How Aero is too Aero?

Dropping your torso may help you slice through the air, but at some point you pay the price in power. Here’s how to find your aero sweet spot.

Bicycling |

Dropping your torso may help you slice through the air, but at some point you pay the price in power. Here’s how to find your aero sweet spot.

Photograph by James Startt
Photograph by James Startt

Aero is everything…until it’s not. On a flat road, aerodynamic drag is your biggest obstacle. You use about 80 per cent of your power output to overcome wind resistance when you’re hammering down the road. Using aerobars and dropping your torso toward your top tube shrinks your frontal surface area, making it easier to slip through the wind and go faster. But as a new study points out, there’s a point of diminishing returns, because it’s harder to take full deep breaths and to push the pedals to produce maximum power when you’re all hunched over.

To show how dramatic an impact extreme aero positions can have on power output, a team of British researchers had 19 trained cyclists perform a series of power tests, starting at a 24-degree torso angle and dropping incrementally to zero (or as close as possible; not everyone could get that low). Every performance parameter tested, including efficiency, heart rate, cadence, V02 max, and peak power output worsened as the torso angle dropped. Power output fell 14 per cent—51 watts—from the highest position to the lowest. Of course, the cyclists’ frontal area was also reduced (by up to 14 per cent) as they got lower. So the riders would be more aero in real-world conditions. However, the researchers concluded the lowest position hindered performance so much that it should be avoided even by trained competitive cyclists. For the other positions, it’s a trade-off between how many watts you lose to impaired performance versus how many you gain in aerodynamic advantage.

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“It’s pretty easy to test for yourself with a power meter,” says power-training guru Hunter Allen of Peaks Coaching Group. “But you can also test it by simply using speed and RPE [rating of perceived exertion].” Here’s what he recommends:

Establish a baseline. Find a nice flat section of road that you can ride uninterrupted. Cover up your computer so you can’t see your numbers. Then, using your normal position, do two out-and-back runs at an RPE of 6 on a 1 to 10 scale, with 10 being as hard as you can go. Check and record your average speed.

Test yourself. Lower your torso a few degrees. Again, without looking at your numbers, repeat the course at the same RPE. Check and record your average speed. Repeat the test (without wearing yourself out) in incrementally lower positions until your average speed slows down.

Stretch and train. Keep your position right at that breaking point for three weeks, riding at least three times a week, including one long ride on the weekend. During this time, stretch your hamstrings, glutes, calves, quads, and hip flexors daily.

Retest. After three weeks, go back out and retest yourself to see if you can now ride faster in that position. If yes, lower a bit more and see if you can go faster even lower. If not, bump your position back up to where you clocked your fastest average speed.

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