Carbon Plated Running Shoes... Flying Machines or Overpriced Daps?
We caught up with Matt Hart – Senior Podiatrist at ACE Feet in Motion to get his perspective on the science behind the debate.
Running shoes are often advocated as an important requirement for distance running and according to studies has been suggested as an extrinsic factor that can influence running performance. Research shows us that greater shoe cushioning, increased longitudinal bending stiffness through use of carbon plates and reduced weight all positively influence running performance.
Since the 2017 Nike Breaking 2 project in which the world was introduced to the Nike Vaporfly 4%, a shoe which was lightweight, had a significantly thicker midsole foam, embedded with a carbon fibre plate we have seen, in comparison to traditional race shoes, significant improvements in distance running race times.
Since 2018, using an updated version of the original Vaportfly 4% we have seen; Eluid Kipchoge shave 78 seconds off the men’s marathon record that stood for four years; Brigid Kosgei smash Paula Radcliffe’s 16-year standing women’s marathon world record in 2019; Geoffrey Kamworor break the men’s half marathon world record and in 2020 Ababel Yeshaneh break the women’s half marathon record.
This wave of record breaking performances has sparked debate around the potential benefit of these shoes, with many believing that without these shoes they would be at a disadvantage due to the carbon plate acting as a spring, aiding in forward propulsion of the runner. However, research has disputed that the carbon plates are solely responsible for the spring like action, pointing out that development of the midsole foams and their advancement in energy return properties that the midsole might be more responsible for the spring like action.
Welsh Athletics middle-distance athlete Jenny Nesbitt had the following praise for carbon plated running shoes:
"The advancement in shoe technology over the past few years has been incredible. To think that when I ran my first road race, I was wearing the most minimal shoe I could find, with no cushion or a carbon plate. Now the return I get from my carbon plated shoes is a game changer. From being able to recover better in workouts, to being propelled forward in races. The shoes have really changed the landscape of the sport, for both good and bad and I would not be surprised to see this new era of world records continue!"
The polyamide block elastomer (PEBA) foam material used in the new racing shoes is a highly compliant but resilient foam, which according to the research provides greater cushioning without incurring the energetic penalty of added weight. Research has shown greater improvements in running performance at speeds of 16-18kph with a 2.8-4% reduction in the energetic cost to running compared with running speeds of 11-14kph where only a 1.4-2% reduction was observed when compared to shoes using a thermoplastic polyurethane (TPU) or ethaline vinyl acetate (EVA) cushioned midsole. It appears running speed may therefore influence the performance benefits of these shoes.
When it comes to the location of the carbon plate, an embedded (in between midsole foam) curved plate seems to have the most influence on running performance. It is suggested that increasing the overall midsole bending stiffness may delay or reduce performance deteriorations during prolonged running, potentially delaying the onset of fatigue related changes. Rather than the plate acting as a spring it seems to aid in minimising the energy lost at the metatarsal-phalangeal joint through reduced joint dorsiflexion and energy absorption during the stance phase, improving overall energy return.
The combined effect of the highly cushioned midsole and embedded carbon plate have shown to decrease stride frequency and increase stride length. Both parameters are mutually dependent, defining running speed and according to current research a reduction in stride frequency is likely to bring about an increase in stride length, which, if speed is maintained is likely to have a positive influence on distance running performance.
As with all new technology it is important to remember that differences in midsole foam compliance, resilience, and geometry (stack height and toe spring) can influence running performance both positively and negatively, which can further be impacted with individual differences in a runners characteristics such as shoe size, body mass, and strike pattern. This suggests that even though we see significant improvements in race times when wearing these shoes, there will always be responders and non-responders to high cushioned shoes and increased midsole bending stiffness at varying running speeds.
Adam Rattenberry MSc PgC MCSP HCPC, Lead Performance Physiotherapist & Athlete Services Manager at Welsh Athletics commented:
“The use of carbon plated shoes should be considered by everyone, but like any trainer, some are more suited to their uses than others. We recommend that carbon plated shoes be used as a performance or competition shoe, as anecdotal data suggests an increase in foot, ankle and shin injuries, if carbon plated footwear is used frequently. We wouldn’t recommend a carbon plated trainer as your everyday running trainer. However, there are no hard and fast guidelines on the use of this type of footwear. The research world is still trying to understand the effects of the carbon plate on injury prevalence and it will be several years before any longitudinal data on injury prevalence is discovered.”
Charlotte Arter, middle-distance Welsh athlete added:
“Carbon shoes definitely have their advantages and I absolutely love to lace up my ASICS metaspeed sky to race any distance on the road. However, I only save these for race day as they have a full carbon plate. So to help reduce the risk of injury, I wear the ASICS metaracers for my two sessions a week as they just have a carbon midsole plate and feel a bit like an old school racing flat but with a bit of carbon in them. All in all, carbon shoes definitely have their place in training, but for me I use them sparingly and save the real benefits of them for racing!”
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