I hope the new Whoop 4.0 fitness tracker fixes its predecessor's biggest flaw so it can take on Garmin and Fitbit in earnest

New Whoop 4.0 upgrades its sensor configuration – let's hope it will be accurate enough to challenge Garmin and Fitbit

Muscular person sitting on a weight bench wearing the new Whoop 4.0 fitness tracker
(Image credit: Whoop)

Unlike most "big" wearable companies such as Garmin or Fitbit, Whoop's smart band – a fitness tracker with no display – is not the main attraction: the real deal is its subscription-based service that provides a ton of data to help people train and recover better. However, previous iterations of the Whoop band were notorious for being inaccurate, something the Whoop 4.0 promises to amend.

Should the Whoop 4.0 have a decent heart rate sensor, Whoop will be in a good position to challenge both Fitbit and Garmin, mainly because getting a Whoop 4.0 is much less of an initial investment than buying a Fitbit Sense and especially the Garmin Enduro. As a matter of fact, the all-new device is free when you sign up for a Whoop 4.0 membership. Not bad!

As for accuracy, the Whoop 4.0 introduces an upgraded sensor configuration that now features three green, one red and one infrared LEDs (five in total), four photodiodes, and advanced algorithms to "provide even more accurate heart rate measurements", as the company states.

This setup reminds me of Polar's Precision Prime sensor, renowned for being accurate, and this fills me with hope that the Whoop 4.0 will be somewhat more error-free than its predecessors. Best fitness tracker from Whoop incoming?

Whoop 4.0: price and release date

The Whoop 4.0 is available to buy from 8 September 2021. 

Whoop Body featuring Any-Wear Technology is available in two collections with prices ranging from $54/£54 to $109/£94.

Visit Whoop and get a Whoop membership that includes Whoop 4.0 for free with access to the app for as low as $18/£18 per month.

Two Whoop 4.0 fitness trackers interlocked in front of a grey background

(Image credit: Whoop)

Whoop 4.0: an all-encompassing fitness offering

The updates don't stop with the upgraded sensor. The Whoop 4.0 is 33% lighter than the Whoop 3.0 and has five-day battery life. The (comparatively) excellent battery life is achieved thanks to Sila's silicon anode battery materials.

According to the company, the Whoop 4.0 band is the first product in the world to be powered by this tech. The new battery is said to deliver a 17% higher energy density than Whoop 3.0.

The Whoop Battery Pack 4.0 has also been updated, and, thankfully, it's now waterproof, so you can top up your Whoop 4.0 whenever you want to, even while swimming. The Battery Pack can be slid onto the band, meaning you never have to take the Whoop 4.0 off.

Whoop Body: smarter workout gear

Should you want to free up your wrist without interrupting the flow of data from the Whoop 4.0, rest assured, you can do that too. All you have to do is wear one of the new Whoop Body garments that includes compression tops, shorts, sports bras and even boxers.

In addition to apparel, Whoop has developed new accessories and designs, including the Fast Link Slider, making it easier to swap WHOOP 4.0 between various bands and Whoop Body sensor apparel.

The SuperKnit and HydroKnit Bands are also new, the former which comes pre-threaded for "ultimate comfort and durability", as Whoop puts it. The HydroKnit band is fast drying and said to be optimised for water sports and activities.

Person looking at the Whoop App wearing a Whoop 4.0 tracker

(Image credit: Whoop)

Whoop 4.0: more features, more sensors

Whoop included a range of new sensors and features with the Whoop 4.0, ones any self-respecting company must include in a new fitness wearable in 2021.

For instance, the Whoop 4.0 now has a vibration motor, so it can send haptic alerts to wake you up through "gentle vibrations" at the optimal time based on your sleep needs and cycles. It's a feature you'll find in many fitness trackers, including the Fitbit Versa 3 and the Huawei Band 6.

A bit more sporty is the Pulse Oximeter sensor that calculates blood oxygen levels (SPO2). This is one of the hottest features in running watches, and it can help you better understand how well you are acclimatised to different altitudes.

SpO2 is also often used during sleep tracking. If you ask me, it's completely useless data, unless you're a top athlete but never mind. There is also a new skin temperature sensor. Sure!

To bring it all together, Whoop also introduced a new feature called Health Monitor, with which you can track live heart rate, skin temperature, blood oxygen saturation, resting heart rate, heart rate variability, and respiratory rate in one view.

The Health Monitor also allows you to download and export 30-day or 180-day trends of these metrics into a report that can be shared with a coach, trainer, PT, or physician. To reference one more wearable at the end, the Withings Scanwatch has a similar expert feature. For reference.

Matt Kollat
Section Editor | Active

Matt Kollat is a journalist and content creator who works for T3.com and its magazine counterpart as an Active Editor. His areas of expertise include wearables, drones, fitness equipment, nutrition and outdoor gear. He joined T3 in 2019. His byline appears in several publications, including Techradar and Fit&Well, and more. Matt also collaborated with other content creators (e.g. Garage Gym Reviews) and judged many awards, such as the European Specialist Sports Nutrition Alliance's ESSNawards. When he isn't working out, running or cycling, you'll find him roaming the countryside and trying out new podcasting and content creation equipment.