Running involves cyclic movement of the legs and includes a period of time when neither foot is in contact with the ground this is called the gait cycle. How the foot moves in this cycle determines a foot type, and as such the construction of the ideal running shoe to best help with shock absorption and prevent injuries.
The Gait Cycle
The gait cycle consists of two movement periods: swing and stance. The swing period is the movement of one leg while its foot is in the air. The stance period is the period of movement of the leg and foot while the foot is in contact with the ground. The stance period may be divided into the following three phases.
This phase is initiated when the foot makes contact with the running surface with forces of two to three times the runner’s body weight impacted on the runner’s body.
For many runners this is a heel strike. For ideal running form it is better to have mid foot strike.
The support phase consists of the foot supporting the body as the foot transitions from heel to toe. This happens mid-stance of the gait cycle.
Controlled elongation of the arch ensures proper support and allows for neutral pronation.
Too much elongation of the arch will tend to result in over-pronation, while limited elongation of the arch will tend to result in supination.
This is the toe off movement phase where forces are distributed across the forefoot and the arch stiffens as the foot prepares to push off the ground.
The foot-strike characterizes the movement of the foot as it goes through the three phases of stance in the gait cycle:
Running can compound forces and motions that lead to injury so ideally for a neutral foot-strike, the foot should contact the ground and roll slightly outward before rolling slightly inward to absorb as much shock as possible.Then before the foot leaves the ground, it should roll slightly outward again to combine these subtle movements allowing the foot to function correctly in absorbing and dissipating ground forces. This is neutral pronation.
However, too much or too little movement usually leads to problems such as severe pronation or supination.
Neutral pronation is the slight inward rolling movement of the foot during its foot-strike.
Neutral pronation is considered to be the ideal motion of the foot during running and walking and greatly reduces the risk for injury.
People with neutral pronation tend to find success in neutral shoes or mild support shoes.
Over-pronation is excessive inward rolling (pronation) of the foot during its foot-strike and often creates alignment problems within the legs. There is a wide range of degrees of over-pronation.
Minimium support shoes, moderate support shoes and maximum support shoes are designed for feet, which need some guidance to steer the foot along a path of neutral pronation.
Moderate motion control shoes and maximum motion control shoes are designed for the most excessive degrees of over-pronation and work to control the motion of the foot.
Supination is the lack of an inward roll or a rolling out of the foot during its foot-strike. This motion inhibits the foot’s ability to absorb ground forces. Can be referred to as under-pronation, a foot that supinates needs a soft ride and quick heel-to-toe transition.
Good flexibility in a shoe is desirable so minimum neutral shoes and moderate neutral shoes work well for supination.
How to determine your foot motion
If you do not know what type of motion your feet have and do not have the opportunity to have your foot motion evaluated by someone else, you can try to estimate your foot motion yourself.
A good indirect measure of foot motion is the wear of the midsole of your current running shoes.
You can look at the creasing in the midsole foam if it has an EVA midsole, however a shoe with a polyurethane midsole will not show creasing. Fortunately, most running shoes are made with EVA foam midsoles.
As a shoe is worn the midsole breaks down and creases will develop. The greater the number of stacked creases or deeper creases the greater wear.
Older shoes will display creases without pressing while shoes with less mileage will need to be compressed with your hands.
- A neutral foot-strike will create creasing in the lateral heel of the midsole and medial forefoot of the midsole.
- Excessive creasing of the midsole in the lateral midfoot suggests that supination is occurring.
- Excessive creasing in any part of the medial side of the midsole from the heel to just before the forefoot suggests that the foot is experiencing over-pronation.
Another indicator of your foot motion is outsole wear of your running shoes.
The pattern of wear on the outsole may represent how forces are distributed along the shoe during stance and can resemble the foot print images above.
A wet footprint test is a simple method for determining foot motion. Get your feet wet and stand on a flat surface that will allow your footprint to be shown. Compare the results with the images above.
However one problem with the wet footprint test is that it is a static measure and feet have dynamic movements during stance while running. To make the wet footprint test better, compare seated footprints with standing footprints. If the standing footprint has a greater surface area than the seated footprint then you probably need some pronation control.
Another problem with the footprint test is that some people have footprints that match the above images but their feet do not move in the indicated way.
Although the relationship is not always the case, there is a tendency for foot motion to be associated with arch height.
As a generalisation, the higher the arch the less the foot will pronate and the lower the arch the more the foot will pronate.
To check your arch, stand on a hard surface and view the medial side of your foot in a mirror or take a picture of your foot and compare it to the images below.
Arch height works best as an indicator of foot motion for people at the extremes – either severe pronation or supination. However, there are people with high arches that over-pronate and people with no arches that will supinate.