"Beware of those who try to sell you simple answers to complex questions.”
~Scott Adams
Anyone who knows me well knows that I am not what you might call an early adopter. I didn’t get my first cell phone until almost 2005. I still don’t have a Netflix account. I willingly shave with a razor that has only two blades. And when it comes to running shoes, I didn’t buy a pair of wildly popular super shoes until late this past summer. There are many more examples to highlight my old school nature, but I think you get the gist.
Simply put, I tend to take my time with the latest and greatest. Sometimes it’s stubbornness. Though most of the time, it’s that I genuinely like to understand something before I buy into it. Considering how invested I am in running and in runners, you might say I’m really late to the party on advanced footwear technology—but not out of ignorance. I’ve always been wary of hype, especially expensive hype. When hype comes in the form of pricey shoes sold by gazillion-dollar multinational fashion and lifestyle corporations, I think there’s good reason to exercise caution.
Before I was willing to pony up my own money for a pair of fancy shoes, I did what I always do—I combed through the research to make sure the literature actually supports the slogans. While I wasn’t necessarily surprised by what I found, I do think there are a few key insights worth highlighting to help others make an informed decision when it comes to their next pair of advanced running shoes.
In the beginning
Since the Nike Vaporfly 4% debuted ahead of the 2016 U.S. Olympic Marathon Trials, elite races have been dominated by athletes wearing shoes similar to, or even more technologically advanced than, the Vaporfly 4%. Prior to this shift, shoe mass was one of the few footwear characteristics consistently linked to improvements in running economy (RE) and performance. Remarkably, all but one of the fastest 15 men’s and women’s marathon times ever recorded have occurred since the introduction of advanced footwear technologies (AFT), with a similar trend emerging in the half marathon.
Once these shoes became commercially available in 2017, many runners assumed the ‘4%’ translated directly to a 4% faster marathon. In reality, it reflected a 4% improvement in running economy, not necessarily a proportional boost in finish time. Given the well-established relationship between running economy and performance, enhancement in economy via footwear technology has become an active and widespread area of research. Because athletes with similar physiological profiles but better economy generally outperform their peers, even modest advantages from equipment choice may prove meaningful.
Shoe Construction
While the makers of these advanced shoes would argue that there’s more to them than meets the eye, the general makeup of most available AFT models have a few things in common.
- Lightweight construction - Research has consistently shown that adding 100 grams to a shoe's mass increases the energy cost of running by roughly 1%. It’s no coincidence that across brands, these styles of shoes are exceptionally lightweight.
-
Highly resilient and compliant midsole foams - The midsoles of nearly every (perhaps every?) advanced shoe on the market are made of a specific type of foam known as PEBA (polyether block amide). Its unique combination of resilience and compliance is what delivers the greatest performance gains.
- Resilience - The ability of the foam to return to its original shape after being deformed. This returns a significant amount of energy to the runner with each step.
- Compliance - The magnitude of foam compression under impact, which contributes to the soft, cushioned, yet springy feel runners associate with advanced foams.
- A curved carbon fiber plate - The insertion of a stiff and curved plate between layers of foam helps to maximize energy return and reduce energy cost. While many rushed to hail the carbon fiber plate as the real performance enhancer, the advanced foam is really the star of the show.
How long do AFT shoes last?
When athletes are shelling out $300+ for a pair of shoes, it’s reasonable for them to wonder how long these ‘magic’ shoes last. Although opinions differ on the lifespan of AFT, and manufacturers offer little clear guidance, there are a few key factors to consider when deciding whether it’s time to demote your racers to everyday trainers.
- Weight - heavier individuals place greater demands on the foam, causing it to break down faster than it might under the stress from a lighter runner.
- Pace - similar to weight, a faster pace requires more work from the foam, thus accelerating breakdown.
- Temperature extremes, whether hot or cold, will lead to faster foam breakdown. Moderate temperatures both during use and storage may help prolong AFT life.
In general, most experts on material technology suggest a racing shelf-life of anywhere between 100-200 miles, with additional miles available for these shoes to be used as everyday trainers. That said, evidence suggests that after roughly 300 miles, shoes built with a PEBA midsole perform nearly the same as those using traditional materials in terms of running economy. After that, use the same barometer you would for any pair of trainers to decide when to permanently relegate them to grass-cutters.
Do they benefit amateurs as much as elites?
Unsurprisingly, the research on this question is also mixed, but a general theme does emerge. Most evidence suggests that amateurs benefit at least as much as elites, with individual variation existing in both groups. Some studies show that amateur runners benefit considerably more than elite runners, simply because they have far more room for improvement. That said, there is ample evidence to suggest that larger effects are obtained at faster speeds (>16-18 km/hr), suggesting that faster runners may stand to benefit more. In general, most runners are likely to get a performance pop from these shoes.
Is habituation necessary for maximum benefit?
The short answer is maybe. Evidence suggests that getting used to the feel of AFT, especially the characteristic “teeter-totter” effect, can help runners unlock its benefits. Habituation is also thought to be meaningful because of a principle known as the specificity to training, which suggests that runners become most economical when running in shoes that they train regularly in.
That said, some research indicates that wearing less economical shoes (other than to race) could actually amplify the running economy gains experienced when switching to AFT. This thought process is similar to a swimmer holding off on shaving until their most important race, hoping to get the maximum benefit when it counts. I generally recommend that runners, particularly those new to AFT, complete a few longer runs that incorporate race-specific pacing in these shoes. This allows their bodies to acclimate to the changes in force distribution associated with this type of footwear.
In recent years, the question of whether AFT increases injury risk has been raised by athletes, clinicians, and researchers alike. And while the topic could easily warrant a much longer discussion, the honest answer is that we still don’t know how meaningful or benign those risks truly are. Most available research is retrospective, conducted in laboratory settings on treadmills rather than in real-world environments, and is focused primarily on elite male runners, who represent only a small fraction of the people wearing these shoes. I suspect that new research will emerge to offer more insight and guidance on this area of concern in the not-so-distant future.
Keep moving forward!
🚨Have a topic(s) you'd like to learn more about? Reply anytime!
Nothing But Good News
Teams Training for World 'Plogging' Championship-Picking Up Litter While Jogging
A Rare Breed: At 90, This Arlington Heights Runner is an Ultramarathon Man
Recipe of the Month
Vegetarian Split Pea Soup
If your family opted for a ham at Thanksgiving instead of turkey, the non-vegetarian style of this soup would be a great way to make use of any leftovers.
