'Maybe she's found something in the wind tunnel' - Aerodynamicist Dan Bigham’s take on Billie Eilish’s Glastonbury leg tape

The thing about us cyclists is sometimes we just see things differently. So it was as I watched Billie Eilish’s headline set from Glastonbury on Friday night.

When the sultry pop singer strode onstage in Lycra shorts sporting a complex arrangement of k-tape on her shins it was impossible not to wonder, just how aero would her legs be?

You see, at the last Olympics the Danish men’s team pursuit squad unveiled just such a trick, controversially wearing the supportive tape up the front of their shins in the search for aerodynamic advantage. It was, of course, swiftly banned by cycling’s governing body and resident spoil sport the UCI. 

One of the architects of that was Dan Bigham, the British time-trialist and aerodynamicist who is currently Ineos Grenadiers performance engineer, who was working with the Danish squad at the time.

I wondered what he would make of seven-time Grammy winner Eilish’s set-up? “I think Billie needs to spend a little bit more time optimising tape location and tape size. But she's on the right track to some significant performance improvements,” says Bigham with a chuckle at the daftness of the question.

It was impossible to judge if he was right as Eilish bounced around the main stage of the world’s biggest music festival while the sub-bass of her 19.5 million selling single Bad Guy rumbled out of the speakers.

The principle in putting tape on your shins for aero gains is Bigham explains “an opportunity to create a turbulent boundary layer to resist separation in an adverse and pressured gradient”. Or to put it more simply the turbulent air it creates stays close to the leg for longer, which helps the leg travel through the air.

Generally, you want to have the k-tape on the leading surface, in this instance the shins, in a “big wide strip” explains Bigham. “But she's quite ad hoc [with the placement]. I wonder if there's something else at play, maybe she's found something in the wind tunnel,” suggests Bigham wryly.

“Where Billie has it is heading into the realms of dangerous trip location. The further rearward you place it, the more benefit you can get up to a point where you no longer get any benefit, it's kind of a cliff edge.”

Turning serious for a second, hour record rider and nine time Cycling Time Trials national champion, Bigham adds that the benefits of tape on the legs haven’t been fully explored. “Genuinely, there probably is more optimization to be done in that area. But I feel like the UCI would not be too happy if I turned up with some more knee injuries,” he says.

Eilish has reportedly spoken about suffering with shin splints while performing in the past, which is likely the reason she is wearing the tape. 

Bigham picks up on the fact that she has some “nice aero” arm skins that would help her TT times before adding: “You’re losing any other gains with how baggy that top is.”

So how’d you rate the whole ensemble, I ask Bigham? “Seven out of ten,” he concludes.