What’s so important about heel lifts? (part 1 of 3: biomechanics)

Let’s talk a little bit about lower extremity biomechanics and how a heel lift can alter normal biomechanical properties.

The calf, ankle and foot are a lever.  The primary function of this lever is to enable walking.  To do so, the calf contracts and delivers a force to the ball-of -the-foot.  The action created by that force is to lift the heel just a bit, but more importantly, this force causes us to begin a forward fall.  That forward fall is due to our center of gravitiy being pushed forward.  As we begin this fall, we react by placing our other foot out to stop the fall.  But to continue walking, the second foot will perform the same task; calf contracts, raises the body just a bit and we continue forward in our forward fall.  That’s what we call walking.  Granted, there’s a lot more to the biomechanics, but what’s at the heart of walking is how the leg, ankle and foot act as a lever to lift us and move us forward.

So what’s a lever?  Levers have three parts.  Force is created by what’s called the effort arm.  Force is received by the opposite end of the lever called the resistance arm.  And in the center is a hinge that enable this transfer of force called the fulcrum.  There’s a number of common examples of levers in life that we use every day such as a nut cracker, pry bar or a teeter totter.  The way that the lever works is that force is generated at one end and received at another.  Still hanging with me?

So in the leg, ankle and foot, we have the calf acting as the effort arm, the ankle acting as the fulcrum and the foot acting as the resistance arm.  With each step, force is delivered from the calf to the foot. 

So what does a heel lift have to do with lever function of the leg, ankle and foot?  The humble little heel lift actually performs a big function.  Raising the heel will weaken the calf.  By weakening the calf, there will be a decrease in the amount of force carried down through the lever with each step.  A small heel lift (3/8 to 12″) can have a significant impact on the amount of force delivered through the lever we call the leg, calf and foot.  But more importantly, think of the sum total of force carried through this lever over the course of a day.  If you change each step so that there’s less force, think of the impact of that change at the end of the day….it’s significant.

Interested in more information on this topic?  Visit our pages on the CT band for a more complete summary of lower leg lever function.

Jeffrey A. Oster, DPM
Medical Director
Myfootshop.com