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.

NFL Draft Speed Testing

As we are in the midst of NFL Combine Prep, we are doing a lot of assessments. One of the elements of our assessment process, is using the Woodway FORCE treadmill from Woodway.

One of the unique things we get from this is the actual measurement of Ground Reaction Forces. It's self propelled and the athletes have to do the work. Over the last several years, one of the things we have learned with research is that many old injuries show up in un-even force production. We regulary see athletes that are sufferring no symptoms, but end up putting very un-even force into the ground.

This has several implications from un-tapped performance potential, to unbalanced stresses that may increase injry risk and overuse.

Mark Sanchez is pictured here during testing and he had great results, but thats not what we see from everyone.


We have tested 100's of athletes over the years, and while some we can pick up with our eyes and ears, those great tools don't tell us everything. It is amazing what we find, and even greater when we can do something about it. Finding an athlete has a significant difference, lets us target their specific needs and make a difference.