Flexibility in the big toe is the most important aspect of foot flexibility for runners. We should have about 70° big toe extension (aka dorsiflexion) and about 70-90° flexion (aka plantarflexion).
The big toe is the most important aspect of foot flexibility for a couple of reasons. We need good flexibility in extension (pulling the toe up) to help us activate something called the Windlass Mechanism.
The Windlass Mechanism
As the big toe extends it pulls on the plantar fascia. This tightens up the sole of the foot and actually pulls the arch of your foot upwards, creating a stable foot for you to push off from.
We can see this in action as we run. As I propel myself forwards my big toe starts to extend. This pulls the plantar fascia tight and lifts the arch up.
If we take the lines off and zoom in, you can actually see my plantar fascia all stretched taught to help support the arch, cool eh?
Lacking this extension flexibility in your big toe is a problem for runners. If your toe can’t extend then you won’t be able to make use of the windlass mechanism in order to help you stabilize the arch of your foot. This can make life very difficult for other parts of your foot and could lead to problems like shins splints, achilles tendonopathy, tib post tendonopathy, metatarsal stress fractures, bunions etc.
What To Do
Fortunately, if you don’t have good flexibility in your big toes, it’s really easy to start working on it. I tell my clients to do some simple stretches every day while they brush their teeth. It’s easy to remember and the key to improving flexibility is consistency. Just get in the habit of doing it every day while you brush your teeth.
The stretches are really simple. Simply push your big toe into extension on the floor for about 30 seconds and then into flexion for about 30 seconds. Then do it on the other foot. Keep doing that until you finish brushing your teeth. Easy.