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photo credit | @yungfeug
by Emmi Aguillard, PT, DPT, FAFS

Posted in Blog.

February 26th, 2020

Get Off The Concrete!

As runners of NYC, we are training in a concrete jungle. Urban running is truly exhilarating – there is nothing that can compare to running through the streets of Manhattan, having the city to yourself and watching it come to life in the early morning, enjoying the sunrise over the Williamsburg bridge or watching the sunset as you run along the west side highway. Don’t even get me started on racing through the streets in the middle of the night. But – it’s important to understand the load and impact that urban running has on our joints and body.


Let’s break it down: some of you might remember the concept of Ground Reaction Force (GFR) from high school physics. This is the force exerted by the ground on the body in contact with it. Even when we are just standing still, the ground is exerting an equal and opposite force on us. When we are walking and our foot hits the ground, the GFR is around 1-1.5x our body weight.  With running, that force jumps up to 2-4x our body weight.

ground force reaction (GFR) = the force exerted by the ground on the body in contact with it


It takes TIME – years, in fact, for our bones, tendons, and ligaments to adapt and respond to the repetitive stress of running. It’s critical to refrain from comparing yourself to others who may be following a high-mileage training plan – the number of years a runner has under their belt is incredibly relevant. If you are newer to running, it’s important to incorporate soft surface runs to help stay healthy and injury-free.


Our body responds to different terrain by adapting it’s loading mechanics – the way in which our foot strikes the ground – in order to help to lessen the GFR on our body. Studies show measurable differences in how our foot strikes the ground, the angle of our knee joint, and our stride in order to adapt to the difference in energy return on these surfaces. Most research comparing runners on asphalt, concrete, and track to have similar loading forces, but different form adjustments in order to reduce impact on these harder surfaces. Peak pressure on the body was reduced by up to 16%, however, by runners on grass Research suggests that when we run on concrete in comparison to a soft surface like grass, we are increasing the peak pressure on the body by up to 16%*.


This is not consistent across the board, however – some people demonstrate a greater ability to adapt to different surfaces, while others show increased loading forces in the joints when running on harder surfaces. With a sport as repetitive as running, these slight adaptations are incredibly important for resiliency! While surface is important to keep in mind, this also highlights the importance of proper running economy – working on form, turnover, and strength in order to improve running mechanics.


Who can benefit most from varying the surface that they run or train on? Anyone with a history of bony injury, knee pain, someone newer to running who is hoping to safely increase mileage, or a high-mileage runner hoping to stay injury-free!


Tips for finding soft surface in NYC:

  • Bridal Path: most people know of the dirt loop around the reservoir in Central Park – did you know that loop actually extends up to the 102nd street transverse and down to Columbus Circle, for almost 6 full miles of soft surface in the heart of Manhattan? 


  • The above graphic is how I rank surfaces as far as how forgiving they are. Research reports varying degrees of difference between these surfaces, the biggest correlation shows significantly reduced ground reaction force of grass compared to concrete. Grab some of your running buddies and plan to meet at a rather boring location – I’ve used the baseball field on the East River in the past! Good conversation will help to make up for the lack of scenery changes, and your joints will thank you!


  • Anti-Gravity Treadmill: We have two at Finish Line PT. This is THE gold standard for reducing load on the body while maintaining mileage. While the amount of decreased force is fairly minimal from surface to surface outside, reducing your body weight by 10-15% and going for a run is THE BEST form of cross-training or recovery run. This is a great option if you want to safely up your mileage, are returning from an injury, or want to incorporate a double. 


  • A brief note about minimalist shoes or barefoot running: a 20 min run in the sand or on a soft, grassy, (sticker-free) surface can be amazing for working the intrinsic muscles of the foot and loosening up a stiff plantar fascia. But – the reality of NYC is that we are POUNDING through our bodies, and having a shoe with cushion that can help to absorb the shock and load that is going into it is important! For a more minimalist style – don’t ditch the cushion, instead, I’d encourage you to try some of the minimal drop shoes. I’m a big fan of the Saucony Kinvara, Hokas, or the Altra brand!


Finally, there are times when the body actually responds better to harder surfaces than a soft surface. If you are coming back from an ankle injury like Achilles, peroneal, posterior tibial tendinitis, or an ankle sprain – the soft surface actually increases the work of foot, with less energy return for each step, requiring more work of these lower extremity muscles. Not sure where you fall in the spectrum? Have a conversation with your physical therapist!


photo credit | @yungfeug


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