One of the most ubiquitous aspects of modern shoes — whether they be running shoes, dress shoes, or cowboy boots — is a feature called toe spring, in which the toe end of the shoe rises upward in a more or less pronounced curve.
This curve allows you to roll off the front of the foot more easily — and if you’ve ever tried to walk quickly in a pair of stiff hiking boots with limited toe spring, you know why it was invented.
It’s not a new invention: it’s been around for hundreds of years. And it works: The more toe spring, the less work your feet have to do. But if you want strong feet to protect you from foot injuries, toe spring might not be your friend.
That’s the finding of a study in today’s issue of Scientific Reports, a journal in the prestigious Nature family of journals.
In an effort to document exactly how toe spring affects to your feet, a team led by Freddy Sichting of Chemnitz University of Technology, Chemnitz, Germany, put 13 volunteers on treadmills and had them walk barefoot and in four different types of specially designed sandals. These sandals had curving soles that created toe-spring angles of 10, 20, 30, and 40 degrees—a range of curvature designed to mimic that found in modern shoes.
They were also designed with the same flexibility as modern running shoes, such as the Adidas Adizero or Nike Zoom Streak.
Sandals were used rather than shoes because that allowed the researchers to see the precise motion of their subjects’ feet as they walked — a process facilitated by putting reflective markers on their feet and ankles (as well as their knees)—a total of 15 in all. The researchers could then use stop-motion photography to film exactly how the various amounts of toe spring affected their subjects’ gaits, with particular attention to the motion of the metatarsophalangeal (MTP) joints at the base of their toes.
This information was then combined with data from force plates incorporated into the belt of a lab treadmill that allowed the researchers to see how hard their subjects were pushing off against the ground at each point in their strides.
From that, Sichting’s colleague Nicholas Holowka of the University at Buffalo, New York, told Podium Runner, it is possible to estimate the amount of work being done by the muscles that control the toes — an important indicator of how much the exertion is strengthening them. (The muscles involved are the ones that stiffen the toe. They lie in the sole of the feet, under the arch. To locate them in your own foot, stand barefoot, rock forward, and see what muscles you stiffen to keep from falling forward.)
What they found was that toe spring reduces the amount of work done by these muscles. And as the angle of the toe spring goes up, the less work these muscles do.
It’s not a huge difference in absolute terms, but, Holowka says, “these are very small muscles. So these difference could be important for how much you need to use [them] in each step. Add that up over the thousands of steps the average person takes in a day, over years, and you’re making your muscles do a lot less work.”
That of course, explains why shoes with large toe spring are popular: people gravitate to them because they keep the feet from tiring and are more comfortable, says Harvard University researcher Dan Lieberman (famous for his role in the book Born to Run), who was also a member of the study team.
“The toe spring reduces how much work the intrinsic foot muscles have to do to maintain stability at the MTP joint during propulsion,” Lieberman says. And the natural human tendency is to want to do work less, not more, especially with the muscles we aren’t intentionally working out.
In a race, that might be a good thing — in fact, it might be why top-level racing shoes have a lot of toe spring. The foot muscles aren’t major contributors to the body’s overall energy consumption, but at 11,000 or more strides an hour, it adds up. Not to mention that nobody wants to race on tiring feet.
But it also means that if you habitually wear shoes with a lot of toe spring, these muscles are not going to be as strong as they might be—a concern because it could predispose you toward certain types of injuries.
“Less work means the muscles won’t be as well conditioned, meaning that they may not be able to protect other tissues in the foot, like the plantar fascia, from trauma,” Holowka says.
Portland, Oregon, sports podiatrist and minimalist-footwear advocate Ray McClanahan (who was not part of the study team) agrees.
Toe spring, he says, keeps the toe-controlling muscles of the arch constantly stretched, preventing them from contracting as they otherwise would during each stride. That means they can’t do as good a job as they should at buffering stress to other parts of the underside of the foot, such as the plantar fascia.
Toe spring also perpetually contracts the tendons on the top of the foot that would normally help to elevate the toes. This too can contribute to plantar facia problems, McClanahan says.
But that’s not the only possible result. “Hammertoes are often the result of footwear with heels and toe springs,” he says. And, he adds, “the fat pad that is supposed reside under the metatarsal heads will be pulled up under the toes by toe spring, which leaves the structures under the ball of the feet predisposed to trauma and injury.”
What You Should Do
So, what’s a runner to do?
The study authors are scientists, not coaches, but there are a few obvious thoughts.
First, the research was on walkers, not runners. But that probably isn’t an issue. “We showed this for walking,” Lieberman says, “but it must also be true for running.”
One solution might be to go Hawaiian.
In Hawaii, and most eastern cultures, they want shoes to be left at the door. Inside, you go barefoot (or in socks or slippers). That’s not the same thing as running barefoot, but it’s a lot better than always wearing shoes with large toe spring.
You can also do toe exercises. These can be done most anytime (I’m doing them now, as I write). Mostly, these involve fidgeting with your toes, flexing and unflexing them, splaying them, lifting individual toes (toe yoga). After a while, it becomes something you do without thinking. But you can be more systematic about this, adding toe exercises like short foot contractions, (pulling your toes toward your heel by lifting your arch) and towel scrunches (where you use your toes to pull a towel up under your feet) to your normal routine.
You can also look for training shoes with as little toe spring as your feet happily tolerate — shoes that are flat and flexible. Note that if you’ve been wearing shoes with a lot of toe spring all your life, this is a big change, so be cautious not to make it too quickly.
“Research shows that walking and running in minimal shoes over a while (about 6 to 12 weeks) can strengthen the intrinsic foot muscles,” Sichting says.
When you race? That’s an open question. The large toe springs in top-of-the-line racing shoes are there for a reason. If you’re looking for tiny energy advantages in a race, they might help — especially if you already have strong feet.
Lieberman agrees. “Almost surely,” he says. But that wasn’t the focus of the current study. “Next study maybe?” he says.