NEW YORK - Advocates of trendy "minimalist" running shoes promise a more natural experience, but runners in a new study reported higher rates of injury and pain with the less structured shoes.
Three months after switching from traditional running shoes to the minimalist variety, study participants had two to three times as many injuries compared to runners who stuck with traditional shoes.
Minimalist footwear is designed to provide as little interference to the runner as possible, study author Dr. Michael Ryan of Griffith University in Australia said.
"Some models are really just conventional running shoes without additional stability elements, while others are so minimalist that they are essentially a 4 millimeter thick rubber glove for your feet," he said.
Biomechanical studies in laboratories indicate that running barefoot, or close to it, shortens a person's stride, causing joints to flex less and theoretically leading to fewer injuries.
For the new study, 99 adult runners in Vancouver, Canada, started a three-month training programme in preparation for running a 10-kilometer race. They had never tried barefoot running or minimalist running before.
A third of the participants were given so-called partial-minimalist running shoes, or a full-minimalist shoe with separated toes.
The final third got a traditional structured running shoe, for comparison.
Of the 23 injuries that happened during the training period, four were among the runners wearing traditional shoes, 12 among those wearing partial-minimalist shoes and seven in the full-minimalist shoe group.
Runners using the full-minimalist shoes also reported higher rates of shin and calf pain than the other participants.
"This study supports what I and others have been arguing for years," Daniel Lieberman, author of widely cited studies comparing barefoot running to running with shoes, told Reuters Health in an email.
"If you switch to minimal shoes or go barefoot you need to (a) do so gradually so your body can adapt, and (b) you need to learn proper running form," said Lieberman, who is chair of Human Evolutionary Biology at Harvard University in Cambridge, Massachusetts, and not involved in the new study.
But, Lieberman told Reuters Health, he would not go as far as calling minimalist shoes "worse" than conventional shoes, at least not based on this study.
The runners did not transition gradually, the study did not examine their running form, and it only included the initial transition period to the new shoes, which many runners would adapt to over time, he said.
"What matters most for injury is how you run, not what is on your feet, and this study only looked at the latter," Lieberman said.
In their report, published in the British Journal of Sports Medicine, Ryan and his colleagues speculate that the runners who switched to full-minimalist shoes may have been forced to change their running form, and that might account for the highest injury rate being seen in the group wearing partial-minimalist shoes.
"The injures these people had were calf muscle strains and Achilles tendonitis, both temporary injuries one expects to encounter while transitioning and which the body can and does adapt to," Lieberman said.
Ryan said runners should not be discouraged from trying minimalist shoes based on his group's results.
"Runners need to be aware of the risks when running in minimalist shoes, but I still think this footwear category has a big role to play in improving the quality of running form and potentially reducing injury risk in the long term with proper guidance from an experienced running coach or medical professional," he said.
Runners should take time to break in their new shoes before running in earnest, David W. Jenkins, professor at the Arizona School of Podiatric Medicine of Midwestern University in Glendale, said.
"If one is to begin running in minimalist footwear, one needs to break in the new footwear for many weeks before training in earnest," Jenkins told Reuters Health in an email.
"Some sources have suggested at least 6 weeks and what I suggest, break them in for a few weeks just walking around before even attempting to wear (them) running and then do the slow 6-week build up in miles," he said.