Froomey’s data

So far, this week has been a good week for us: We could enjoy the road race and individual time trial for both women and men (all spectacular!) and on Monday the scientific paper with the data from Christopher Froome’s test at the GlaxoSmithKline Human Performance Lab in London in August of this year was published (full text available for free here). Some preliminary results were already published by Esquire magazine in December, so much of the data in the paper isn’t coming as a surprise but there are some interesting bits. For a general overview we recommend reading this blog by Alex Simmons and for some light reading read Esquire. We will not repeat what others already said but will cover some other interesting tidbits we found in the article:

1. First we would like to take a moment of silence for the stressful moment that the testers must have experienced when at 11:31 into the maximal test the heart rate monitor failed. Imagine you are testing Chris Froome, one of the greatest grand tour riders ever, and the heart rate monitor fails… Ouch!
2. About his fat percentage of 9.7%: That is 6.7kg of fat with his 70 kg body mass. Sounds high but assuming that most of his (self declared) 3–4 kg weight gain after the TdF is fat, then his fat percentage at 67–68 kg would have been 4.1–5.5%. Which is… low. Just like we would expect.
3. About his gross efficiency: We think it is safe to say that the mentioned increase in gross efficiency from 23.0% to 23.6% is questionable. These numbers are mean gross efficiency over the entire test. So for the second (maximal, hot temperature) test it includes the anaerobic, high intensity part at the end of the test. Of this last part of the test they say in the article (Methods->Gross Efficiency) “..however it should be noted that GE (gross efficiency) data calculated for power outputs above steady state exercise may be influenced by the VO2 slow component and as a result should be interpreted with a degree of caution.“ Meaning: because of the slow VO2 slow component the gross efficiency at high intensities might be higher. In our opinion, this explains the apparent rise in GE. Apart from this fact, it would already be very remarkable if this was true: According to this article (F.J. Hettinga et al. Eur J Appl Physiol (2007) 101: 465) gross efficiency is 0.9% lower in the heat than in normal conditions. We must note however that in this particular study the cold condition was colder and the hot condition was hotter than during Froome’s tests: 15.6°C vs 20°C and 35°C vs 30°C.
4. Chris Froome says that the last time he did exercise testing like this was in 2007. In August 2015 he did two tests (one submaximal, one maximal) 15 minutes apart. It is very well possible that at least part of his increase in performance can be assigned to a learning effect: Doing a test in an unknown laboratory with a face mask is certainly something you have to (and can) get used to.

All in all we are delighted to see that this kind of data from a rider of this level is getting published and we hope that more riders will do this in the future. Follow us here on Medium, Twitter and Facebook.

Author: Aart Goossens. Co-authors: Martijn Veling & Joost Rusche.