What was the strange black arm sensor worn by Tadej Pogačar at Strade Bianche?

To celebrate his record-breaking fourth win at Strade Bianche, Tadej Pogačar climbed off his bike at the faux-monument's finish line in the Piazza del Campo, raised his arm aloft and punched the air.

In doing so, through the white fabric of his rainbow-bands skinsuit, a black sensor could be seen on the underside of his upper arm, but what was it?

Naturally, internet forums lit up with rumours. Perhaps it was a new core temperature sensor, or an optical heart rate monitor, or even something more advanced like a real-time blood lactate monitor to help the Slovenian measure his effort to perfection.

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Many minds were even cast back to the 2023 edition of the same race, when American Kristen Faulkner was disqualified for wearing a Supersapiens continuous glucose monitor.

But it turns out that the truth is somewhat less novel. According to the team, it was merely Pogačar's Whoop sensor.

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Though unconfirmed, it's most likely the brand's latest 5.0 sensor, which tracks heart rate, heart rate variability, sleep, and a host of other metrics to quantify strain and recovery for athletes.

Typically worn on the wrist via an elasticated strap, and perhaps most visibly on the wrist of Mathieu van der Poel, Whoop's sensors can be worn elsewhere on the body too.

The brand makes its own line of activewear with sensor-sized pockets that the Whoop sensor can be slotted into to hold it against the skin. Assos even makes a pair of bib shorts with the same pocket on the rear.

Given the position of Pogačar's sensor, we suspect had shifted throughout the race, and it appears he simply relied on the skintight nature of his Pissei-branded skinsuit's sleeves to hold it in situ, rather than a pocket.

Pogačar has been seen sporting the Whoop strap on social media since the start of the year. Before this point, the UAE Team Emirates XRG squad was sponsored by one of Whoop's competitors, UltraHuman, whose sensors were placed in a ring, similar to the other big player in the space, Oura.

Exactly why the Slovenian chose to wear the Whoop sensor on his upper arm, though, is unknown.

The massive Richard Mille watch on his other wrist suggests aerodynamics wasn't the concern, and also that he hadn't been put off wearing wrist-attire by last year's incident, when the watch cut into his wrist over the bumpy cobbled sectors of Paris-Roubaix.

Regardless of why, the next thing we want to see is the data from the ride. Whoop has been kind enough to upload this Instagram post showing that his max heart rate was 198bpm, but that's about as detailed as it gets. His Strava upload is unfortunately devoid of any heart rate and power data, so we're left pondering the numbers it takes to ride for over 200km – almost five hours worth – at 42.2km/h (26.2mph).

Notably, Pogačar's not the only rider we've noticed with tricks up his sleeve, though. Per Strand Hagenes' late solo attempt at the recent Le Samyn gave the Visma-Lease a Bike man some time in the limelight, and up the sleeve of his left arm, we spotted a protrusion of sorts.

Upon asking the team for an explanation, Cyclingnews was told it was "just some empty gel wrappers." At first, we thought he was wearing a long-sleeve jersey, which would make this explanation highly improbable, but we've recently seen a photo of the gel-wrapper-stowing in action, proving that it's actually a short-sleeve and perfectly-matched pair of aero arm warmers.