Sometimes I struggle to decide what to include as the title of a blog post; this time is no exception. Should I title this post: “Minimalist Running Shoes Increase the Achilles Tendon Load” or should I title it “Maximalist Running Shoes Decreases the Achilles Tendon Load“? (I played with the headline concept before, here). Either title would be appropriate as that is what this research showed:
Effects of minimalist and maximalist footwear on Achilles tendon load in recreational runners
J. Sinclair, J. Richards, H. Shore
Comparative Exercise Physiology; Published Online: October 27, 2015
The current investigation aimed to comparatively examine the effects of minimalist, maximalist and conventional footwear on Achilles tendon forces (ATF) during running. Twelve male runners (age 23.11±5.01 years, height 1.78±0.10 cm and body mass 77.13±7.89 kg) ran at 4.0 m/s in the three footwear conditions. ATF’s were calculated using Opensim software allowing the magnitudal and temporal aspects of the ATF to be quantified. Differences between footwear were examined using one-way repeated measures ANOVA. The results showed the peak ATF was significantly larger in minimalist footwear (5.97±1.38 body weight (BW)) compared to maximalist (5.07±1.42 BW). In addition it was revealed that ATF per mile was significantly larger in minimalist (492.31±157.72 BW) in comparison to both maximalist (377.31±148.06 BW) and conventional (402.71±125.51 BW) footwear. Given the relationship between high ATF and Achilles tendon degradation, the current investigation indicated that minimalist footwear may increase runners risk for Achilles tendon injury.
This study took 12 recreational runners and had them run in the New Balance 1260v2 (conventional), the Hoka One One (maximalist) and the Vibram Five Fingers (minimalist) and did some kinematic and kinetic measure to determine loads in the Achilles tendon in the different footwear conditions. The loads were higher in the minimalist shoes. There was no difference in the Achilles tendon loads between the conventional and maximalist running shoes.
The authors commented on the finding:
“This observation is clinically important regarding the etiology of Achilles tendon pathologies in runners and appears to refute the notion that minimalist footwear may unanimously reduce the incidence of chronic injury … Therefore, the findings from the current investigation indicate that minimalist footwear may place runners at a greater risk from Achilles tendon pathology”.
Nothing in the design, methods and analysis jumps out at me as being problematic. Adequate information was provided to make that judgement. This was an acute intervention and the participants were not habituated to the difference footwear conditions and some may have an issue with that.
The sample size of 12 is bound to be raised by some who do not like the results of the study (yet they would have been happy with that sample size if they liked the results), but I rarely dismiss a study based on sample size. In the above case, it was a repeated measures design in which you generally can get away with smaller sample sizes and the results were statistically significant, with the p value telling us the probability of getting the same result in the larger population. In this case, it would be unethical to use a larger group.
As always, I go where the evidence takes me until convinced otherwise…and this study tells me that minimalist shoes increase the loads in the Achilles tendon.
Sinclair, J., Richards, J., & Shore, H. (2015). Effects of minimalist and maximalist footwear on Achilles tendon load in recreational runners Comparative Exercise Physiology, 1-6 DOI: 10.3920/CEP150024