Does Drag Matter for Runners?

I spent an afternoon earlier this month at the Milton Velodrome in Canada, watching a cyclist from the Canadian national team do aerodynamic testing. It was pretty amazing to see the big changes that result from tiny adjustments—like a reduction of about four per cent in drag area just from shifting the seat and handlebars forward by less than an inch, as I described in my Globe column this week.

The guy overseeing the testing was Andy Froncioni. He works for Alphamantis, a company that has developed a system for calculating drag area at the velodrome rather than in a wind tunnel, based on the relationship between power and speed during a standardised 12-lap riding protocol. The idea is that, aside from no longer needing a wind tunnel for testing, you get more realistic riding conditions (e.g. the side-to-side sway of the bike).

Anyway, as the afternoon of ultra-subtle adjustments wore on, Andy kept turning to me and asking, “How is this not a bigger deal in running?” The obvious answer, of course, is that the speeds are so much slower in running that you end up spending only a tiny fraction of your energy overcoming air resistance. When you’re cycling on flat ground, you typically spend 70 to 90 per cent of your energy overcoming air resistance. In running, according to one of the classic studies, the cost is much smaller:

“The energy cost of overcoming air resistance on a calm day outdoor was calculated to be 7.8 per cent for sprinting (10 m/s), 4 per cent middle-distance (6 m/s), and 2 per cent marathon (5 m/s) running.”

Still, a few percentage points is nothing to sneeze at. At the Endurance Research Conference at the University of Kent, UK last month, Andy Jones gave a talk about the prospects for a two-hour marathon in which he argued that dramatically reducing air resistance could make an enormous and immediate difference. Simply arranging for a runner to draft behind others all the way to the finish rather than just to the halfway mark, he argued, would enable a runner to go two to three minutes faster.

So how do you minimise air resistance? Drafting behind other runners is what we usually think of. But Froncioni was also shocked at how common loose clothing and wild hair are even among elite runners. He says that he begins to see aero effects starting at about 15 km/hr, which is 4:00/km, far slower than top runners race at. And the effects would be magnified on windy days: if you can feel the wind whipping through your hair or ruffling your singlet, you’re spending energy overcoming it.

In all probability, aerodynamics may be irrelevant for most runners in most situations. Still, I’d love to see some more tests of it. When Specialized Bicycles built its own wind tunnel a few years ago and started doing oddball tests, they produced some very surprising results—suggesting, for example, that shaving your legs saves more time than upgrading from a 1980s steel bike to a modern aero bike. Maybe runners would discover some similarly surprising results.

Here are a few of the results from Specialized’s tests, which I pulled together for my Globe article, shown as time saved for a 40K time trial (note that it’s fairly independent of speed, since slower riders experience less drag but experience it for longer):

Shave your legs: 70 seconds.

Hair in braid instead of ponytail, bun, or down: 14 seconds.

Switch from casual medium jersey to form-fitting size small: 91 seconds.

Move water bottle from seat post to down tube: 25 seconds.

Water bottle in back pocket or attached behind seat: 38 seconds.

Trade your 1980s steel bike for a modern aero bike: 50 seconds.

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