Like a first kiss, the first time you experience running in a carbon plate running shoe is something that lingers long in the memory. I remember getting the original Nike Vaporfly 4%, which at the time was pretty much the only carbon plate shoe on the market (unlike now where most brands have several in their line ups). The 4% referred to the average measured improvement which studies showed in running economy. It was like strapping two jet packs to my feet. Having only worn regular midsole shoes before, these shoes felt like the equivalent of putting on the Batsuit or Superman's cape, granting upon the wearer the ability to run fast for seemingly much less effort.
This was 2018. What followed has single handedly transformed the sport of running and athletics in general, sending world records crashing and elevating performances for amateurs and elites on the track and the road, across all distances.
They are incredibly fun to run in, the propulsion and 'pop' giving you maximum reward for your effort, and weighing next to nothing, they invite you to fly.
I am an unashamed fan, like most (if not all, there are some holdouts who prefer to remain, shall we say, low carbon :-) runners, and if I'm racing tomorrow, you'd better believe that I'm packing my Vaporflys.
And yet, I am wary about their proliferation and what they might mean for training, performance, and foot health.
But first, let's just remind ourselves what they actually are. The use of carbon plates in running shoes did not start in the mid-2010s. In fact the breakthrough in terms of technology was not the invention of the carbon plate, but rather in that other material more commonly found in running shoes: foam. More specifically, the advancement of polyether block amide (PEBA), which can be compressed at greater density, offering stiffness as well as cushioning and responsiveness. In combination with a carbon plate, advancements in which enabled it to become more curved and therefore able to act as a 'lever', this creates the inimitable propulsion.
If it all sounds a bit, well, mechanical, then that's because it is. It may not feel obvious, but on very minor levels, these shoes are providing our feet with tiny supports which are causing us to run in a way that is quite unlike our natural footstrike. This is not to fetishise the 'barefoot' running trend that took off in the early 2010s. But I have long suspected, based on my own experience and anecdotally from others, that overuse of carbon plate shoes can lead to problems elsewhere. For some, it's the stiffness of the shoe itself, which doesn't allow the foot to do it's natural flex with every step. For others, it's the aggression of the 'rocker' which causes runners to tip further forward on their foot and place more pressure on that part than it can cope with. I've heard of some runners having problems with their achilles, the whip of each step causing the tendon to become overloaded.
This is now becoming the focus of researchers. It's early days and the research is patchy, but there are signs that there is evidence now to back up my view. A paper in Sports Medicine, entitled "Bone Stress Injuries in Runners Using Carbon Fiber Plate Footwear" presents a case series of navicular bone stress injuries in runners training in these shoes, from a range of running backgrounds.
Like I said, I'm not retiring my carbon plate racers any time soon (have you seen how much they cost? Even if I wanted to, I'm not into throwing money down the drain!). I believe that for racing, especially now, if you are competitive then you are disadvantaging yourself if you decide not to race in a pair. The phrase 'mechanical doping' feels harsh and perhaps unfair in a sport which, like most sports, has used technology to evolve. But if doping is the presence of a factor that makes those who have it almost impossible to be defeated by those who don't, then it's not completely unreasonable.
I do believe however that racing aside, it's better to stick to non-carbon plate shoes, or at the very least, limit their use to a maximum of twice a week. This might be a key session where you want the confidence boost of hitting a certain pace, for example a marathon pace run. But otherwise, using them sparingly means that when you are doing workouts in non-plated shoes, you know that you have a special factor that you can introduce on race day and really feel the benefit of that uplift. And by using non-plated shoes, particularly a rotation of them each with slightly different drops, shapes, midsoles, you are contributing to the ongoing development of your foot strength and above all, health. In doing so, you're even more likely to get that 4% (or beyond) improvement.
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