Born to Run? Exploring Dr. Irene Davis’s work on gait and running

During 2013-2015 I had the good fortune of volunteering at the Biomedical Imaging Lab at UCSF. The post doc researchers there were working on several cool movement science projects. The project that I was able to volunteer on was a longitudinal study that looked at cartilage volumes within the knees of folks who had been diagnosed with osteoarthritis. People living with knee osteoarthritis often assume a toe out gait. Because how we move changes forces at the joints, the theory was that as we taught the subjects to walk with a more mechanically sound posture (in our instance, with their toes forward).

Walking with our toes forward is a crucial aspect of healthy gait, as it allows for the extension at the big toe, the activation of our windlass mechanism within our plantar fascia and maximal efficiency at the calf.

It also protects our knee joints and hip joints from excessive motion in the transverse (rotational) planes. Recall that the knee is meant to function truly as a hinge joint.

Dr. Perry was a foundational pillar for how we understand the biomechanics of walking, and the incredible biomechanist Irene Davis PhD, PT helped us move beyond walking to understand the forces that we expose our bodies to as we run.

Unlike walking, which is a series of double leg stance and single leg stance, running requires alternating periods of flight and single leg stance.

When we add the element of flight, we greatly increase the forces that the body is subjected to. This is largely because of Newton’s law- Force= mass x acceleration. When we run, we greatly increase our acceleration, thereby greatly increasing the forces we must effectively control.

The force we want to specifically explore, is the ground reaction forces. Ground reaction forces (or GRF in movement nerd speak) occur whenever we move over a surface. We push down onto that surface (the earth, a force plate, a diving board) and that surface creates a force back up through our bodies. The GRF increases greatly when we increase either our mass or our acceleration.

Through her years of research into running mechanics, Dr. Davis found that that predisposition for injury is not so much about whether or not we run (or how much) but truly how we ru