There’s a lot going on in runners’ feet. Each one is made up of 26 bones, 30 joints, and more than 100 muscles, tendons, and ligaments. Of those, maybe you spend a lot of time stressing about your plantar fascia. Maybe tendonitis is your literal Achilles heel. Or maybe you spend too many runs worrying about what colour your toenails will be at the end. But how much brain space do you dedicate to your big toe, specifically? We ask because it deserves your attention.

A quick anatomy lesson: Your big toe, a.k.a. the hallux, consists of two joints—the interphalangeal joint (which is up by your nail), and the metatarsophalangeal (MTP) joint, which connects the first long bone (metatarsal) in the forefoot to the first bone of the big toe (phalanx). The MTP joint is the important one for runners, because it needs to bend with every step you take—and if it isn’t doing that correctly, it could inhibit your performance.

What does the big toe do for runners?

Think about moving through the gait cycle. There are three phases: The stance phase starts when your foot hits the ground until your leg is directly under your hips; then you transfer to the drive phase, which occurs until right before your foot pushes off the ground; the swing phase refers to any time your foot is in the air.

Your big toe plays a big role in the drive phase. “One of the most important things that the big toe does when you’re running is push off the ground,” explains Patrick McEneaney, a board-certified podiatrist. “When your heel hits the ground, the pressure transfers from the lateral side—or outside—of the foot, then kind of rolls back in from the fifth metatarsal over to the first metatarsal.” During that time, energy is being stored at the first metatarsal (that long bone in the forefoot) and that energy is then utilised to push off as you go to the swing phase of your gait, he says.

The MTP joint (remember, that’s the one located at the base of the big toe) actually bears about 40 percent of your body’s weight during the stance phase of your walking gait, older research has shown. But consider this: During running, studies have determined that you hit the ground with the force of two to three times your body weight. That significantly increases the amount of force this small joint has to handle during the push-off.

Fortunately, the MTP joint works in conjunction with several other parts of the foot. “When you push off the ground, the plantar fascia becomes taut and causes the foot to act like a springboard,” explains Ricardo Cook, M.D., an orthopaedic surgeon who specialises in sports medicine and hindfoot reconstruction. “At the same time, the joints across the midpart of the foot lock and become rigid. When you push off the big toe, it flexes and transfers the weight forward.”

While your foot is on the ground, your big toe also helps stabilise the arch of the foot, says Denise Smith, a physical therapist and running technique specialist. This helps regulate the degree of foot pronation, because “a weak and unstable arch will cause runners to land or roll onto the outside of the foot,” says Smith.

“Any unnecessary motion is bad because that can cause irritability to the muscles and tendons on the outside and inside of the foot,” she explains. “Unnecessary rolling can also lead to bigger injuries, like ankle sprains or fractures, especially for those running on uneven surfaces like trails or hills.” (Overpronation, where your foot rolls too far inward, can cause issues like bunions, runner’s knee, plantar fasciitis, and Achilles tendinitis.)

In summary, the big toe’s role in running includes:

• Pushing off in the drive phase of your gait
• Transferring weight forward, providing momentum to move in that direction
• Stabilising the arch of the foot to help regulate pronation

How can you keep the big toe healthy?

In order to push off the ground, a big toe’s normal dorsiflexion (a.k.a. when your toe points upward, toward the shin) range of motion is at least 65 degrees, according to older research published in The Journal of Foot and Ankle Surgery. That range of motion is really important because “any issue with the big toe would affect your ability to generate forward motion since any transfer of momentum and force must go through the big toe joint,” says Cook.

When you don’t have a normal range of motion in your big toe, your body has to make compensations elsewhere—compensations that could lead to inefficiencies or injuries. For example, “with limited dorsiflexion, the big toe joint would have to work much harder to push off during that part of the stride,” says Cook. “The body naturally leans forward, lifts off earlier and shortens the stride to protect the joint.”

That can lead to issues because “anytime you don’t get full motion at a joint, there’s always another joint that picks up [the slack], otherwise you don’t move appropriately,” says McEneaney. In the case of the big toe, he explains, other metatarsal joints might have to absorb extra pressure; or you might supinate your foot, putting more pressure to the outside; or you might twist the midtarsal joint in pronation and use your foot and ankle to push yourself forward.

“Issues in the big toe can lead to many ‘itis’ problems—plantar fasciitis, Achilles tendonitis, posterior tibialis tendonitis,” Smith adds. “It can also cause problems up the entire kinetic chain and cause pain to develop in the buttock, hips, or low back.” Translation: Keeping this small body part healthy will pay off big time on the run.

---

How to Increase Mobility and Strength in Your Big Toe

Improving range of motion in your big toe can be as simple as bending the toe up and down and side to side, says Cook. “Like any other part of the body, stretching prior to exercise helps elongate the muscles to a functional length,” he explains. “For runners who have a problematic big toe, about a minute of stretching per big toe before every run will help loosen up the joints and muscles.”

An easy stretch any runner can do: Sit with your foot extended out in front of you and use an exercise band or even a towel to pull your big toe up towards you. “Holding that for 30 seconds and repeating 10 times twice a day can help loosen up the big toe joint,” says McEneaney.

You can also curl your toes under you while doing stretches like child’s pose or in a kneeling position.

Otherwise, “the best way to keep the big toe stretched out is to stretch the calf off of a step or in a yoga position like downward dog,” says Smith.

The flexor hallucis longus muscle, which flexes and stabilises the big toe, actually connects the base of the big toe to the back of the calf. “If you have tight calves, you can’t adequately bend or flex your foot when you run—which impacts your push-off and ability to transfer weight from the heel to the midfoot,” explains Cook.

When it comes to strength, Smith recommends two specific exercises:

READ MORE ON: big toe feet RUNNER'S FEET