Last Friday I traveled down to Boston to give a research presentation at the Spaulding National Running Center. I was invited by Dr. Irene Davis, one of the world’s leading experts on running gait and injuries, and it was awesome to be able to spend an afternoon at a top notch gait lab. I got to chat with Irene for a bit about her clinic’s approach to treating running injuries (gait retraining is emphasized), met with her clinic/lab group, and gave a talk on my running foot strike research (with a surprise attendee – Harvard’s Dr. Daniel Lieberman).
As part of the visit, I was able to run on the force treadmill that is a centerpiece of the clinic (they also have a long runway with embedded force plates). I’ve run on force treadmills a few times before, but the nice thing about the Spaulding lab is that it’s set up to provide a simple report for patients that come to the clinic. I thought I’d share my results here.
Just to give a quick overview of what was done, I ran at a relatively easy pace (>10:00/mile) in both shoes (New Balance 1400 v2) and barefoot. While I ran I was able to see my vertical ground reaction force profile on the screen in front of me, which was very cool. It was fun to make the impact peak appear and disappear by forcing a pronounced heel strike. I tried my best to run with my natural gait, which tends to hover around a midfoot strike, though may move backward or forward depending on the shoes on my feet.
Here are the videos and results:
Video – New Balance 1400 v2 Side View
Video – New Balance 1400 v2 Posterior View
Right Foot Results – New Balance 1400 v2
Left Foot Results – New Balance 1400 v2
Video – Barefoot Side View
Video – Barefoot Posterior View
Right Foot Results – Barefoot
Left Foot Results – Barefoot
One of the big debates in the running form world lately is whether or not impact peaks or loading rates are a major cause of running injury. The impact peak (see image below) is a rapid initial spike in the vertical ground reaction force (Fz) plot that occurs when the foot initially touches down. It is largely a function of the foot and lower leg making contact and does not reflect the weight of the entire body bearing down yet.
What you’ll notice in my plots (left box in each image) is that the impact peak is small to non-existent in most of them, especially in my left foot barefoot plot. The other three plots typically show a small impact bump. This is typical for a non-heel striking, non-overstriding gait. In the videos you can see that my shin is roughly vertical at contact, and I tend to land midfoot or forefoot most of the time (based on my wear patterns, I’m pretty sure I do heel strike a bit when I run, but not in these videos). In addition to the lack of an impact peak, my vertical loading rates are lower than average. Vertical load rate is essentially the speed at which force is applied to the body at contact. My values range from 38-48 Bw/sec, with the lab average being 75 Bw/sec. Interestingly, the vertical loading rate on my left leg dropped about 8 Bw/s when I took off my shoes, right leg stayed pretty much the same. Not sure why there was a difference.
A couple of other things to note:
1. My cadence computed from my stance and swing times comes out to around 165-170 steps/min. My normal running cadence at a comfortable pace outdoors is around 182-185 steps/min, and since I was running on the treadmill at >10:00/mile pace this seems about right for a pace about 2:00/mile slower than what I typically run (cadence changes with speed).
2. My swing time on the right was consistently shorter than the left, again not sure why or if it matters.
3. My leg stiffness was pretty consistent across the board at 16-17 kN/m, and this is higher than average. Leg stiffness is the ratio of the maximal vertical force to maximal leg compression during stance. So, either my max vertical force is higher than average, or my leg doesn’t compress as much as for other people (I guess I’m not springy). I tend to have a fairly flexed knee at contact, and my guess is that I tend to bend it a bit less after initial contact than average. I’m wondering if my tendency toward higher leg stiffness might explain why I tend to prefer softer shoes?
4. I really have no idea how to interpret medio-lateral or antero-posterior force plots, so if you do I’m happy to hear your thoughts!
So there you have it. I wish the videos captured my waist and trunk movement as I see a lot of people with hip drop issues, and Irene indicated that excessive thigh adduction/hip adduction is one of the biggest risk factors for injury that they deal with and is one of their main targets for gait retraining (along with reducing loading rates). Excessive thigh adduction is typically manifested by the thigh angling inward to a greater degree during stance and minimal space between the knees during swing through.
I’ll end with a brief plug for the Spaulding National Running Center – they are looking for barefoot and minimalist runners (with minimalist meaning most miles in shoes with zero to minimal cushion) to analyze in the lab. If you are in the Boston area and meet these criteria, you might qualify for a run on the force treadmill. They also treat running injuries, so contact them if you are in need!