HRbutt // WHOOP+Tyr: Butt-measured HR on TYR Swimwear

TYR X WHOOP Durafast Elite® Jammer Swimsuit
I took the gold band off during use

TYR x WHOOP Durafast Elite Jammer Swimsuit

This is perhaps the world’s first smart jammer swimsuit but I was more interested in measuring HR on my butt :-). It was one of those kinds of days.

Must Read: Is WHOOP Accurate? Detailed WHOOP 4 Review

TYR x WHOOP – Background

WHOOP apparel includes lifestyle and functional clothing that has a special pocket to slip your WHOOP into and still record HR. It’s generally pricey but pretty good quality stuff and I would definitely recommend to anyone owning WHOOP that they buy one of the bicep bands. That’s the best way to ensure you will get accuracy during land-based sports with your WHOOP.

Just before Christmas WHOOP announced a partnership with TYR for swimwear. I got some pairs of the jammers at the time and have taken a while to get around to this write-up.

What is the Jammer Windsuit?

TL;DR – standard TYR trunks with a little pocket for WHOOP on your butt.

But WHOOP might phrase it a bit better. Something along these lines…

The suit combines TYR’s performance-focused fit and materials with WHOOP Any-Wear technology, allowing you to move your WHOOP 4.0 device from your wrist to your swimsuit for maximum workout tracking. Rigorously tested for comfort and data accuracy, these suits are designed to help you improve your performance and reduce drag in the water. The WHOOP Body line of technical garments is engineered for multi-point wearability and has built-in WHOOP pods to detect data across your body. WHOOP 4.0 leverages Any-Wear technology for optimal sensor placement, and is only compatible with WHOOP 4.0 device.

It comes in an all-black colour as well as a greyscale colour with a camouflage pattern – that’s what I got.

You say, “Hey, we wanna hear about your butt”

I followed the WHOOP butt sizing guide carefully and then erred on the small side as I wanted something tight to minimise drag. The fit is really tight on my cycling quads but do-able! There is a good seal around the quads and a drawstring for the waist that wasn’t quite able to remove a small air pocket over my spine. You’ll be pleased to know that it fitted my butt perfectly.


Product Details

  • 94% Polyester / 6% Spandex
  • Premium fabric that is 100% chlorine proof, 100% colourfast and able to sustain 300+ hours of performance
  • 2-layered, fully lined swimsuit with anti-microbial properties
  • Hand wash in cold water after each use with mild soap, no detergent or bleach. Hang dry away from heat, do not iron or wring.

HR Swim Tests


I conducted a test using a Garmin 955 Solar oHR and an Apple Watch 6 (oHR) to track my heart rate during a 30-minute swim. The set consisted of front crawl and different equipment like paddles and a pull buoy. I usually use WHOOP and broadcast the heart rate data to a Coros Pace 2 watch, but that is not possible underwater and there is no way to export WHOOP data from the app.

The results of the test were inconclusive.



The Apple Watch track had gaps in it, and while the Garmin and WHOOP plots looked plausible, upon closer inspection, WHOOP’s peaks declined towards the end of the workout, suggesting inaccuracies. The 142bpm max on the first peak was higher than expected, but the Garmin had it at 145bpm, so WHOOP may have been accurate. However, since I used paddles and the oHR is susceptible to wrist movement and water interference, the results are not entirely reliable. I cannot recommend using an oHR on the butt for swimming workouts based on this one test. Further testing would likely be limited by the inability to correctly export the data for a detailed analysis, so I don’t plan further tests.

It is worth noting that I also casually looked at my heart rate during runs to and from the pool when using the same jammer/trunks, and while the results appeared plausible, they were likely also inaccurate. It is best to use a biceps strap with WHOOP for accurate results during land-based workouts, and wear it on your wrist for tracking at rest and during sleep.

Take Out: Butt-generated HR data while swimming with the WHOOP looks usable from a cursory visual inspection but I certainly can’t say it’s accurate.


Take Out

Both men’s and women’s versions are nice-to-haves for committed WHOOP users. TYR sells the swimwear as meeting a performance standard and I have no reason to doubt the voracity of that claim.

If you are using paddles then it’s quite likely that HR measured on the wrist will be more inaccurate than normal. But if you’re just swimming regularly, and quickly, then placing WHOOP in your Jammers will reduce a bit of drag.

Perhaps the biggest surprise to me was the realisation that a butt-worn WHOOP means that when you’ve finished and got changed, your regular strap is nice and dry!


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