“Ask the Expert” is regular feature of the Natural Running Center. If you have any running-related questions — shoes, diet, gait, injury, transitioning– let us know, and we will do our best to have an expert from our NRC Advisory Board answer them.

Kick-off question: Should heavier runners use thickly cushioned shoes to lessen the impact of repetitive force stress on their joints?

Dr. Casey Kerrigan responds:

The answer is no. Being overweight increases the risk for knee osteoarthritis so most certainly for a heavy runner, consideration of the forces through the knee joint should be given the highest priority. I think a heavier Clydesdale-type runner should stay clear of any cushioned shoe from the start. Because, indeed, although the idea that a traditional running shoe increases forces through the knees is counterintuitive, that is exactly what we found in the gait laboratory.  But the increased forces we found were not at impact. The peak forces that are associated with knee osteoarthritis always occur later in the stance phase when the foot is fully planted – in midstance.

This is the case regardless of running form or whether or not someone is wearing shoes – minimal or otherwise. It is at this point in the gait cycle, when the foot is fully planted, and the foot and the lower leg are absorbing and releasing the body weight in preparation for the next step, that joint torques (which relate to joint forces), and really all stresses and strains related to common injuries, are the highest. This is the point when runners are at risk for osteoarthritis, and virtually ever other major injury, including stress fractures.

A cushioned shoe does not increase joint torques at impact. But what cushioning does do, which is harmful, is make the joints work harder, later, in midstance. Despite all the so-called advances in foam, gel and air filled bladder technologies, the typical midsole compresses and releases out of sync with the rise and fall of the body weight. By working out of sync, a cushioned midsole makes the joints (and all injury prone areas for that matter) have to work harder, which we see by way of the greater joint torques.

My recommendation: the heavy runner should run in a shoe with no cushioning.