A new study from Mass General Brigham, published in PM&R, has added a careful piece of biomechanical evidence to the running world's longest-running open question about advanced footwear technology — whether the carbon-plated, maximally cushioned super shoes that have rewritten the marathon record book are gradually breaking the bones of the people who race in them. The headline finding is not that super shoes are dangerous in any blanket sense, but that they alter two specific running mechanics — cadence and rearfoot eversion excursion — in ways that line up uncomfortably well with the existing risk-factor literature for bone stress injury.
The cohort was small but unusually credible: 11 female and 12 male healthy elite distance runners. Each ran in three shoes — a neutral trainer, a lightweight responsive-foam racer, and an advanced footwear technology shoe with a highly cushioned foam midsole and an embedded stiff plate. The two changes the researchers identified in the AFT condition were a significant drop in cadence (steps per minute) compared to either alternative, and a greater inward arch collapse, captured as rearfoot eversion excursion. Both have their own established association with stress injuries to the metatarsals, navicular and tibia.
That mechanism is not subtle, and it lines up with the case studies that have been accumulating in clinical practice. A lower cadence in a maximally stacked shoe means a longer stride at the same pace, which loads the lower limb differently from a more stride-efficient gait — overstriding, in everyday language. The greater inward foot roll is harder to interpret, but it suggests that the geometry of these shoes — the wide, soft platform with a stiff plate buried inside it — is unstable enough underfoot that some runners are landing on a foot that has more rotational freedom than it would in a stiffer racer.
What the study does not say, and what the authors are at pains to make clear, is that any single training session in a super shoe causes injury. The biomechanical changes they observed are risk factors, not outcomes. The recommendation that emerges sits comfortably with what coaches have been saying for two years: rotate shoes through the training week so that the bones, tendons and connective tissue see different loading patterns; reserve the super shoe for the workouts and races where it actually pays back; and adapt to it gradually rather than swapping in a brand-new pair the week before a goal race. That is not novel advice, but the new study gives it a clean piece of biomechanical scaffolding.
The study lands in the middle of an unusually busy stretch for super-shoe news. Sabastian Sawe's 1:59:30 in London has reframed what is possible in a marathon — every sub-two performance to date has come in a carbon-plated shoe — while the wider retail market has just absorbed the Saucony Endorphin Elite 2's IncrediRUN-foam global retail debut and a wave of Adidas and Hoka launches. The Mass General Brigham paper is a useful reminder that the same technology delivering the world records is doing things to the foot that the people studying running bones still consider worth measuring.