For decades, running shoes were rated by Runner’s World magazine and other organizations largely on their ability to absorb shock. As a result, manufactures made heels and soles increasingly thick to rank highly in the ratings. This led to shoes that were quite bulky and thickly padded. In a countermovement to this trend, and inspired by a track coach who included barefoot running is his training programs, Nike came out with the first of the modern minimalist shoes, the Free, in 2004. This lightly-padded shoe was only intended for occasional use, not full weekly mileage.
Proponents of minimalist running shoes say that, because of their light cushioning, people running in them alter their gait to lessen shock. Such changes include landing on the midfoot or forefoot rather than the heel, shortening the stride, increasing stride frequency, and lowering peak impact force. This is claimed to reduce this risk of tibial stress fracture, plantar fasciitis, and other overuse injuries, and to strengthen the feet. Biomechanical testing has verified that Africans who grow up running barefoot strike the ground with only a third of the impact experienced by U.S. runners in shoes. Lightweight shoes also lower the energy cost of running, so a runner can go at a faster pace at the same level of exertion, which translates into faster race times. However, running experts have cautioned that any switch from heavily cushioned standard running shoes to minimalist shoes must be gradual in order to allow the muscles, bones, and tendons of the foot and leg to adapt.
The minimalist running shoe movement accelerated significantly with the publication of the 2009 book, “Born to Run,” which revealed that the Tarahumara Indians of northern Mexico get fewer injuries than U.S. runners even though they wear very thin rubber sandals and run extremely long distances. Manufacturers other than Nike came up with their own versions of minimalist shoes. Vibram, an Italian company, introduced its Five Fingers model, in which each toe is individually gloved. It weighs a scant 5.7 oz and has a heel thickness of only 7.2 mm (compared with up to 38 mm on heavily padded “cushion” or “motion control” shoes). This model is now the leader of the minimalist shoe market.
Other running shoe companies have jumped on the minimalist bandwagon. Saucony came out with its Kinvara model, which has somewhat more protection than the free and is intended for regular, rather than occasional, use. New Balance will debut its Minimus in February, which the company says will give a free-foot feel but still have cushioning in key spots. Merrel will put out its Barefoot Collection in February with a sole from Vibram and a very light upper. Also in February, Nike will supplement it Free line with its Lunar Eclipse lightweight stability trainer. Addidas will introduce a light, fast, everyday shoe in the Fall of 2011. Other companies that do not plan to introduce minimalist shoes have been making their existing models lighter and more flexible. Yet there is concern within some shoe companies that runners may switch to minimalist shoes too rapidly and subject themselves to injury.
An important factor in how long it takes to adapt to a minimalist shoe is the difference in thickness between the forefoot and heel padding. It can range from zero for a shoe with no difference between the thickness of heel and forefoot padding, to a 12 mm greater thickness of heel than forefoot padding. If one has been accustomed to running in a heavily padded shoe with a large difference between the padding thickness of heel and forefoot, the adaptation time to a minimalist shoe should be considerable.
As of now, there have been no published articles comparing the injury rate of runners wearing minimalist shoes vs. those training in standard shoes. However, many of the runners who have switched to minimalist shoes swear by them. Yet few market watchers expect such shoes to ever capture a major share of the running shoe market. Currently, no more than 10% of running shoes sold could be called minimalist.
While few studies have been done on minimalist shoes, evidence suggests that such shoes do alter running gait so as to reduce the degree of foot-strike impact and also allow the foot to flex in a natural manner while in contact with the ground. However, since most Americans have grown up walking, running, and playing sports in supportive shoes with heels more thickly padded than forefeet, the adaptation to relatively flat and lightly padded shoes can be difficult and potentially injurious. Additionally, such shoes offer little protection against foot injury that can occur when stepping on a rock, tack, or other object. Those who are willing to accept the risk of trying such shoes should do so with caution and increase the weekly mileage they run in them very gradually. It remains to be seen whether the benefits of minimalist shoes outweigh their risks.