When most of us run, we usually don’t think about the actions our feet go through during a complete cycle from the time when one foot hits the ground until it hits the ground again. This cycle is officially known as a biomechanical process, but to us runners, we know it as our running gait. It can be broken down into two phases: stance and swing.
This phase starts when your foot first contacts the ground and consists of three components:
Heel strike: When your foot comes down, your heel should strike the ground toward the outside edge and back of the heel. You can verify your heel strike by looking at the heel of your running shoes. The outside back edge should show more wear than the rest of the sole. When your heel strikes the ground, the arch of your foot is in its highest position with your body weight centered over your ankle; this is called neutral pronation.
Mid-stance: Once your heel is in contact with the ground, the impact starts to move forward toward the arch of your foot. When the impact, estimated to be three times your weight, reaches the middle part of your foot, your arch begins to flatten out, or pronate, thus creating a cushioning effect that reduces the jarring of the impact and keeps your weight centered over your foot.
Toe-off: As the impact progresses forward along your foot, your arch begins to rise again and the ball of your foot now provides a stable base which allows your toes to push off and propel you forward. While all your toes assist in this effort, your big toe does most of the work.
Your foot is now off the ground and moves into the swing phase.
The swing phase is from the time your foot raises up off the ground until it hits the ground again and it has two components – internal and external rotations.
If you had the proper toe-off, your toes should be pointing toward the center line of your body. At the point where that foot crosses the plane of your other leg, you move into the external phase.
Once your foot that is off the ground crosses the plane of the leg on the ground, it begins to rotate outward. This rotation is necessary so your heel will be in the correct position to hit the ground – on the back outside portion of the heel – the next time it comes down. Now the biomechanical process for one foot is complete.
And this process happens over and over, again and again during the course of a run without us ever thinking about it. Consequently, it is easy to see why running shoes matched to your feet are so important, if you are to get the proper foot support they need to go through all of these actions.
However, the effect is slightly different for some people that have flat arches and are prone to over-pronation. With a flat arch, their foot doesn’t experience the cushioning effect. When their foot comes down, it strikes hard and the impact tends to shift too much of the impact toward inside edge of the foot – called over-pronation; this can cause foot pain. Fortunately, a custom pair of orthotics prescribed by a podiatrist can help support the arch and alleviate this condition.