Minimalism is dead, but this paper is VERY interesting!

So much research has now been published on the minimalist fad now that I barely glance at anything related to it. This recent paper however, made me stand up and pay attention..

The influence of minimalist footwear and stride length reduction on lower-extremity running mechanics and cumulative loading. Ferminger, C.R., Edwards, W.B., Journal of Science and Medicine in Sport Volume 19, Issue 12, December 2016

So, what is new and different about the findings of this study?

Well for a start, they did not just look at footwear. This was a Within-subject study where subjects attended a 2 hour data collection session at the University of Calgary's Human Performance Laboratory. Motion capture, force platform, and plantar pressure data were collected as participants ran overground at their preferred running speed for 10 trials at each of four conditions:

(1) control shoe at preferred stride length;

(2) control shoe at 90% preferred stride length;

(3) minimalist shoe at preferred stride length;

(4) minimalist shoe at 90% preferred stride length.

Fourteen young healthy males ran overground at their preferred speed while motion capture, force platform, and plantar pressure data were collected. Peak moments, impulse, mechanical work, and cumulative impulse were calculated at the metatarsophalangeal, ankle, and knee joint, and compared between conditions using a 2 × 2 factor repeated measures ANOVA.

The control (i.e., traditional) shoe was a New Balance 890v5, weighing 8.6 oz with a 19.0 mm heel profile and 11.0 mm toe profile. The minimalist shoe was a New Balance Minimus Zero v2, weighing 5.9 oz with a 12.8 mm heel profile and 12.0 mm toe profile.

Now the reason this study is interesting is because this is the first study to my knowledge where stride length was examined as an intervention, rather than a consequence of, the shod condition.

What did they find?

Well..

In general, running in minimalist footwear increased measures of loading at the metatarsophalangeal joint and ankle joint (mean increases of 7.3% and 5.9%, respectively), but decreased measures of loading at the knee (mean decrease of 7.3%).

1-s2.0-S1440244016000712-gr1.jpg

Trial-averaged MTP, ankle, and knee joint moments and powers for a representative subject running in the control and minimalist shoe at PSL. Negative MTP/ankle moments represent plantarflexion. Negative knee moments represent flexion. Positive and negative values of power represent generation and absorption, respectively. Shaded areas are ±1 SD.

Absolutely no surprises here, this is in keeping with a mountain of other work which all agrees. The outlier  is the measured increased loading on the MPJ (in essence the 1st MPJ:  The MTP joint axis was defined by a line connecting the first and fifth metatarsal head markers, and the MTP joint moment calculation was considered valid only after the COP was distal to the joint axis). This now give us a big clue toward the avalanche of MT stress fractures we saw at the height of the barefoot/minimalist craze.

Conversely,

running with reduced stride length decreased single-stance measures of loading at the ankle and knee joint (ranging from −0.9% to −20.5%), though cumulative impulse was higher at the ankle and lower at the knee.

The study therefore concluded:

“Running in the minimalist shoe increased joint loads at the MTP and ankle joint, which may help to explain some of the incidence of overuse injuries observed in minimalist shoe users. A 10% reduction in stride length decreased loads at the ankle and knee, but cumulative loads were only lower at the latter joint. Reducing stride length was more effective at decreasing knee joint loads than the minimalist shoe, but both load reduction mechanisms appear to have an additive effect.”

OK.. roger that, so what are the practical implications of this study?

1.       Minimalist shoes decreased knee joint loads but increased ankle and MTP joint loads.

2.       A 10% reduction in stride length reduced knee and ankle joint loads.

3.       Reducing stride length was more effective at decreasing knee joint loads than the minimalist shoe, but in combination appear to have an additive effect.

So the bottom line is another cross against minimalist footwear and another tick against gait retraining.

Worth thinking about…

Simon Bartold
Director of Bartold Clinical

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