Why the Tour de France champions dance with their bikes

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Why the Tour de France champions dance with their bikes


Image: Mark Cavendish at the Tour de France in 2012. Credit: Creative Commons
On July 9, as Mark Cavendish, aka the Manx Missile, approached the final of the 13th stage of the Tour de France straight away, the British cyclist stood up from his saddle and made his way through the peloton. and began vigorously rocking his bike side to side, tying the record for the most stages ever won (34).

The graceful swinging motion, known in French as “en danseuse”, to dance on the pedals, is common among elite cyclists and weekend warriors attacking the hills or sprinting towards the finish.

Whether this actually improves performance, or could even hinder it, has been a matter of debate.

A new study from CU Boulder published online this month in the Biomechanics Journal found the tactic to work.

“We found that, on average, the peak power output was 5% higher when our subjects tilted the bike as they wanted to than when they tried to minimize the tilt,” said lead author Ross Wilkinson, researcher postdoctoral in the Department of Integrative Physiology.

In a sport where a top spot can be won by the width of a tire and where cyclists are constantly looking for marginal gains, a 5% gain in horsepower is a big deal.

“In a race like the Tour, the runners will spend the vast majority of their time sitting. But in the last few hundred meters of a step, getting up and rocking the bike can give you a little extra power, ”said lead author Rodger Kram, professor emeritus of integrative physiology and director of the Locomotion Laboratory at CU Boulder. “It’s a small but crucial part of the bike race. “

Wilkinson envisioned the study while watching a previous Tour de France at his home in Australia. He noticed that some riders, like Cavendish, attacked hills and ended up sprinting with the bike swaying at sharp angles. Others, like Australian cyclist Caleb Ewan, seemed to deliberately minimize the lean when sprinting out of the saddle.

Some trainers and experts have argued that swinging the bike wastes energy and warps the tires, increasing resistance and decreasing performance. “Cyclists should reduce swaying bikes,” a 2018 study proclaimed.

But many trainers recommend it and cyclists often say it comes naturally.

For the study, Kram and Wilkinson set up a stationary bike in the lab so it could lean side to side or be locked in place. They brought in 19 recreational cyclists for a series of nine 5-second all-round sprints. For three of the subjects, they could tilt the bike as much as they wanted; for three, the bike was locked and could not lean at all; and for the remaining three riders, they were asked to minimize the incline.

When the researchers measured the maximum power output, they found that there was no difference between the locked position (which realistically could not be achieved on a bicycle moving across the ground to the outside) and the option of swinging as you like.

When cyclists deliberately tried to prevent swaying, their power decreased by an average of 5%.

“Swaying the bike doesn’t necessarily improve the horsepower you are able to produce,” Kram said. “It just gives you the same peak power on the ground that you could get in a spinning class. “

Meanwhile, battling the influence – as cyclists are often forced to do in a tight race – slows you down, the study suggests.

Researchers suspect that the swing allows the upper body to contribute more power, with experienced cyclists transferring it from their arms to the pedal as they “dance.” They also suspect that elites like those in the Tour receive an even bigger boost than the 5% encountered by mere mortals in the lab.

A 5% increase in power doesn’t necessarily translate into a 5% increase in speed, they note, due to air resistance. But the sway could reduce critical seconds when they matter most.

As well as giving fans another thing to watch out for in the final days of the Tour, as Cavendish seeks to break the record for the most stages ever won, they say the research could provide information to bike designers. Should high-end bikes be made with this rocker advantage in mind?

For recreational cyclists who train on stationary bikes indoors in winter, researchers recommend practicing “dancer” if the bike allows you to swing it at an angle.

And when you approach hills or get closer to a finish: don’t fight the bike. Dance away.

“It’s very rhythmic, like your arms, legs and the bike are all in sync,” Wilkinson said. “When people like Mark Cavendish are right, it’s really beautiful to watch. ”

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