Vertical Ground Reaction Forces Produced in Shod Running vs. Barefoot Running

This study turned up in my alerts this morning. It was an undergraduate project from Fort Lewis College in Colorado that has not been ‘published’, but is in poster form and was presented at School of Natural and Behavioral Science Undergraduate Research Symposium on the April 18th. Knowing what my students achieve as part of these sorts of projects, this project is pretty impressive for this level! Here is the abstract:

Vertical Ground Reaction Forces Produced in Shod Running vs. Barefoot Running During a Moderate-Intensity Jog
Fort Lewis College: Exercise Science Department, Exercise Physiology Option
Randee O’Brien and Melissa Knight-Maloney, PhD
The focus of this study was to compare ground reaction forces produced in shod running vs. barefoot running during a moderate-intensity jog. Ground reaction force data was collected indoors on a 16-foot firm, flat surface using a force platform. Prior to data collection, each subject was asked to select a comfortable running pace. The subject-selected running pace was to remain consistent and was used for all trials. Each subject completed five trials barefoot and five trials in their personal running shoes at the subject-selected speed in a random order. No significant difference was found between the vertical ground reaction forces produced by shod (M=321.05, SD=58.11) and barefoot running (M=317.79, SD=57.98), t(df)=15, p=0.21. However, the calculated mean forces produced by shod running were greater than barefoot running. Results indicate that the differing ground reaction forces produced by shod and barefoot running most likely occurred on an individual basis and therefore cannot be generalized to a larger population.

Essentially what this study showed was that there was no statistically significant differences in the vertical ground reaction forces between shod and barefoot running, which is somewhat counter intuitive, especially in the context of all the rhetoric and propaganda that you can reduce impact forces by ‘barefoot’ running.

This was an acute intervention and a within subjects study, so there is no knowing if the lack of differences would remain after a period of habituation.The cynic in me can see the crankosphere blogosphere spinning this in different ways. Those that don’t like the results will spin the lack of habituation issues as a flaw, but will happily accept the results of other studies that did not have a habituation period! (for eg, see: The ‘Running Shoes Causing Knee Osteoarthritis’ Debacle).

Other studies have reported similar as well as dissimilar results, so this just points to more work needed to answer why different studies are getting different results. It does perhaps point to the subject specific responses that we are seeing in other studies to changes in running techniques as being really important (ie see: What is the “best” running form?).

As this study was to do with impacts, its probably timely to re-post what I wrote in another thread on impact forces:

I really struggle to understand why there is so much fuss about reducing impact loads and loading rates. Everywhere you go in the crankosphere blogosphere heel impacts are the cause of all evil and have to be eliminated at all costs. As I always go where the evidence takes me, the evidence to me just does not support the strength of that contention:

  • Nigg (1997) summarized his and other research and reported no differences in injury between those with higher or lower impact peaks and found a correlation between higher impact loads and less injuries; concluding that: “Impact forces have been associated with the development of musculoskeletal injuries. However, results of epidemiologic studies that assess the association between impact loading and the development of acute or chronic injuries do not support this notion“.
  • The systematic review of the literature and meta-analysis by Zadpoor and Nikooyan (2011) on loading rates and stress fractures found that: “The currently available data does not support the hypothesis that there is a significant difference between the ground reaction force of subjects experiencing lower-limb stress fracture and control groups. Instead, the vertical loading rate was found to be significantly different between the two groups.” They reported that impacts were not a factor, but the loading rate was. This was only for tibial stress fractures that make up ~4-5% of all running injuries.
  • In contrast, there was an abstract presented at the ASB meeting in 2010 by Irene Davis in which they reported that impact factors were associated with an increased risk for injury.

So I am unconvinced that impact loads and loading rates are even a problem or as big a problem as all the rhetoric and propaganda make them out to be. The evidence either way is not compelling. They are a problem for tibial stress fractures, that make up a small number of running injuries. It is possible to spin or cherry pick the research to try and make whatever point you are trying to make or story you are trying to tell. I happy to be convinced otherwise, but the evidence is telling me that heel striking and high impacts are not the big evil that they often get painted to be.

I do hope the authors ‘publish’ this study in full as it does contribute to the topic, if only muddying the waters even more!

As always, I go where the evidence takes me until convinced otherwise

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2 Responses to Vertical Ground Reaction Forces Produced in Shod Running vs. Barefoot Running

  1. Brian Hazard April 26, 2013 at 2:17 pm #

    If they had put a handful of sharp pebbles on the track, we’d have seen a bigger difference! 😉

  2. Kevin A. Kirby, DPM April 28, 2013 at 1:13 am #

    Another study that highlights how insignificant the “heel impact peak” of the ground reaction force vs time might be in injury production during running was done by Shorten and Mientjes in 2001 (Shorten M, Mientjes MIV: The ‘heel impact’ force peak during running is neither ‘heel’ nor ‘impact’ and does not quantify shoe cushioning effects. Footwear Science, 3 (1):41-58, 2011). In their study, they tried to isolate out whether it was just the heel striking the ground that produced the “heel impact peak” or whether the forefoot also contributed to the “heel impact peak”.

    What these researchers found was that the heel impact force peak is composed of both a high frequency heel impact transient and lower frequency heel and forefoot loading peaks. Therefore, these authors concluded that the initial force peak in rearfoot strikers “is neither uniquely defined by heel impact, nor a reliable indicator of impact magnitude”.

    This means that all the researchers that are measuring vertical loading rate and magnitude of the heel impact peak are not only measuring the ground reaction force from the heel striking the ground but also the ground reaction force of the forefoot striking the ground also. This seems to make it even less likely that the heel impact transient seen on the ground reaction force vs time curve is of any significance in injury production in rearfoot strikers.

    As Benno Nigg says: ““Currently, there is no conclusive evidence that impact forces during heel-toe running are responsible for development of running-related injuries.”
    (Nigg BM: Biomechanics of Sports Shoes. University of Calgary, Calgary, 2010. p. 32.)

    Kevin A. Kirby, DPM
    Adjunct Associate Professor
    Department of Applied Biomechanics
    California School of Podiatric Medicine

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