Reduction in Ground Reaction Forces with Barefoot Running

One of the more common arguments for barefoot running (or at least transitioning to minimalist shoes or just a forefoot/midfoot strike) is that it is easier to more lightly contact the ground and eliminate the magnitude of impacts associated with a heel strike. Now we have this study that looked at the magnitude of reduction in the ground reaction forces following a transition to barefoot running:

Reduction in ground reaction force variables with instructed barefoot running
Cynthia D. Samaan, Michael J. Rainbow, Irene S. Davis
Journal of Sport and Health Science; in press
Background
Barefoot (BF) running has recently increased in popularity with claims that it is more natural and may result in fewer injuries due to a reduction in impact loading. However, novice BF runners do not necessarily immediately switch to a forefoot strike pattern. This may increase mechanical parameters such as loading rate, which has been associated with certain running-related injuries, specifically, tibial stress fractures, patellofemoral pain, and plantar fasciitis. The purpose of this study was to examine changes in loading parameters between typical shod running and instructed BF running with real-time force feedback.
Methods
Forty-nine patients seeking treatment for a lower extremity injury ran on a force-sensing treadmill in their typical shod condition and then BF at the same speed. While BF they received verbal instruction and real-time feedback of vertical ground reaction forces.
Results
While 92% of subjects (n = 45) demonstrated a rearfoot strike pattern when shod, only 2% (n = 1) did during the instructed BF run. Additionally, while BF 47% (n = 23) eliminated the vertical impact transient in all eight steps analyzed. All loading variables of interest were significantly reduced from the shod to instructed BF condition. These included maximum instantaneous and average vertical loading rates of the ground reaction force (p < 0.0001), stiffness during initial loading (p < 0.0001), and peak medial (p = 0.001) and lateral ground reaction forces (p < 0.0001) and impulses in the vertical (p < 0.0001), medial (p = 0.047), and lateral (p < 0.0001) directions.
Conclusion
As impact loading has been asociated with certain running-related injuries, instruction and feedback on the proper forefoot strike pattern may help reduce the injury risk associated with transitioning to BF running.

I have only two things to say about the implications of study¹:
1. It based on the assumption that reducing the ground reaction forces is a good thing and a desirable goal. As we know, the evidence supporting that is far from compelling (see: Just How Significant are Heel Impacts at Causing Injury When Running?).
2. To achieve that reduction in impact forces, you have to increase the load in some other tissue(s) and that carries an injury risk with it. The authors did not look at this, so did not report it (see: Its six of one and half a dozen of the other: Rearfoot vs Forefoot striking when running).

As always, I go where the evidence takes me until convinced otherwise and this study shows that instruction in the barefoot running technique can be used to reduce the impact forces associated with running …. if that is what you want to do.

1. I have no comments on the methodology and analysis of the results as they all appear fine to me and I can see no issues.

Samaan, C., Rainbow, M., & Davis, I. (2014). Reduction in ground reaction force variables with instructed barefoot running Journal of Sport and Health Science DOI: 10.1016/j.jshs.2014.03.006

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8 Responses to Reduction in Ground Reaction Forces with Barefoot Running

  1. Robert April 29, 2014 at 3:11 pm #

    Hi Craig,

    One parameter that I have yet to see included in the (very few) studies that I have read is a treatment of the strain rate sensitivity of the tissue and bone involved in the impact event. Soft bio-tissue and bone both exhibit high strain rate sensitivity. What this means is that the rate at which the material is loaded plays a large role in the mechanical response of the material. Typically at high strain rates (such as is seen in the transient loading during running) soft (e.g. some viscoelastic) materials respond as if they are much stiffer (higher modulus) and stiff materials (such as bone) exhibit a higher degree of brittleness (i.e. a lower strain to fracture).

    A simple thought process would conclude that the tissues and bones involved in the initial impulse force will exhibit a greater net stiffness and therefore efficiently transmit the impulse (shock wave) up the leg and to the knee, etc.- a least this was what was explained to me when I visited the biomechanics lab at Harvard. In addition, the bone would be more susceptible to fractures of all sizes due to the increased brittleness at high strain rate. It makes sense to me but I have yet to see a full treatment that includes these loading-rate-dependent properties in any calculation or model of the impulse forces during running as a function of foot-strike. Perhaps there is work out there.

    To your point 1 above: it is possible that reduction of ground reaction forces is not the issue- it is reduction in reaction force rate (i.e. strain rate) that controls?

    To your point 2 above: if the foot-strike type (forefoot, rearfoot, etc.) at impact sufficiently controls the regime of strain rate (this is a big question), then there could be situations (say, forefoot stike) where the bio-materials involved in the impact exhibit a higher degree of viscoelastic behaviour where the “materials system” will have a higher capacity to absorb the energy of impact by viscoelsatic deformation of the tissues and therefore reduce the magnitude of the shock wave?

    Just some thoughts. Thanks for your continued critical reviews, I enjoy reading your analyses.

  2. Elayna May 2, 2014 at 4:24 pm #

    It is not as technical as all you medical people make it. Man was born barefoot and went barefoot without injury for many years until NIKE, (the inventor of the “sneak”er), compromised the natural bio-mechanics of walking and running. Confining the foot inside a shoe whereby the toe box restricts the natural desire of the foot to splay results in an inability for the foot to properly disperse shock up the leg. This confinement actually causes the foot to strike harder searching for stability. This is where sneaker=injury. Improper dissipation of shock up and out of the leg almost always results in injury at a joint – typically knee then hip. Back to basics. Barefoot. All this analyzing and researching is just to keep you PT and other medical people busy justifying those expensive degrees you are still paying for.Ridiculous to even hear a proposal about how to gradually assist someone in transitioning to BF running. Absurd! Just Do It!

    • Craig Payne May 2, 2014 at 5:26 pm #

      How do you explain all the evidence that shows that impacts are not related to injury? None of what you say is supported by the evidence ; what you are claiming is contradicted by the above study – so why do you choose to use an argument against researchers rather than stick to the topic; typical and absurd.

      How do you explain all the research that shows the injury rates between barefoot/minimalist is the same as traditional shod?

      • Conrad June 4, 2014 at 7:01 am #

        Hi Craig,

        I’m not disagreeing with you, but your statement that injury rates between barefoot/minimalist is the same as traditional shod, is just as absurd without the data to prove or substantiate such a statement. Could you provide the data comparison over a 20 year period? A comparison between the injury rates between people who have run in traditional shoes vs those who have run barefoot their whole lives would also be relevant?

        My burning questions are how do we have years of running and technology advancement but still see so many injuries? Secondly if somebody was about to start running or was a teenager moving into longer distance running who only wears racing flats currently – what would be your advice?

        • Craig Payne June 4, 2014 at 7:37 am #

          Why is it absurd? Have you even read the studies? The preponderance of evidence is clearly showing that the injury rates between barefoot/minimalist runners is the same as those who wear traditional running footwear. There is plenty of data to back that up. Where are you getting your information that there is no data?

          I have no idea re years of running and technology and injuries. I have been asking that question since the 1980’s. What is now clear is going minimalist/barefoot is not the answer either. That is what the data is showing.

          As for what advice to give you… why would you want any advice? If it ain’t broke, don;t fix it. Keep doing what you are doing if you are having no problems.

          • Conrad June 4, 2014 at 7:26 pm #

            I have not seen all the research that makes this inference and you have not listed any – I’m not saying there isn’t. Have you read Tread lightly by Peter Larson?

            As for the keep doing what you’re doing, I’m wondering what your position is for somebody who doesn’t know as he is a newbie – no previous running experience? which approach would be the most reasonable? since both are equally bad or equally good, how do you decide? Try minimalist or traditional shoes?

            I know its not a perfect science, I’m just wondering if its true (scientifically proven) that the injury rates are equivalent, it just doesn’t seem reasonable that both approaches would produce such similar results – when the styles are so varied.

  3. Ian Griffiths May 8, 2014 at 8:04 am #

    Looks like someone has read Born to Run…

    • Craig Payne June 5, 2014 at 2:26 am #

      Conrad – something wrong and there s not a ‘reply’ button to your post!

      “I have not seen all the research that makes this inference and you have not listed any – I’m not saying there isn’t. Have you read Tread lightly by Peter Larson?”

      I have blogged extensively about the research and so has Peter Larson on his blog! – he makes the same comments that I do. Yes, I have read Tread Lightly.

      “I’m wondering what your position is for somebody who doesn’t know as he is a newbie – no previous running experience? which approach would be the most reasonable? since both are equally bad or equally good, how do you decide? Try minimalist or traditional shoes?”

      I am not blinded by any agenda when it comes to a newbie. It will come down to what they are comfortable with; what they want to do; what tissues are likely to be loaded more if they run a certain way and if that is going to be a problem – joint axes positional variations play a big role here. If they overstride and have history of tib ant pain –> minimalist or encourage forefoot striking; eg 2: if the have medial STJ axis and high supination resistance –> probably going to need >12mm drop and have no choice but to heel strike.

      “I know its not a perfect science, I’m just wondering if its true (scientifically proven) that the injury rates are equivalent, it just doesn’t seem reasonable that both approaches would produce such similar results – when the styles are so varied.”

      As I keep saying, different running techniques load different tissues differently – all the biomechanical studies are showing that. You can’t reduce the load in one tissue without increasing it in another. Its never about one being better than another. ,…. it just the injury risk profile is different with different ways of running….what suits one will not suit another. Loads in tissues are influenced by volume of activity and variations in lever arms that tendons have to joints –> these vary massively from person to person –> affects loads in tissues and running economy –> no one blanket recommendation.

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