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.

Chinese Bamboo Tree and Coaching

When it comes to coaching, I often talk about building your coaching skills. Many people in our profession today are self proclaimed experts. These gurus are great at marketing, but haven't actually developed their coaching skills in the trenches with real athletes, but they're still happy to tell you how to do it.

This year I will be turning 40 and I am really looking forward to it. With the New Year, it’s been a time of reflection and I’ve been thinking about where am I actually heading, where do I want to go now, and what do I have to do to get there?

True sports performance coaching isn't just about results today, its about developing complete athletes. When it comes to developing speed, whether its young athletes or pros, it takes consistent, quality work, to bring about change.

Some years ago, I heard this story about how Chinese Bamboo Trees grow. I thought it was very insightful and really underlined much of what I believe about developing both coaches and athletes.

“Energy and persistence alter all things.” - Benjamin Franklin

1st Year - You plant a bamboo seedling and give it proper sunlight, water, nourishment and in the first year except for a tiny sprout, there is no growth.

2nd Year - During the second year you care for the bamboo in the same way. You give it constant attention, watering, sunlight and maybe you even throw in some praying, but still the bamboo does not grow. You were told it might take a while to grow, so you keep soldiering on.

3rd year - Another year goes by. You give the bamboo the same love and care. You keep giving it the best fertilizer, sunlight, water, but again much to your amazement, nothing happens. You start asking yourself, why isn’t this thing growing? It’s at this time many people just throw their hands up and give up, but no that’s not you. But how discouraging is it that you’ve waited patiently and cared for this bamboo only to have nothing happen?

4th Year - During the 4th year, you care for it, fertilize it, and give it proper sunlight. You take a look around the garden and realize that all the other plants are blooming and teeming with life and vibrancy. But your poor bamboo seed has nothing to show for. For four whole years, you’ve been patient and truly tried to help this seed grow. Except for a tiny sprout, your bamboo is no bigger than it was during the first year.

5th Year - It is not till sometime in the fifth year the bamboo tree will start to grow. And when it decides to grow, what happens in the next 4-6 weeks is astonishing. The tiny bamboo sprout you cared for will grow as much as 3 feet in a day until it reaches as high as 90 feet. Many people see this success and think its amazing for a tree to grow like this in 4-6 weeks. It didn't, it took 5 years of persistence plus 4-6 weeks.

While in the first through fourth years, the plant was not growing above ground, it was actually growing below ground. It was developing miles of its intricate root system which would eventually help propel its massive upward growth in year five. The bamboos’ intricate root structure takes four years to prepare itself for the growth it will experience in its 5th year.

Becoming a great coach is very much like the growth of the bamboo tree. You can do everything seemingly right, but still not have the recognition of the internet gurus, or the coach from the winning team, or the big pro job you want. Just remember, although you may not be growing above ground, you just might be developing your root system. The system of art and science of being a great coach. Hopefully it will one day ultimately propel your growth. Keep persistent and never give up.

Motor Control Theory

I spoke yesterday at the NSCA Sport Specific Conference on Sprint Technique and its relevance to teamsports. One of the key topics for this which I bought up was motor control theory. It generated the most questions after the session and Dynamic Systems Theory was new to most.

If we step back and look at kinesiology education in the US, motor control is often just a side note or after thought. That which is covered is still generally based on the idea of a general motor program and schema theory. Every coach does need tolern this, but it is not up to date and does not answer many of the complexities we encounter dealing with team sports and human movement.

I was fortunate to have a biomechanics instructor in grad school who introduced me to the other theories. Then another stroke of luck was finding an old book when browsing through one of my favorite sections in the library. The Co-ordination and Regulation of Movements by N.A. Bernstein. This book opened my eyes. It lead me to a much larger view of motor control, and provided an answer tomany of the short comings in GMP theory that just didn't explain what I saw going on in sport training. Progress in Motor Control, Volume One: Bernstein's Traditions in Movement Studies
by Mark Latash from Penn State is another great one to bring it more up to date.


If you are involved in coaching speed and agility to athletes in any way, you need to have a personal understandingofmotor control theory. If you don't, how can you justify what you are doing? While will those drills matter and how will they transfer to performance?

I am going to go more into motor control in comingposts and it will be the topic of a ceu webinar in March. This article on SPORTSCI.ORG is a good starting point to get introduced in the mean time.