Minimal Strikes Back – New Study Muddles the Midsole Debate
by: Ernest Shiwanov
An independent study by PhDs Hannah M. Rice, Steve T. Jamison and Irene S. Davis, published in July 2016’s Medicine and Science in Sports and Exercise, proffered an interesting conclusion. They were seeking a relationship between forces exerted on a runner’s body wearing traditional running shoes landing on their heel or forefoot, versus runners using minimalist footwear but landing on their forefoot.
The big picture reason is straightforward: running-related injuries. As any dedicated runner knows, injuries are part of the process. In search of remedies, some runners shifted away from rearfoot striking on the promise of fewer injuries landing on their mid or forefoot, typically in minimalist footwear. So the researchers asked themselves, what are the links to the type of shoe a runner uses to their foot strike and what are the associated impact?
Noting the absence of literature comparing rear and forefoot strike against traditional and minimalist footwear categories, the authors elected to take a closer look and report their findings. For the manufacturers of minimalist footwear battling it out with maximalist and traditional footwear, the team’s conclusions were encouraging.
Twenty-nine runners jogging at an 8:30 per mile pace (3.13 m/s), were divided into three groups. Two of which were rear and forefoot strikers, using traditional footwear. Traditional meaning shoes with an 11 to 14-millimeter midsole height difference from between the top of the forefoot platform to the top of the midsole’s heel. The other comprised of forefoot strikers running in minimalist footwear (minimalist shoe’s midsole height varies from dead flat or zero drop to 6 to 7 millimeter). For this study, the researchers defined minimalist midsole heights to range from 0 to 4 millimeters.
The groups were divided almost evenly. Ten rearfoot and nine forefoot subjects used traditional gear and 10 wore minimal product landing on their forefoot. The study provided all the participants with the appropriate footwear to match the foot strike and midsole category identified with the runners. Then, all the runners were asked to perform specific running activities to ensure the data would not bias the recorded data. The study did not take various surfaces into account such as pavement or non-paved, gender, conditioning or fatigue effects of their subjects and midsole design attributes (e.g. shapes, densities, flexibility) that could affect some of the measured forces.
The results were both predictable and surprising. Rice, et al, figured the forefoot strikers with the minimal kicks would produce the lowest measured forces of the three groups. That notion was born out by their findings. What they did not see coming was the combination of forces on the groups running in traditional running product would be about the same. In other words, the researchers found almost no difference between the forefoot strikers and the rearfoot strikers running in standard midsole height trainers.
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“Those who habitually run in full minimal shoes had lower vertical and resultant load rates than those who habitually run in partial minimal shoes. Additionally, only those running in partial minimal shoes exhibited impact peaks in their vertical ground reaction forces. This further emphasizes the importance of footwear, and suggests that even being habituated to a small amount of cushioning can lead to harder landings … The results of this study suggest that forefoot striking in shoes with the least cushioning results in the lowest rates of loading,” reports Rice, et al.
The researcher’s conclusions should give pause to adherents of maximalist footwear. Maximal footwear is available in many different midsole drops but is routinely offered in the same range as tested in this study, or 0 to 4 millimeters. Although maximalist footwear has been around for more than five years, it takes time before enough data is collected to see the injury outcomes associated with any type of footwear. Also, the study’s scope did not take into account, several important environmental factors such as training surfaces and midsole design.
Midsoles continue to have major attention paid to them in the pursuit of the elusive perfect transition (a smooth movement of the foot’s pressure path while on the ground before take-off). Although this study adds to sport medicine’s literature, its ruminations suggest more questions than it answered.
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