WHOOP 4.0 – Is it worth it? Does improved accuracy entice you?

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WHOOP 4.0 – should you re-join? or join for the first time?

Freebie: Free WHOOP 4.0 Band + a month free subscription HERE

Yes, really!

WHOOP 4.0 has already started shipping to some lucky customers who were quick to order their free band upgrade on the day of its announcement. Like many of you, mine is still en route somewhere from China to my house via who knows where. Good things come to those who wait.

WHOOP’s app has already been updated and those of us still on Band 3.0 can see various screens and metrics that just have blank data for us now. So, at least we have an idea of the goodness to come. But what about those of you who may have held off jumping onboard with WHOOP and are now intrigued by new claims of accuracy? Is 2021 a sensible year to go-WHOOP?

Probably. Maybe. Is the answer. Here’s why.


WHOOP 4.0 – Is it worth it?

WHOOP’s premise has always been awesome and I remain staggered that no other sports tech company has made a serious effort to compete directly with it. What is a unique product worth?

WHOOP 4.0 – A Re-Explainer

Simply put, WHOOP is an Athlete’s Physiology Tracker.

It tracks your exertions, recoveries and sleeps via a heart rate sensor and other sensors. One of its key selling points is the form factor. Ie it’s a comfortable, customisable and stylish band that can be worn 24×7 for several days. On the whole, it’s a wear-and-forget device that doesn’t have the physical intrusion of a bulky watch. As well as tracking you it also coaches you on how long to recover for, what your recovery state is, how much sleep you need and more besides. There are some pretty cool analytical reports too if that’s your thing although I love using the great app.

WHOOP is less good when you need instant numeric feedback for your sport. So, if you are a runner or cyclist who wants to know their exact performance stats during a workout you won’t get it. There’s no screen to tell you your speed, power and so on. It’s not designed to do that. That’s when you need something like a watch.

Thus, if you are a team sports player, WHOOP is a great tool, with the caveat that you will need to wear it on your upper arm in contact sports. Halfway through a game, how many footballers look at their running on a watch?…A: none.

Future View: With WHOOP’s acquisition of PUSH we can expect a market-leading WHOOP ecosystem for lifters, providing they get the accuracy right.

Accuracy Again

WHOOP’s historic mistake was to respond to customer demand to broadcast heart rate so that gym equipment could display it. Naturally, this meant that people like me (sports tech testers/reviewers) could now precisely compare its accuracy to medical-grade chest straps. Clearly, Whoop 3 is not as good as a Polar H10! But then neither are all other wrist-based optical heart rate monitors as results vary considerably between people and depending on how they use the technology. For example, here’s the latest, greatest Garmin Fenix 6 Pro, whose green heart rate line looks great….until it doesn’t. It’s wrong…the Garmin is wrong.


For my steady-state training, Whoop 3 was nearly always sufficiently accurate to give meaningful and actionable results. For some people, it’s not. Same with Garmin, Polar, Fitbit, Apple.

But, I tend not to do much gym work and that is the area where all wrist-based optical HR tech struggles.

That said, WHOOP4.0 appears to be more accurate than the 3rd Generation Whoop strap. This will likely mean that the tracks it produces during workouts will be smoother especially if you wear it on your bicep and hopefully more people will get more accurate tracks. So, if accuracy had previously put you off, it might now be a time to think again.

Here are some of my recent charts for Whoop when cycling and running with Whoop worn on the bicep. Simply put..it has good accuracy.

There were also some concerns about how Whoop assessed sleep recovery. Since August, this is now calculated in one of the two ‘correct’ ways.

Whoop 4.0 – What Else will convince me?

My bug-bear with Whoop has always been the strap’s hinge mechanism which periodically comes apart. Sure, Whoop would replace it if it broke, it’s just mildly annoying. Whoop 4.0 has a new strap mechanism and an improved charger that more snugly fits the Whoop.

Other than that it might be the new sensors that convince you. I’ve already been seeing respiratory rate for some time on the app and Whoop 4 adds SpO2 (blood oxygen) and skin temperature. Neither of those is interesting to me in themselves, probably nor to you either. However, they can both be used to improve the accuracy of sleep tracking and recovery.



The WHOOP 4.0 strap is totally changed in all key respects and alongside that, we see a new apparel range that allows WHOOP 4.0 to be worn in a variety of places on the body.

The key takeaways are innovative new tech that is hopefully accurate plus some sports clothing.

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Here are the new details

  • 33% Smaller: WHOOP 4.0 is 33% smaller than WHOOP 3.0 and claims an improved 4 to 5-day battery life
  • new Optical Heart Rate Sensor: The sensor has 5 LEDs (three green, one red, and one infrared) and 4 photodiodes. Couple that with WHOOP’s algorithms and WHOOP claims its accuracy is validated by 3rd party testing.
  • Next-Gen Battery: Earlier this year, Sila Nanotech received a huge investment to support the R&D of their new battery that uses silicon-based anodes for the first time in a Li-ion battery. This tech will probably make its way into electric vehicles but WHOOP gets to use it for the first time in their product. The key benefit is that there is a 17% space-saving or, put another way, this almost boosts 4-day battery life to 5-day battery life. Industry players Garmin, Apple and Samsung must be eying this eagerly.
  • Battery Pack 4.0: There’s a newly designed battery pack that can charge on the go as well as respond to a tap to show the charge level
  • Sleep Coach + Haptic Alerts: Gentle vibrations can wake you up at the right stage of your sleep cycle.
  • Pulse Oximeter: Supports blood oxygen calculations (SPO2) to offer new physiology insights
  • Skin Temperature Sensor: Temperature is another new metric that can be used to improve health/illness features, menstruation monitoring and sleep stage calculations.
  • Health Monitor: Track live heart rate, skin temperature, SpO2, resting heart rate (HRrest), heart rate variability (HRV), and respiratory rate in one view. Copy 30-day or 180-day trends of these metrics to your coach, trainer, PT, or physician
  • IP68 & Waterproof to 10m – hmmm. Don’t dive in!
  • BLE Support – ANT+ not supported. It’s a Bluetooth Low Energy/SMART sensor.

WHOOP 4.0 Accuracy Results – GYM Results & Wrist-Worn | FitGearHunter

WHOOP’s Any-Wear clothing range has pouches into which the WHOOP sensor easily slips and reads data from your torso, waist, or calf. The clothing collection includes sports bras, compression tops, leggings, shorts, and athletic boxers which vary in price from $54 to $109.

  • Fast Link Slider: This allows bands to be more easily removed, swapped and then for the sensor to be placed in the clothing if desired.
  • SuperKnit & HydroKnit Bands: Respectively these are for comfort/durability and a fast-drying version for sport
  • Any-Wear Detection: The clothing and WHOOP interact so that WHOOP records the wear-position.


Who Gets a Free Upgrade?

I’ve already successfully completed the upgrade request process – it works.

Existing subscribers can register for the new WHOOP 4.0 and get a free upgrade sent to them later this month.

If you are a founder member it’s different. You should find that your existing WHOOP 3.0 membership is now deactivated in the app. You will need to upgrade to the subscription service and provide valid credit card details. I guess that isn’t what you originally signed up for when you bought your original WHOOP outright but it is what it is. As a sweetener WHOOP gives you free 2-year membership until September 2023. You can upgrade online or through your app where the screen should look like this.

when is whoop shipping?
Reserve yours or subscribe: Whoop.com


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2 thoughts on “WHOOP 4.0 – Is it worth it? Does improved accuracy entice you?

  1. Whoop still suffers from the inability of the user to edit HR spikes which occur frequently and result in changes in the user’s HRmax. This artifactual HRmax results in inaccurate strain values (which are based on HRmax) and can only be edited by contacting Whoop support. HR spikes are not uncommon to optical heart rate bands and watches but many other platforms allow user editing. Another solution to optical rate errors is the ability to link chest straps to optical heart rate devices (e.g., Apple Watch, Garmin watches), vastly improving metrics.

    1. fair point, in generality
      i’ve had no hr spikes with whoop 4 when worn for exercise on the bicep. If it were worn on the wrist then…maybe
      I’m also not entirely sure that a 2 second HR spike either affects the HRmax setting or the TRIMP-like impact of the workout.

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