By Daniel Brayson, @drdanbrayson
SPIN cycling festival, a celebration of all things cycling, took place on the weekend of 12 May 2017 at the Olympia in Kensington, London. Here at The Physiological Society, we thought it would be the perfect opportunity to showcase the wonders of physiology, using funding from The Society’s Public Engagement Grants.
The premise of our activity was to find some anecdotal dogma, which is prevalent in sports like cycling, and disprove it. Put simply, we went on a myth-busting mission.
A popular assumption among amateur cycling enthusiasts is that it is good to cycle at a high cadence. Discarding the jargon, this essentially means pedalling really fast. Many people think this because successful professional athletes such as Chris Froome, and previously Lance Armstrong, cycled at very high cadences when they were racing in huge competitions such as the Tour de France, the most famous cycling race in the world.
We based our experiment on a paper in one of The Society’s journals, Physiological Reports, from 2015 by Formenti and colleagues titled Pedalling rate is an important determinant of human oxygen uptake during exercise on the cycle ergometer. What the paper essentially showed is that the faster you pedal for a given work rate, the more energy you use.
Bike like the wind
With this in mind, we set out to perform some live experiments on festival-goers. We set up a bike on a smart turbo trainer with a computer that we could use to read measurements. We recruited many willing volunteers over the course of the weekend, fitting them with a device to measure heart rate, and setting them up on the bike.
Using the smart turbo trainer, we set the amount of work that the volunteers would do to 150 watts of power and placed headphones on them. They then sat for 1 minute before beginning to cycle in time with a metronome, or a clicking sound, that was playing through the headphones. We changed the speed of the click at set intervals which meant that the volunteer would change their cadence accordingly. At each cadence, we recorded the heart rate of the volunteer twice, 30 seconds apart.
Pedalling faster, beating faster
We found that as pedalling rate increased, so did heart rate. This can be seen on the left-hand graph below by the line which goes up in diagonal from bottom left to top right. This suggests that faster pedalling did indeed require more energy, even though the power output remained constant.
Our graph, on the left, comes to a similar conclusion as Formenti and his colleagues on the right. As pedalling rate goes up, so does work rate and energy expenditure. Where Formenti measured oxygen uptake, which requires unwieldy equipment unsuitable for our event, we used heart rate as an easily obtainable proxy measurement, and it agrees nicely with Formenti’s findings.
What does it mean, really?
The real world meaning here is that cycling along the road in lower gears than necessary with high pedalling rate uses more energy than cycling in slightly higher gears but pedalling at a slower rate.
So what’s the deal with Chris Froome?
Chris Froome, and other pro cyclists are not your average human beings from a physiological perspective, so it’s probably a bad idea for us to copy them! The science does show that pedalling quickly at sustained power outputs up to 400 watts, achievable mostly by elite athletes, is far less wasteful. This is because most of the energy gets transferred to the bike in this scenario.
It was especially dynamic and rewarding to engage with a diverse mix of people and preach the gospel of physiology. I would like to thank all the visitors who staked their reputations by joining our experiment! I would also like to thank The Physiological Society for financial support and especially Anisha Tailor for all of her sage advice. A big thanks to Louis Passfield for his generous support and loan of equipment. Finally, I would especially like to thank all of my wonderful volunteer scientists without whom the whole event would surely have been a disaster Elizabeth Halton, Chris Fullerton, Ozama Ismail, Fulye Argunhan, Elena Wilde, Svetlana Mastitskaya, Xiao Xiao Han, and Nick Beazley-Long.