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At the recent Commonwealth Games, I was struck by how many runners with long hair had tied it in a ponytail. When fractions of a second can decide a race, surely looser hair is a drag?

Stephen Johnson
Eugene, Oregon, US

How much does long hair increase wind resistance or drag in running competitions? All components of the human body contribute to the drag produced when a runner tries to move through a fluid, in this case air.

Air has inertia and to make it move out of the way, you have to transfer energy from the runner to the air. As to how much extra energy the long hair demands, there was considerable analysis of this after Greg LeMond beat Laurent Fignon in the final stage of the Tour de France cycle race in 1989. For this, LeMond rode a more aerodynamic bike and wore an aerodynamic helmet, while Fignon used a standard bike and let his ponytail trail in the wind.

Calculations showed that the ponytail added slightly more than 8 seconds to Fignon’s time and that without it, he would have won.

Drag forces are proportional to the square of velocity. The speed of cycling is faster than running and in the case of LeMond, he averaged 2.8 times the speed of the recent world record for women’s 400 metre hurdles.

This would mean that the drag was almost eight times higher than in such running. So, if Fignon lost 8 seconds because of the ponytail, a hurdler would have only lost about 1 second over the same distance of 24.5 kilometres.

Scale this to a 400-metre race and the loss would be 0.0163 seconds. Is this enough to lose a race? Especially as other differences in body shape and technique probably have a much bigger effect.

A swim cap would solve the ponytail issue, and athletics has experimented with full body running suits with hoods. In swimming, the resistance of water is 784 times that of air and no serious competitor would swim with an uncovered ponytail.

Simon Dales
Oxford, UK

The power required to overcome drag increases in proportion to the cube of the speed. This means that runners go too slowly to be much troubled by drag due to their aerodynamics. Cyclists habitually go faster, so have to be much more careful with their hair.

show that, at racing speeds, a cyclist can lose 10 to 20 watts of power with a flapping ponytail. The turbulence behind their heads and shoulders grabs the hair and swirls it around. This is a big loss.

So, for cyclists, it is best to either cut their hair short so that it gets hidden by their aero-hat or have a single, tight plait. On the other hand, cyclist Peter Sagan’s hair is famously bouffant and he wins sprints/stages, but I suspect that his helmet holds his mop in tight.

Runners are largely upright and don’t present a particularly aerodynamic shape anyway, so the drag from hairstyle is probably insignificant for them.

Ron Whelan
via Facebook

My running days are over, but perhaps, like me, the reason for tying hair back is simply to keep it out of your face and nothing to do with speed or resistance.

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