Shaven legs = faster bike leg?

Article from Runner’s World on better bike results with shaven legs! Not for me thanks!

Shaven legs proven to improve performance

A closer look at the purported benefits of leg-shaving.

by Alex Hutchinson

Last month I blogged about a surprise result from wind tunnel testing, which claimed that cyclists can save on the order of 15 watts – equivalent to over a minute on a 40-km time trial – simply by shaving their legs. One of the mysteries surrounding that result was that previous testing had suggested that the aerodynamic drag associated with leg hair was negligible. If you Google “cycling leg hair” or similar searches, the first result that shows up is this Bicycling article from a few years ago, which references a classic 1987 test (also performed for Bicycling magazine) by aerodynamic engineer Chester Kyle, which concluded that for leg-shaving, “the aerodynamic improvement is roughly 0.6 percent, which could result in a savings of around 5 seconds in a 40km time trial ridden at 37kph.” Most of the other online discussion about shaving references the same result, which is why most people assume(d) that shaving was mostly about aesthetics, road rash, and/or massage.

I decided to dig a little deeper into the leg-shaving question, and the related question of scientific replication. When I asked Mark Cote, one of the aerodynamicists at Specialized who conducted the new tests, why his results differed from the previous ones, he noted that he’d asked Chester Kyle – one of his mentors – the same question. Here’s Kyle’s description of the original test:

“In 1984, we decided to test the wind resistance of various fabrics on a human figure.  Since we only had access to a small wind tunnel we used a lower leg model in the wind tunnel and put various socks on the model, and also added glued hair to the model.”

Suddenly the discrepancy doesn’t look so surprising anymore – the tests were performed under very different conditions! The newer tests, performed with live cyclists actually pedalling in a wind tunnel optimised for cycling, seem more likely to provide a reliable result (though it’ll still be interesting to see if the new results can be replicated in a different facility). On that note, Cote also had some interesting things to say about the challenges of testing with live cyclists:

“In previous years, I personally questioned the precision and repeatability of testing with humans on the bike.  This was when we would do 1 day of athlete testing in a 3 day block at tunnels we were renting.  Now that we’re testing athletes multiple days per week, we’ve been able to verify that athletes who know their positions well can repeat as well as a static mannequin.  Noticing this through repeated athlete testing has changed how we test now – we use live riders now for most tests when we used to use mannequins in the past.”