Whoop 5.0 vs 4.0 Underwear for BJJ: Why I’m Sticking to Old Gear

The Whoop 4.0 underwear was, quite simply, the best wearable placement I have ever used for jiu-jitsu. It was the solution to a decade-long problem of how to track heart rate and recovery during high-intensity grappling without the device getting in the way or causing an injury. However, the Whoop 5.0 redesign has fundamentally changed that experience. By moving the puck to what I consider the worst possible spot for a grappler, the device now falls off mid-roll, digs into the body on impact, and tracks significantly worse than its predecessor.

I currently own six pairs of the legacy 4.0 underwear and exactly one pair of the 5.0s. That ratio tells you everything you need to know about my recommendation. If you are a grappler, the 4.0 design remains the superior choice, while the 5.0 is a last-ditch option that requires DIY modifications to be functional. I recently shared these thoughts in a survey Whoop sent out regarding their garments, but I wanted to put the full argument here for anyone currently deciding whether to upgrade their kit.

Quick comparison: Whoop 4.0 vs 5.0 underwear for grappling

Why the 4.0 placement was perfect for BJJ

When you put on the Whoop 4.0 underwear, the puck sits snugly at the back of your hip. That position is a "neutral zone" in a way that matters immensely on the mat. When you take a fall or get swept in jiu-jitsu, you usually land at an angle. The 4.0 hip pocket takes that impact flat against the muscular part of the hip. It is not located in the small of the back where it would strike the spine or kidneys, and it isn't positioned on the front where it would interfere with your guard or waistline. It is just there, doing its job silently.

I bought six pairs of these specifically so I could train every single day and only have to run a laundry cycle once a week. They have been through hundreds of wash cycles—to the point where the white branding on the back has completely worn off—yet the elastic and the pocket integrity have held up. These are my favorite garments Whoop has ever produced, and they set a high bar that the new generation simply hasn't met.

The 5.0 puck placement problem

The Whoop 5.0 underwear moved the sensor from the back of the hip down to the side of the butt. While this might look like a minor adjustment on a mannequin, on the mat it is a disaster. The side-of-the-butt area is a primary impact zone. Whether you are playing seated guard, getting taken down, or simply transitioning through side control, that specific area is constantly under pressure.

Because the puck now sits on a high-pressure point, it digs into the flesh during hard landings. More importantly, the mechanical stress of grappling causes the puck to pop out of the pocket. I lost my 5.0 puck twice in the first year of owning just a single pair. Because you have to remove the puck to wash the garment, it often ends up sitting on a counter, and eventually, it "walks away." The design seems to assume users will own many pairs and always have a puck installed, but the design itself is exactly why I refused to buy more than one.

The 5.0 also tracks worse for me

Beyond the physical comfort and retention issues, the 5.0 underwear does not seem to maintain the same level of skin contact. I can see the discrepancy in the data. On training sessions that I know were high-intensity grinds, the 5.0 often returns data that looks far more "muted" than it should. My hypothesis is that the new placement requires a specific body type—likely a smaller waist and a larger gluteal area—to maintain the necessary tension. For my build, the puck simply doesn't stay flush against the skin, leading to dropped heart rate samples during the most critical parts of a roll.

The spacer trick that keeps the 4.0 gear working

The real kicker is that the Whoop 5.0 puck is not the same size as the 4.0. The 5.0 is slightly larger in terms of its height (elevation off the body). This means the legacy 4.0 underwear pockets do not natively hold the 5.0 puck with enough security; the 5.0 puck is prone to sliding out because it stretches the pocket differently.

I found a fix that is as dumb as it is effective. I take a small strip of jiu-jitsu gi finger tape, fold it over itself several times to create a firm spacer, and slide it into the 4.0 underwear pocket before inserting the 5.0 puck. This creates enough internal tension to lock the puck into the legacy 4.0 position. It takes ten seconds to do, and it solves the problem entirely. The fact that I am essentially hacking $30 underwear with athletic tape instead of purchasing the "upgraded" version illustrates how poorly Whoop misjudged the needs of the grappling community.

Why bicep and chest straps fail for my style

Most of my teammates use the bicep strap, but I have never been able to make it work. The strap tends to pinch as you slide it on, and the moment I flex my arm, the puck shifts. If a teammate gets a strong grip on that arm during a scramble, the puck often goes flying. I have actually had to stop a match to throw a loose strap off the mat. That is a level of distraction I cannot afford when I'm rolling against purple belts and up.

Chest straps are another popular alternative, but they are highly dependent on your game. I play a lot of triangle and semi-open guard, which involves pushing my opponent's arms into the center of my chest to create angles. A chest strap gets hit on almost every grip and transition. Furthermore, I prefer a "set it and forget it" approach. If the Whoop registers the session as a workout, great. If it doesn't, I don't go back and manually edit it. I want the wearable to be invisible, and only the 4.0 underwear has ever achieved that.

Should you buy a Whoop right now?

While I am still using my Whoop, I don't think it's a mandatory buy for most people today. The garment issues alone are a hurdle, and the competition has finally caught up. My wife uses an Amazfit and finds it excellent for her needs. Fitbit recently released a device with a bicep-friendly form factor that is significantly cheaper. Garmin is also rumored to be launching a screen-less competitor later this year. For a grappler who just wants simple, reliable data without a high monthly subscription, brands like Fitbit or Amazfit are becoming more practical choices.

Wearable accuracy and the role of AI

Despite the garment issues, I still value the data when I can get it. There is a common claim online that wrist-based heart rate is 30-50% inaccurate. In my experience, that 30% figure is a rare upper bound that only occurs during maximum intensity sprints. For the steady-state cardio and general aerobic load of a BJJ class, my Whoop and my Garmin (worn on the other wrist) usually read within a few beats of each other. Consistency is more important than absolute laboratory precision; you need to know if you are working harder today than you were last Tuesday.

The real value in my current stack comes from how that data is processed. After a winter where I caught the flu three times, I stopped trying to manage my own intensity and handed my schedule over to Aria. Both Garmin and Whoop tend to be too aggressive after an illness, encouraging you to ramp back up to 100% the moment your fever breaks. Aria blends the recovery scores from Whoop, the training load from Garmin, and my lifting output into a single, cohesive plan. It knows when to tell me to back off, even when the individual apps are screaming for more "strain."

Ultimately, if Whoop reverts the garment design and makes the puck placement compatible with the "neutral zone" of the hip again, I will be the first person to buy a dozen pairs. Until then, I’ll be over here with my old 4.0 gear and my tape-spacer trick, waiting for the hardware to catch back up to the needs of the mat.

Watch the full breakdown on YouTube: Whoop 5.0 Garments Failed Grapplers.