Ground Reaction Forces

Ground Reaction Forces are a key component to consider in improving an athletes speed. Today in the track world there are some big arguements in this realm. They can become oversimplified and end as technique training vs. force training. Using the Woodway FORCE treadmill, we actually get to see whats happening in terms of ground reaction forces.

One of the things that surprised me as we started research with this several years ago, was that the horizontal forces are more sensitive to differences than the verical. Coming from the strength side of coaching and having been a weightlifting coach, I had an early bias (and still do at times) towards the "force" side of things. "Build more of the right strength qualitites to improve impulse and they will run faster" My thinking and understanding have evolved dramatically over the last 16 years, but there is still a lot of truth in this.

This ia typical horizontal GRF graph during an unloaded sprint on the FORCE treadmill. It Shows some variability as expected from prior reserach, but no consistent pattern. The athlete is not displaying a significant difference between the left and right legs.
An interesting note is that this athlete had an injury to the knee about a year ago. They rehabbed and played the season. On intake, they reported no pain or problems in this knee. As they were doing the test. this one was bad enough that we could here it before we could see it. However we find this differences even when they are visible or audible.

However, what we often see is below. It doesn't take a Master's degree in biomechanics or motor control to understand there is a problem here. We have an athlete that is generating a fraction of the force on one leg versus the other. This athlete was getting ready for the NFL COmbine where 40yd dash is critical to his draft position and making money. Obviously this can't be optimal. This also has to lead to some seriously unbalanced force through the kinetic chain and may lead to problems in the hips or lumbar spine.



The real key step to any assessment however is how do you use the information to help the athlete. Research is great to help us learn and grow, but for each athlete the questions is "What Now?"

Some we do a number of things. First we will use this data with data from functional movement assessments, joint rom and testing, other performance tests. Then we address the specific strength, stability and range of motion issues on this leg. We will also probably do some additional work on this leg with drills like fast leg, gallops and bounds when appropriate.