Having flat feet, or what is more accurately described as 'over-pronated feet', causes a person to use more energy in walking. Over-pronation is a more accurate term because even those with arches that appear high can have the same clinical picture as those with overt flat feet.
During gait the foot goes through several subtle movement changes. Pronation is one of these movements. Pronation occurs when your lower leg rotates inwards from the knee down. In this position, your foot is wider and longer. The pronated foot is flexible and it happens just after your heel strikes the ground. Pronating at this time makes your foot flexible thereby allowing it to adapt to the ground you've just stepped on.
The term 'over-pronation' means that the foot is in a flexible position all the time and this isn't good. There are times in the cycle of walking and running that the foot must be rigid to form a firm lever for the leg muscles to pull against. Rigidity in the foot should occur as the foot is propelled forward towards the next step. The motion that makes the foot rigid is the opposite of pronation called supination.
If the foot is pronated or flexible at the point of propulsion instead of rigid or supinated, much of the explosive muscle power required from the legs is lost to the loose joints of the foot. So people with flat or over-pronated feet have to use a lot more energy than those with normal feet to walk or run. This extra energy really adds up during the course of a day and the overall net result is fatigue and tired and aching feet.
For many years, health practitioners have reasoned that this should be the case with people with flat feet who complained of fatigue or aching legs and feet. Now thanks to a recent study, the common theory seems to be proven.
This theory was proven by a research project reported in the Journal of the American Podiatric Medical Association (2000;90:30-34). Two groups of women were used in the study. One group was made up of 20 women who had normal feet while the other group of 20 had over-pronated feet confirmed by weight-bearing analysis and x-ray studies. The study consisted of both groups walking on a treadmill at 3 different speeds and inclines. Multiple measurements were taken during this period of exercise: ECG, blood pressure, pulse rate and oxygen consumption; both before, during and after the exercise.
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