Effect of Barefoot Running on Strength, Balance and Proprioception

A lot of claims get made for the effect that barefoot or minimalist running has on muscle strength, but there is a lack of good data backing up the volume of the rhetoric and propaganda you keep reading on this. Given the volume and strength of the claims you would have thought that there would be some. I commented on a couple of small weak studies here that showed that its not the case and another study with a faulty analysis that claimed there was, so the evidence is far from compelling if that is the case or not. Now we have this new study:

Barefoot Running; The Effects of an 8-Week Barefoot Training Program
Scott Mullen, Jon Cotton, Megan Bechtold, E. Bruce Toby
Orthopaedic Journal of Sports Medicine March 2014 vol. 2 no. 3 2325967114525582
Background: It has been proposed that running barefoot can lead to improved strength and proprioception. However, the duration that a runner must train barefoot to observe these changes is unknown.
Hypothesis: Runners participating in a barefoot running program will have improved proprioception, increased lower extremity strength, and an increase in the volume or size of the intrinsic musculature of the feet.
Study Design: Randomized controlled trial;
Level of evidence, 2.
Methods: In this 8-week study, 29 runners with a mean age of 36.34 years were randomized into either a control group (n = 10) who completed training in their regular running shoes or to an experimental barefoot group (n = 14). Pretraining tests consisted of a volumetric measurement of the foot followed by a strength and dynamic balance assessment. Five subjects completed the pretests but did not complete the study for reasons not related to study outcomes. Participants then completed 8 weeks of training runs. They repeated the strength and dynamic balance assessment after 8 weeks.
Results: Significant changes from baseline to 8 weeks were observed within the barefoot group for single-leg hop (right, P = .0121; left, P = .0430) and reach and balance (right, P = .0029) and within the control group for single–left leg hop (P = .0286) and reach and balance (right, P = .0096; left, P = .0014). However, when comparing the differences in changes from baseline to 8 weeks between the barefoot and control groups, the improvements were not significant at the .05 level for all measures.
Conclusion: Although statistically significant changes were not observed between the pre- and posttest evaluations in strength and proprioception with the 8-week low-intensity barefoot running regimen, this does not necessarily mean that these changes do not occur. It is possible that it may take months or years to observe these changes, and a short course such as this trial is insufficient.

This study recruited a group of runners who were then randomized into a keep what you doing group and an intervention group that undertook what is probably a low intensity barefoot running program for 8 weeks. A number of strength and balance measurements at baseline and follow up were done. They generally reported within group statistically significant improvements in both groups, but no difference between the groups; ie barefoot running did not improve the strength and balance parameters.

However, the reporting of this study falls very short of providing the information that is needed to properly appraise it. It certainly does not comply with the CONSORT statement on the analysis and reporting of randomized controlled trials. Here is a partial list of the issues (its only partial as I don’t want to bore readers!):

  • there were differences in the baseline age and weekly distances run between the two groups; no statistical test is reported as to if they were statistically significant; though they did claim they were similar. The mean age of the control group was 39.7 and for the barefoot group it was 35.5 – that does not look similar to me and given they did not report the standard deviations or do a statistical test we have no way of knowing.
  • no reliability or repeatability data was provided on any of the baseline and follow up tests that they did.
  • in the methods section they claimed an intention to treat analysis (which is what you should do to deal with drop outs according to the CONSORT statement), but then in the results it appears as though they did not do it!
  • in the results section, they put substantial emphasis on the within groups analysis which is not how you analyse a randomized controlled trial (as per the CONSORT statement), but they did also report the between groups analysis which is the key outcome statistic of  randomized controlled trial.
  • absolutely no data is presented (preferably in table form) of the actual results. We do not know what the mean and standard deviations are for each of the baseline and follow up tests. They just mention the percent changes in the variables and the p value. That is not close to enough data for transparency.

All of these issues should have been addressed in the pre-publication editorial and peer review process.

What then do we do with the study?

  • on one hand it should probably be ignored due to the above shortcomings in the reporting which is disappointing as that the point of editorial and peer review is to make sure publications meet the appropriate standard. Something went wrong with this process this time.
  • on the other hand, the study did show that the barefoot running group did not get an increase in strength (which is something the fan boys make a lot of noise about) and the control group did not show any weakness from wearing running shoes (which is something the fan boys make a lot of noise about).

Its a difficult call to know which way to go with this. Those who do not like the results could say the sample size is too small (but then happily accept smaller sample sizes of other studies they like the results of). I do not reflexly have a problem with smaller sample sizes and prefer to look at things like effect sizes and probability of statistical error, as well as trends. We can’t see if there is a trend in this study or not to know if a larger sample size could have the potential to pick up differences, as they did not provide enough data to make that judgement.

Another issue that some might have is the intensity that the barefoot group went through with only two barefoot sessions per week (an interval session and a longer run). By week 8, they had built up to:

Run 1: 4-minute run, 3-minute walk, 2-minute
run, 30-second walk, 1-minute run, 3-minute walk,
2-minute run, 30-second walk, 4-minute run.
Run 2: 4.8-km run.

Given that there was only one injury in the whole study (a post tib problem in one participant in the barefoot group) and what we know about the higher incidence of injury during the transition to barefoot it is hard to believe that the barefoot program was of much intensity. This is even the more surprising given that both groups showed a within groups improvements in many of the parameters measured.

As always, I go where the evidence takes me until convinced otherwise, and this study (like several others I have recently reviewed) points to a failure of the peer review process being way too common.

Mullen, S., Cotton, J., Bechtold, M., & Toby, E. (2014). Barefoot Running: The Effects of an 8-Week Barefoot Training Program Orthopaedic Journal of Sports Medicine, 2 (3) DOI: 10.1177/2325967114525582

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4 Responses to Effect of Barefoot Running on Strength, Balance and Proprioception

  1. Kevin A. Kirby, DPM March 17, 2014 at 2:51 am #

    Craig:

    One factor worth considering is that as soon as people know that they are starting to be studied in a research project, they may start doing things differently….even in the “control group” which could explain the improvement in strength in both groups. In addition, improvement in motor tasks such as a single-leg hop and “reach and balance” may occur for the simple fact that in a study where the activity is first done at the beginning of the study and then done at the end of the sutdy again, there may be improvements in neuromuscular coordination due to repetition of motor tasks. I don’t know if the authors considered either factor.

    One final note, why do the authors include this conclusion in their abstract?

    “Although statistically significant changes were not observed between the pre- and posttest evaluations in strength and proprioception with the 8-week low-intensity barefoot running regimen, this does not necessarily mean that these changes do not occur. It is possible that it may take months or years to observe these changes, and a short course such as this trial is insufficient.”

    If the study did not show statistically significant changes, then it could also mean that the changes may never occur, no matter how long the study. It is also possible if the study went longer, even more injuries could have occurred in the barefoot runners which would have definitely decreased the strength of their feet due to non-activity. We really don’t know what would happen, do we…… researchers! In other words, don’t speculate one way or another….otherwise you look quite biased and not objective!

  2. Rodger Kram March 18, 2014 at 8:53 pm #

    they hypothesized improved proprioception.
    Proprioception = ability to sense joint position.
    I don’t see that they actually measured that.
    usually it is a good idea to measure the variable about which one has hypothesized.

    • Craig Payne March 18, 2014 at 8:55 pm #

      Roger – they mentioned proprioception many times, yet did not measure it; my best guess is that they were wrongly equating the “balance” measure with “proprioception”

  3. Brian Daly March 1, 2016 at 12:17 pm #

    Hi Craig you mentioned this is only a partial list of issues you had with the paper. Don’t worry I won’t be bored but could you elaborate please I would like to get your insight?

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