Science Interviews

Interview

Tue, 8th Jul 2014

How much energy do cyclists use?

Dan Gordon, Anglia Ruskin University

Listen Now    Download as mp3 from the show Saddle Up: The Science of Cycling

The world’s biggest cycling event, the Tour de France has just visited Britain.

To celebrate, we thought we’d take a peep behind the yellow jersey to find out the science behind the Tour de France; so Kate Lamble and Chris Smith headed Sports labdown to Anglia Ruskin University, to the Lab of Sports Scientist and former Paralympic cyclist Dan Gordon so he could push them to their limits.

Dan - I was a track cyclist so I used to do kilometre time trials and sprint cycling on the velodrome.

Chris - Any medals?

Dan - I've got a few, yeah. I was European champion, I was a world champion, and I still hold a world record.

Chris - So, tell us about the laboratory we’re in and the work you do here at Anglia.

Dan - Yeah. This is one of our exercise physiology laboratories and we’re equipped here for assessing everything from cardiovascular, cardiorespiratory function through to what's happening in the blood and what's happening in the muscles.

Chris - You've agreed to do some experiments for us today. You're not going to do the cycling, but we’re going to make Kate do some of the cycling and you've also brought along a volunteer. Who are you?

Karin - I'm Karin and I'm a sport scientist student here at Anglia.

Chris - And also a keen cyclist.

Karin - A keen cyclist, a keen runner, and a keen spinner.

Chris - So Dan, what are you going to do with our two victims?

Dan - Okay. What we thought we’d do is we would get these guys to experience what it’s like to cycle in the Tour de France. There's a lot of data now that's been collected over tours in terms of what the amount of work that these cyclists are doing and we measure the work on the bike through the crank that is the bit where the pedal is connected.

We know that in the males who are competing Tour de France, they work at about 7 watts per kg. So, it would be a bit unfair to make both Kate and Karin work at the same workload as somebody like Bradley Wiggins. So, we’ve looked at what's called the Tour Feminin. So, this is the female version of the Tour de France. In the female version, they're averaging about 3.3 watts per kg. So, this means that in this demonstration, Kate is going to cycle at 135 watts and Karin is going to cycle 175 watts.

Chris - So, this is based on their body weight.

Dan - It’s based on their body weight and they're going to maintain the cadence, that is the rate at which the pedals go round. And so, we know that the average cadence across the 21 days is 70 revs per minute. So, we’re going to get them to try and maintain that and then we’re going to look at partly how long they can go for and also, we’re going to try and record some heart rates to get a picture of what the cardiovascular response is.

Chris - And just to be clear, when you say 70 revs a minute, what does that translate into in terms of speed over the ground for the cyclist?

Dan - If we take the 21 days as a whole, it does depend upon the year of the tour. It does depend upon how many mountain climbs they've got, but it ranges anywhere between 42 to 44 km an hour.

Chris - You up to it, Kate?

Kate - I'm beginning to regret this entire endeavour if I'm perfectly honest.

Chris - Do you want to come and set them up Dan? Talk us through how we’re going to do this.

Dan - Karin is already on her cycle ergometer. So, she’s adjusted it to her body position and Kate is going to now jump on and what we’re going to ask them to do, is if you guys just want to gently start turning the pedals. This is Kate’s wattage about to go on. So, we’re going up from 50, to 90.

Chris - So, this is an electronic selector. We can see the scale going up. Wow, it’s quite 128, 130.

Dan - So, we’re at 135.

Chris - That's quite a heavy load you've got on there.

Kate - Yes. I don't know why Dan decided to make it so hard for me, but I'm currently managing it. I'm on about 80 revs a minute. How fast is that compared to the Tour Feminin, Dan?

Dan - You're averaging a little bit faster. They're averaging about 70 revs per minute. But if you're comfortable at 80, I would say, stick at 80. So, what we’ll do is we’re going to measure Kate’s heart rate while she’s doing this. Okay, so if you want to give me your finger. I'm just going to put this little Doppler on the finger. So, Kate is currently working a heart rate of about 150 beats per minute.

Kate - That's really unfit. Is that unfit?

Chris - That's quite high, isn’t it?

Dan - That's relatively high, but bear in mind that Kate has only just started. So, the heart rate will accelerate quite quickly initially. We would expect riding on a flat stage. The heart rate can be anywhere between 119 and 130 beats per minute for about 6 to 7 hours.

Chris - So, let’s see how Karin is getting on. Are you feeling alright?

Karin - Yeah, it’s a little bit tough, but I'm still alive.

Chris - Let’s have a look at Karin’s heart rate. A much fitter, 132.

Dan - So, there you go. So, you've got this comparison. So, Karen who does a lot of aerobic exercise, cardiovascularly, she’ll be strong and she’ll have a slightly bigger heart. She’ll be able to use the blood and the oxygen that's in that blood more efficiently at the muscle. As a result, she’s using less energy for every time she pushes down on the pedal.

Chris - How long are we going to subject them to this?

Dan - As long as they can go for I think.

Kate - I'm beginning to feel like this is just an exercise embarrassing me, this entire show. 

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