Scientists reveal how pedalling a low gear at a high cadence could waste 60 per cent of a cyclist's energy
Pedalling fast in a low gear wastes your energy, scientists have demonstrated. When you cycle at the wrong cadence most of your effort will go into moving your legs up and down, not moving the bike forward.
“If a recreational cyclist tries to copy the high cadence of a pro but, instead of turning big gears, they ride a low gear, they can waste 60 per cent of their energy,” says Dr Federico Formenti, Senior Research Fellow in physiology at the University of Oxford.
Regular cyclists tend to save their energy instinctively by choosing the most comfortable gears but some clever experiments by Formenti and his colleagues have now revealed why.
They recruited ten volunteers and measured their oxygen consumption while pedalling on an exercise bike (a cycle ergometer) to reveal the power they put into the stationary bike.
At the same time the scientists also took a 3D infrared video of the riders, to calculate how much power the lab rats were using to move their legs.
Watch: Three steps to perfect gear changes
At a low exercise intensity of 50W, they found that pedalling in a small gear at 110 rpm put more than 60 per cent of their power into moving parts of their own body, including thighs, knees and feet while only 40 per cent of it actually went into spinning the cranks. It was a massively inefficient way to ride.
“At this low intensity of 50W it really is very gentle riding, say down a slight gradient or on the flat with the wind behind you,” says Dr Formenti, who cycles to work daily.
In contrast, Chris Froome had a cadence of 97rpm on the climb up La Pierre Saint Martin on stage 10 of the Tour de France last year, where he set up his second yellow jersey victory. He was, though, putting out about 390W through his 52/38 gearing – a far cry from a leisurely roll.
Physiologists know that muscle efficiency all comes down to the speed at which your muscles can contract. If you choose a gear and cadence that allows your muscles to contract at one third of their maximum velocity, you’ll maximise your power output.
The pedalling efficiency evidence from Formenti’s team was actually part of more significant research that could improve how sports scientists estimate energy consumption on stationary cycle ergometers.
Pro cyclists predict their performance with such tests so if they are made more accurate, they could help them ride faster.
But these tests have to rely on a limited set of measurements from a rider and they’re put into an equation to estimate their oxygen uptake (VO2) because it’s an indication of how well their body is performing.
“It’s not feasible to measure directly how much fuel your body uses in exercise so oxygen uptake (VO2) is a good indicator,” says Formenti.
“The conventional equation for doing this is from the American College of Sports Medicine and it includes body mass and external work rate. Perhaps surprisingly for a test done on a bicycle ergometer, the equation ignores pedalling rate.”
Formenti’s team ran its experiments and has shown that, by adding pedalling rate, they can now improve its accuracy of the equation at predicting how well a rider performs when they are working just a little below his or her VO2 maximum.
“We conclude that pedalling rate is an important determinant of human VO2 during cycling exercise and it should be considered when predicting oxygen consumption,” says Dr Formenti.
In some ways it’s yet another case of science explaining what cyclists have learned from experience.
“Cyclists and coaches are well aware of the importance of pedalling rate in cycling,” says Professor Louis Passfield of the University of Kent, who was British Cycling’s lead scientist in preparation for the Barcelona, Atlanta and Beijing Olympics.
“Both riders and coaches and cyclists spend some time manipulating their cadence in order to maximise their training effects,” says Professor Passfield.
“As scientists we are struggling to explain the underlying mechanisms for how it makes a difference. It’s all the more challenging as pedalling a bike seems a relatively straightforward task when taken at face value,” Passfield added.
A significant mystery still remains to be solved by science, he says. “Cyclists do not, in practice, choose to pedal at the cadences that scientists find to be the most economical in terms of oxygen cost. Instead they choose to pedal notably faster than this,” says Professor Passfield.
So more studies are needed to find out why cyclists prefer slightly higher cadence than current scientific knowledge says is the most energy efficient. One thing is for sure, though – no pro is going to waste any energy by pedalling quickly in a low gear.
Pedalling rate is an important determinant of human oxygen uptake during exercise on the cycle ergometer, by Federico Formenti, Alberto E. Minetti, Fabio Borrani, was published on September 14 2015 in Physiological Reports: Volume 3, Issue 7, e12500, pp.1-10.
This article was originally published in 2015