Response to the Letter to the Editor for article: The Effects of a Transition to Minimalist Shoe Running on Intrinsic Foot Muscle Size

The Effects of a Transition to Minimalist Shoe Running on Intrinsic Foot Muscle Size. A. W. Johnson, J. W. Myrer, U. H. Mitchell, I. Hunter, S. T. Ridge Int J Sports Med 2016 ; 37 : 154–158

We appreciate the interest in our article, but we have to point out several errors in Mr. Robbins’ assumptions and conclusions, which render many of his comments groundless. Mr. Robbins mistakenly stated that Johnson et al. [2] “tested FiveFingers™ shoes during a period of deceptive advertisement and following initiation of the class action suit.” Our data collection was completed in 2011, prior to the class action suit filed in 2012. Our data collection was part of a larger data collection, a portion of which was previously published in the article by Ridge et al. [4] We stated this fact several times in the article. For example, in the methods section of the paper, we state “determination of BME in both TRS and VFF groups … were previously reported (reference provided)” and in the results section we state, “the TRS group had no significant increase in BME. These data are reported previously (reference provided).”

Mr. Robbins draws false assumptions about differences between the studies which apparently lead him to conclude that we deliberately deceived the study participants and the university’s Institutional Review Board for Human Subjects. He does this by incorrectly assuming that the data collections occurred at different times, while it was, in fact, the same data collection as indicated in the article. There was no deception to study participants nor to the Institutional Review Board for Human Subjects. We don’t believe our informed consent was deceptive because we based our protocol on the best scientific literature available at the time, in 2010. All study participants underwent physician evaluation and follow-up assessments as needed. No ethical principles were disregarded on our part and a thorough review was conducted by the university’s Institutional Review Board for Human Subjects in accordance with the appropriate rules and regulations of the World Medical Association Declaration of Helsinki. We asked our runners to use a gradual transition (according to the Vibram website at the time). We could not find information on increased injury rates in Vibram FiveFingers™ shoes prior to our data collection. In fact, it is our research that brought attention to the potential risks of a too-rapid transition to minimalist style shoes. Towards the end of our data collection a case study was published which reported second metatarsal stress fractures in two runners transitioning to “barefoot-simulation footwear” which appears to be one of the first mentions of potential injury associated with the transition to minimalist style shoes in the literature [1]. However, Giuliani et al. [1] indicated that stress-related changes and fractures in the foot are frequent in runners, generally.

The difference between the number of injuries reported in this study vs. Ridge et al. [4] is simply due to the fact that out of the total number of subjects, only some of the subjects were able to complete a follow-up MRI, while others were able to complete follow-up ultrasound imaging. Ideally, all subjects would have completed all portions of the protocol, but in reality, scheduling difficulties and availability of resources dictated that while most subjects were able to complete both types of imaging testing, some subjects could only be included in the ultrasound analysis while others were only included in the MRI analysis.

Furthermore, it is important to understand the issues involved with defining injury with regard to bone marrow edema (BME). We used a score of 2 through 4 to denote “injury” on the 0–4 scale [3]. A score of 4 represents a stress fracture while a 2 is indicative of a stress reaction which may very well go undetected by the runner unless they have an MRI. No one knows that a BME score of 2 is definitely due to injury; it may be due to normal adaptive remodeling. We chose to classify it as an injury based on advice from the participating physicians – if they saw a patient with that level of BME, they would have advised the patient to modify their training. Therefore, we chose to conservatively classify a score of 2 or above as an injury, whether the subject felt pain or not.

Mr. Robbins’ statement regarding reduced injury rate due to “vigilance” is incorrect due to the fact that all data were collected prior to the class action lawsuit. The subjects would not have a heightened awareness regarding potential injury when running in Vibram footwear because there was no indication in scientific literature or in the national media of a potential problem prior to the lawsuit being made public. Therefore, vigilance could not have played a role in either of our published articles.

We agree that the barefoot condition will provide the maximum sensory feedback to the body. We also suggest that strengthening of lower extremity muscles is important, including strengthening of intrinsic foot muscles. We suggest that improved strength, endurance and motor control of lower extremity muscles will allow the body to more effectively utilize the sensory input it receives from the lower extremity. This improved ability to utilize the sensory input, greater motor control and muscular endurance and strength, should, in our opinion, help decrease injury rates in runners.

We, the authors of both articles, rightly pointed out the potential injury risk during the transition period to the minimalist shoe and consequently have suggested that the transition period should be longer in duration and more gradual and specific in its nature. We appreciate the interest in studying the various functions of the foot and encourage continued lines of investigation to help further our understanding of the important role the foot plays in human movement and function.

• References

• 1 Giuliani J, Masini B, Alitz C, Owens BD. Barefoot-simulating footwear associated with metatarsal stress injury in 2 runners. Orthopedics 2011; 34: e320-e323
• 2 Johnson AW, Myrer JW, Mitchell UH, Hunter I, Ridge ST. The effects of a transition to minimalist shoe running on intrinsic foot muscle size. Int J Sports Med 2016; 37: 154-158
• 3 Lazzarini KM, Troiano RN, Smith RC. Can running cause the appearance of marrow edema on MR images of the foot and ankle?. Radiology 1997; 202: 540-542
• 4 Ridge ST, Johnson AW, Mitchell UH, Hunter I, Robinson E, Rich BS, Brown SD. Foot bone marrow edema after a 10-wk transition to minimalist running shoes. Med Sci Sports Exerc 2013; 45: 1363-1368