In 2010, the running-shoe world was in turmoil.
The rapid rise of barefoot and minimalist running had sparked a critical re-evaluation of all the fancy technology packed into the most popular shoes – rollbars, heel lifts, cushioning systems and so on. The evidence that these features actually helped reduce injury rates, it turned out, was practically non-existent.
The bold promises made by minimalist shoe makers, meanwhile, were equally unsupported. Same for subsequent trends such as super-cushioned "maximalist" shoes. What was needed, everyone agreed, was high-quality research: randomized, double-blinded, placebo-controlled trials of different shoe features.
These things take time, but the ambitious research projects launched in the wake of that turbulent period are finally generating results. The answers they provide don't reveal any universal truths about the best running shoe, but they offer some interesting insights that might help you find one that works for you.
Some of the most careful and methodical research comes from a small group in Luxembourg, led by Laurent Malisoux, a frequently injured ex-volleyball player. While many studies have pitted different types of shoes against each other, Malisoux and his colleagues in the Sports Medicine Research Laboratory at the Luxembourg Institute of Health put their volunteers in specially manufactured shoes that are identical in every respect except for the one key feature they want to test.
Their most recent study, published last November in the American Journal of Sports Medicine, tested the effect of heel-to-toe drop, which is the height difference between the back and front of the shoe. While conventional running shoes tend to have relatively big drops of 10 millimetres or more, minimalist running advocates have argued that "zero-drop" shoes promote a more natural and injury-proof running stride.
Working with the French sporting goods company Decathlon, which produces a line of running shoes under the Kalenji brand, Malisoux issued generic shoes to 553 runners, with either a zero-, six-, or 10-millimetre drop. All the shoes had at least 14 millimetres of cushioning throughout the sole and the participants reported their training and injuries online over the next six months.
The results showed … nothing, basically. A quarter of the participants reported some form of injury, but there were no significant differences between the different heel-to-toe drop groups.
A closer look at the data suggested that occasional runners might have suffered fewer injuries in the low-drop shoes, while regular runners might have suffered more injuries when forced to switch from their usual high-drop shoes to the low-drop option – a finding that, if confirmed, would be consistent with the prevailing idea that sudden changes in shoe type are particularly risky.
On a related note, an earlier study by Malisoux and his colleagues found that runners who regularly switched back and forth between two or more different types of running shoe were almost 40 per cent less likely to suffer an injury, perhaps because the impacts and loads were slightly different with each shoe.
For decades, runners have been encouraged to buy shoes according to their foot type; those whose feet overpronate, or roll too far inward with each stride, are assigned motion-control shoes, which typically include some rigid plastic in the insole to limit pronation. But as debates about natural running and the role of shoe technology intensified earlier in the decade, this theory was challenged – and there seemed to be no reliable evidence that the technology reduced injuries.
Malisoux's study assigned 372 runners to identical shoes that differed only in the presence or absence of motion control, and again followed them for six months. The results, published last April in the British Journal of Sports Medicine, were clear: runners who received the motion-control shoes were 45 per cent less likely to suffer an injury.
Moreover, this difference was almost entirely because of the effect observed in runners diagnosed (using a method called the Foot Posture Index) with a pronated foot. Runners in this subgroup were a remarkable 66 per cent less likely to be injured if they were assigned motion-control shoes.
Such findings, after years of acrimonious debate about the role of shoe technology, seem explosive. And yet, says Amby Burfoot, an editor-at-large at Runner's World magazine, few in the running world seem to have noticed.
"Even though the minimalism fervour has largely faded," he says, "many of us seem to have concluded that we can't expect a lot of miracles like injury prevention from our shoes."
Even shoe companies, chastened by past controversies, have become more circumspect about boasting that their shoes prevent injuries, Burfoot says. In 2014, Vibram USA, which makes the iconic FiveFingers minimalist shoe, agreed to pay $3.75-million (U.S.) to settle a class-action lawsuit about its injury-reduction claims.
Still, Malisoux's studies offer some guidance for those who want to run in conventional cushioned shoes. His advice: if you're using cushioned shoes, opt for some degree of motion control. If you've been running happily in a given type of shoe, don't change. Better yet, alternate between two pairs.
And most importantly, follow the advice of former University of Calgary shoe guru Benno Nigg and choose a shoe that feels comfortable on your foot. That perceptual feedback may be the most sensitive assessment tool you've got, Malisoux says: "If the shoe does not fit the foot, it will never work."
Alex Hutchinson's latest book is Which Comes First, Cardio or Weights? Follow him on Twitter @sweatscience