one not only is an unstable platform itself but blocks the foot from feeling and reacting appropriately.

“Most folks are in too cushy, too much shoes,” says physical therapist and biomechanical researcher Jay Dicharry. “And that impairs proprioception with the ground, that causes poor movement patterns, that cause wacky parts control—which causes the imbalances which create the problems to begin with.”

Dicharry likens running in over-cushioned shoes like tying your shoes with 50 marshmallows taped around your fingers and hands. That said, he realizes that most are not going to go minimal. “I’m thrilled we’re moving toward a little bit firmer material and shoes that have a wider toe box,” he says. “Have to be happy with that for now.”

Splay for Stability

And what does that wider toe box have to do with Achilles health? While Langer points out that there isn’t any research directly connecting linking lack of splay and Achilles troubles, all agree that actively using the first toe is a cornerstone of foot stability, and the big toe can’t operate properly when squeezed out of line and squished with the others in a pointed toe box.

A forthcoming study in the Journal of Sports Rehabilitation shows that if you are wearing shoes that let you toes spread and interact with the ground, and you actually do splay your toes, you are better able to control your center of mass.

“When we squeeze our toes to be narrower than the balls of our feet, we create instability in the transverse plane,” McClanahan says. And that instability adds strain to the Achilles.

Playing the Field

Rather than mandating one type of shoe (that’s where minimalism as a movement went too far) the experts advise using a variety of shoes as tools for different times, even different running days. Conenello says, “I always tell my patience that monogamy is important in their personal relationships but not when it comes to shoes: They should experiment with different drops, brands and types of shoes. Variability will decrease overuse, which leads to pathology.”

Langer agrees, and cites his personal shoe use strategy: “In order to maximize the variability in my movement pattern and distribute the loads, I use different shoes and vary the terrain as much as I can. I might run in Vibrams on the trail one day and a stability shoe with custom orthotics on the road the next.” As a scientist, he won’t draw universal conclusions from a study of one subject, but he feels that this variability, plus eccentric strength training, helped him shake persistent Achilles problems that now haven’t bothered him for six years.

Both Langer and Conenello note that achilles problems typically increase with age, reinforcing the need for a variety of footwear, both for support on one end of the shoe spectrum, and for building and maintaining strength and range of motion on the other.

As you experiment with different shoes, use ones that support weaknesses and help you to run today as needed, but make sure some of your models allow your foot to strengthen its natural stability, emphasize foot movement, and promote proprioception. Don’t leave the supportive stakes in so long you can no longer stand on your own.

Nigg also suggest that one of your running footwear options be nothing. “Track and field athletes quite often train barefoot,” Nigg says. “Because in barefoot you use your muscles much more. The shoe takes over certain functions that these muscles in the foot and ankle joint should do. The muscles around the ankle should stabilize, the muscles in the foot should build the arch and shorten the plantar fascia. All these things disappear, because you don’t need them anymore; the more shoe you build the less you use those muscles. If you don’t do training barefoot, which most people don’t do, that is a problem.”