There's always plenty of talk about footwear flying around the Precision Fuel & Hydration office (Andy and JP I'm looking at both of you) and in the last few years it’s fair to say that the running world has been saturated with, what I’m going to call, “shoe chat” too.
The debate about the development of shoe technology was ignited by World Athletics' decision to limit the impact of Nike’s race-changing footwear ahead of the Olympics in Tokyo...
Why does shoe weight matter?
The Nike Vaporfly 4% shoes became commercially available back in 2017, so runners were suddenly exposed to the possibility of running a personal best simply by switching shoes.
Now, a few years down the line, the results of changing footwear are coming to fruition.
The previously mythical sub-2 hour marathon mark has been broken by Eliud Kipchoge (albeit under specialist conditions), while personal bests across a wide range of distances have been logged, and research - unaffiliated with Nike (or any shoe company for that matter) - has confirmed the four percent average performance benefit.
It isn’t the first time a modification in shoes has yielded a performance-enhancement, but it's the first time we’ve seen an improvement as big as 4-5% (hence the controversy!).
It's hard to pick apart the data and, as much a I'm hesitant to believe such an improvement, it appears there's no getting past the fact that these shoes simply make you faster (or at least more efficient).
If you’re particularly interested in how the Vaporflys improve performance, I’d recommend listening to The Real Science of Sport’s podcast, 'The Shoe That Broke Running'.
Back in the 1980s, researchers working on behalf of Nike conducted the original research investigating the effects of shoe weight.
The group found that adding just 100g (~3.5oz) to the same pair of shoes increased the aerobic demand of running by 1% - a stat you’ll often see when reading up on running shoes and the effect of their weight.
The basic physiology behind this is that the extra weight causes the muscles in the lower body to work slightly harder, which reduces running economy.
An athlete’s running economy is influential when it comes to performance and can be defined as the amount of energy required for a given velocity of sub-maximal running.
The lower the energy demand at a given speed, the greater your running economy. It’s a relatively simple parameter to measure and involves an athlete running on a treadmill at various speeds for anywhere between three and five minutes, whilst simultaneously having their oxygen consumption measured and then finally normalising this for their bodyweight (ml⋅kg⁻¹⋅min⁻¹).
Even a small difference in oxygen uptake can be meaningful to a runner and mount up over long distances, so improvements in running economy are highly sought after.
Taking Nike’s increased aerobic demand 1% finding into account, it seemed clear that the lighter the shoe, the better. With this in mind, you wouldn’t be judged for thinking 'why haven’t we all tossed the running shoes in the trash and started running barefoot?'
Well, because the researchers saw an interesting phenomenon as they continued to experiment with different shoes and different weights. When the weight of the shoe became too light, the energy cost rose again.
It was suggested that the reduction in weight was creating less midsole cushioning in the shoe and, as a result, the runner’s muscles were once again having to work harder to aid the tendons in absorbing the greater landing shock, which in turn increased the energy cost.
Therefore, perhaps lighter isn’t always better?
Do lighter shoes result in faster performance?
Certainly some form of trade-off exists between shoe mass and cushioning. Too much or too little of either can hinder an athlete’s running economy by increasing the muscles’ work. This isn't dissimilar to other huge swings in opinion we see in the sports industry, such as drink plain water to thirst vs drink electrolytes, or all carbs vs no carbs.
A factor which shouldn't be overlooked is the surface an athlete will be running on.
A spongy athletics track will absorb some of the landing shock for you and therefore a shoe with less cushioning is much more appropriate for track running than it is on the hard surface of the road. During road and trail running, where the terrain is far more unforgiving, you’re going to benefit from some added cushioning despite the extra weight that it might add.
So, maybe lighter isn’t always better, but is it faster?
The 1980s findings in the lab were important but without stating the obvious, races are won in the field. So the question that needed to be answered was ‘do heavier running shoes actually translate into slower running times?’.
A 2016 study, published by researchers at the University of Colorado Boulder, investigated exactly that.
They took 18 competitive male runners, all who had recently run 5km in sub-20, and asked them to run three indoor 3,000m time-trials over three weeks, wearing either a control pair of shoes or an identical pair with 100g or 300g of added weight (in the form of small lead pellets stitched into the tongue and side panels).
The athletes were unaware of the adjustment in weight as they were led to believe that they were enlisted to help validate a performance prediction equation using VO₂max (maximal oxygen uptake) and running economy (the study also involved the athletes running on the treadmill the week following the final track session).
To further mask the objective of the study, researchers helped athletes into their shoes to avoid them being handled.
Why? I hear you ask...
A study by Slade et al. (2014) found that athletes were able to perceive small differences in shoe weight if handled but not when worn on their feet. The athletes were told that this helping-on of the shoes was necessary because the small accelerometer attached to the front of the shoe needed to be handled carefully (a clever deception I think you’ll agree).
Out on the track, the results were clear.
Performance times rose by an average of 0.78% per 100g increase in shoe weight, which ties in with what was originally reported in the 1980s Nike experiments.
For the researchers, to see a tangible performance difference in a distance as ‘short’ as 3,000m was quite a surprise and they rightly highlighted the possible implications of their findings - that an elite marathon runner wearing shoes just 100 grams lighter than normal could potentially run roughly a minute faster.
That could be the difference between first and an easily forgotten fourth place finish. And so it was concluded (at this time at least), lighter is faster.
What do new shoe innovations mean for performance?
Since then, the running world has entered a whole new generation of shoe technology.
As mentioned before, the Nike Vaporflys have proven to produce a 4-5% improvement in running economy, depending on the individual.
While a 1% advantage may be argued to be negligible in the grand scheme of competitive running, an improvement of 4% could have huge implications for athletes and race results.
This degree of enhancement has led to passionate debate around what should be allowed in professional running.
This discussion isn’t about the weight of the shoes (although a size 9 ZoomX Next% - Nike’s advancement on the original Vaporfly 4% - does weigh only 190g), it’s about far more.
It's about the about advancements in the foam used - with the newer style foam allowing greater stack height and the inclusion of carbon plates (Nike’s latest ‘next-level’ version, the Nike Alphafly, reportedly contains three!).
Since Nike’s revolutionary shoes burst on the professional running scene, some of the biggest improvements in performance times in history have been seen.
At the Chicago marathon in 2019, Brigid Kosgei knocked a huge 81 seconds off Paula Radcliffe’s previously 'untouchable' 2003 time (2:15:25), as she clocked a jaw-dropping 2:14:04 and became the new world record holder for women running in a mixed-sex marathon race.
This was the single greatest improvement in a previous marathon record since 1967 and a personal best for Kosgei by over four minutes.
This remarkable performance came just a day after Eliud Kipchoge broke the 2-hour barrier running in the assisted race in Vienna.
Both athletes sported a pair of Nike’s latest innovations for these impressive feats - Kosgei in the Next%'s and Kipchoge debuted the Alphaflys (which were reportedly designed around him specifically).
And such examples of dominance have been a pretty consistent trend across the podiums of all of the major marathons in the last couple of years.
In 2019, 31 out of 36 podium positions in major marathons were athletes sporting some version of the Nike shoes. It could be argued that Nike simply sponsor the best athletes, but in the 13 months prior to Kipchoge breaking the 2-hour barrier, the five fastest marathons in history were run by athletes wearing the Nike ZoomX Next%’s.
Whether we like it or not, we’re entering an era of improvement in running performance due to new innovation in shoe technology, so what was once a world-class marathon time is now simply a good marathon time. Records we once thought could never be achieved, are now attainable and breakable.
How have shoe innovations been affected by World Athletics' regulations?
World Athletics have been accused of sleeping on the issue for the past couple of years, while Nike-sponsored athletes have been benefiting from an unfair advantage.
As is to be expected, other shoe brands have been racing to catch up and New Balance, Saucony and Hoka have already produced a similar performance-enhancing shoe - but with Nike having filed certain patents, it’s unclear how much the gap can and will be bridged.
In the next few years, the running world has to try and get to grips with the rapidly advancing technology of shoes and decide where it sits on the issue. The argument of what’s ‘fair’ seems to be the main sticking point. World Athletics have big decisions to make and we don't foresee everyone being happy.
The shoe technology debate is going to run and run.