Running on carbon
While carbon is prevalent in the cycling industry since a long time, carbon fibers weren’t found much in running shoes until the very recent developments, starting with Nike’s breaking2 project. I got converted in 2018 already, when I acquired a pair of the Vaporfly 4% FlyKnit shoes that I wore during the IM Barcelona. Recently though, a lot more offering came to the market, with the likes of Saucony (whose Powerrun+ foam I really liked in the Triumph17 and Freedom3 training shoes), NewBalance (whose fit is slightly less well adapted to my feet), Adidas (finally with a worthwhile replacement for Boost? I still miss my original Supernovas of 2016…), Hoka (not a super fan of the low drop options), or Brooks (which I stopped buying after the disappointment of the Launch4).
While marketing got involved, upping the prices and (artificially?) limiting availability, I still managed to acquire a pair of Saucony Endorphin Pro and Nike Alphafly Next% (would have loved to try the Adios Pro as well, but couldn’t find it). The feeling is a little different between the two pairs, with the Endorphin more traditional, and the Alphafly giving a very distinct sensation of being different. Both do feel like they make it a little easier to hold a tempo pace, and have the legs recover faster after a hard race (especially calves, there could be a little more strain on the harmstrings though).
Me running the first 2k with the Reeboks. Notice the smartphone on the biceps, beeping every 10s (50m) to ensure exact pacing.
In order to check on those sensations, and try to see which shoes is better for me, I decided to run a quick test on the track with Jamie. Plan: 4x 2000 m on a fast pace, that builds a little bit of lactate, but not all-out session either. I opted for 3’20/km pace, which sits between my 10 km and half-marathon pace. Shoes to be tested: a training shoe (to have a baseline), the Reebok Floatride Forever Energy, which is a very nice training shoe, but I would never wear in a race. An old-school racing shoe, the Nike Streak 7, which is close to my choices up until mid-2018, and likely still now up to 5 km races. Then the Endorphin and finally the Alphafly. I picked the order training -> old-school -> new gens in order to avoid attributing any potential trend to fatigue during the session.
Results: (updated with weigths according to comment by David)
|Shoe||Weight (pair)||Lactate||Heart rate||Feeling|
|Reebok Forever Floatride||569 g||4.3 mmol/l||175 bpm||hard|
|Nike Streak 7||423 g||4.0 mmol/l||176 bpm||ok|
|Saucony Endorphin Pro||457 g||3.4 mmol/l||175 bpm||easy|
|Nike Alphafly Next%||506 g||3.5 mmol/l||173 bpm||easy|
Top: Streaks, Endorphins, Alphaflys (left to right). Bottom: Performance&Joy's lactate measurement device.
Obviously, much better tests could be devised, but the decrease in lactate confirms my feelings of having in my hands a new generation of shoes that are a significant improvement over the old-school light and thin ones. Heart rate is likely not really dropping because of the heart rate lag and fatigue acquired during the session (when I don’t change shoes, the heart rate steadily increases from one repetition to the next at constant pace).
Distinguishing the two carbon-plated shoes is not within the quality of this quick test, which probably means I’ll use the one that I prefer the feeling of (if you feel confident, you’ll be fast). Not so clear yet to me, since the Alphafly gives me this mental boost of being something different, while the Endorphin is kind of a traditional shoes that you forget, which means the feet response is more intuitive. I may also change which pair I wear depending on the terrain or type of race.