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Whoop Band 4.0 Review, Is it worth it? ​💪 ​Best Discount Code & Free Strap Subscription Starter

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Whoop 4.0 Strap Review, Is it worth it?

Let’s start off this Whoop Band 4.0 review with a summary. For those of you with more time, grab a latte and enjoy the detailed heart rate tests, readiness accuracy tests, and links to CrossFit-specific accuracy results that follow further below. If you’ve just come here for the Whoop discount code that gets you a free Whoop (yep, free) and trial membership then look no further than this link (here, promotion automatically applied).

Best Whoop 4 discount code right now: Free Whoop and a free start on the app

I produced the first, detailed review of Whoop 1.0 back in Jan 2017 and have used every version since. It’s a great platform for certain kinds of athletes yet its longstanding problem for me as a triathlete was always the accuracy of heart rate during workouts. That’s fixed now, with caveats.

The Whoop 4.0 band performs better than or on a par with comparable optical heart-rate products from Garmin, Fitbit, Oura and others. What is not comparable is the Whoop recovery platform which is second-to-none. The platform’s awesomeness comes at a price though, if you can afford it that’s great, if not try this discount and try the product for 6 months.

Beware. Every single competitor product when worn on the wrist for Crossfit is inaccurate to some degree…Apple, Garmin…all of them. On the wrist, Whoop is no different. Most competitors, including all watches from Garmin & Fitbit, are also inaccurate to some degree for most people when running & cycling #IncludingMe. If other reviewers & ambassadors tell you Whoop 4.0 is (in)accurate then, simply put, it’s probably as (in)accurate as that other watch brand that you are currently considering instead of Whoop!

Whoop 4.0 review
  • Price - 80%
  • Apparent Accuracy - 95%
  • Build Quality & Design - 90%
  • Features, Including App - 95%
  • Openness & Compatability - 70%


Whoop always excelled at guiding athletes on how and when to sleep, rest and on their training intensity.

Whoop was the first, dedicated wearable for readiness metrics. 4 years later the Whoop Band 4.0 is still clearly ahead of its competitors.

The latest incarnation resolves important accuracy issues as well as boosts the quality of the strap design. Charging time and battery longevity are also notably improved with some market-leading battery tech. There is new sensor data and some designer sportswear that have special pouches for Whoop to record from.

It’s the same-old app. But it’s a great app. A few tweaks here and there accommodate the recent additions of TEMP, SpO2 and RESPiration metrics. The beauty of the app comes from the clarity given by the separation and flow between daily insights, trends and then the feedback from the coaching.

WHOOP automatically records every bodily action. Alongside that, you can add workout recording on the app, join communities as well as record in-workout videos showing your exertion.

Want to broadcast your heart rate to gym equipment or other devices? You got it…


  • Superb app with clear advice and presentation of actionable guidance for sleep, recovery and strain
  • Arm sleeve gives great accuracy even in sports
  • When worn on the wrist, resting/sleep HR accuracy is perfectly fine.
  • Comfy to wear
  • Safe to wear during most team sports with Whoop apparel like the arm sleeve


  • Few links to other data sources or platforms, although an API is planned
  • The subscription model has its benefits but…$
  • Strain doesn’t properly account for pure strength workouts. Whoop has acquired a company (PUSH) so that they can rectify this to raise the uniqueness of their already market-leading position

What is the Whoop armband?

Whoop 4 is a readiness tracker and coach that is powered by novel interpretations of aspects of your heart rate (HRV) and other physiological metrics. It uses real sports science that I would class as trusted sports tech.

How the science works

The insights into readiness and the data that support the sleep coach come from your nightly HRV, tweaked by HR and other data.

Your workout strain comes from heart rate x duration. The higher the heart rate, the more weight is given to the time spent at that level.

Recovery comes from complex maths. Signals in your heart rate at night determine how the nervous systems in your body are balanced. An average of those signals gives a nightly score that is weighted alongside your resting heart rate, sleep performance and respiratory rate. To an extent, these are all different measures of the same thing but looked at from different physiological perspectives.

A simple, single readiness number comes from this.

As you rest during the day, the more your readiness improves.

Over time, Whoop analyses how your body performs and is able to suggest the volume of sleep you need tonight to achieve a certain level of readiness tomorrow.

It’s all quite complicated but that’s the gist of it.

Whoop Strap 4 Review – Who’s it for?

If you are a gym rat, biohacker or cross fitter, Whoop could be for you. Let me elaborate

It’s smaller (Whoop 4.0 on the right)

Whoop 4 – What’s New?

The new Whoop looks similar to the Gen 1, 2 & 3 products but it’s smaller and wholly different inside. So that means it’s completely changed 😉

New Format

New Sensors

This is the core of the product and is completely new

New Battery

There are several additions to the Whoop app, the online platform and the reports the app produces. Partly this covers the new pieces of data that are now captured but the Whoop platform is a continually evolving thing in any case.

How Do I use The Whoop 4.0 Strap?

This is perhaps the easiest question of the lot. It’s literally a case of wear it and forget. All the information and insights you want will be on the app, plus some bigger charts and the like on the web platform.

The only two exceptions to the wear-and-forget mantra are when you either want to charge it, remove the strap or broadcast the heart rate somewhere else.


You get the pod, a strap and a cable plus bits of paper you will never, ever read. Charge it up and put it on, you know what to do. It needs to be snug and your hand should definitely NOT turn blue.

Charging Whoop

Just slide the charging cradle onto the strap while you’re still wearing it. Simple! Of course, you can take the band off as well to charge and the cradle itself charges via a USB-C cable.

Whilst the Whoop strap is sufficiently waterproof for pool or sea swimming, the charging cradle isn’t. The charging cradle is splash-proof meaning you could maybe shower with it if you want to.

Broadcast Heart Rate

Whoop App>3 bar menu>Device Settings>Broadcast Heart Rate>Enable

When you enable the Whoop strap to broadcast you will use a tad more battery and you will also have to manually pair it with some other Bluetooth device. You could rename Whoop on that same page and you could connect it to your bike computer or some gym equipment. Simply put, you could broadcast to your Zwift, your Peloton bike or Carol/Nordic Bike or work alongside your RUNN on the treadmill. Used in this way, Whoop is a generic Bluetooth heart rate monitor and will connect to many pieces of sports kit.

Change or Remove the strap eg for Whoop clothing

One end of the strap slides off the Whoop pod and the other end clips on/off. Attaching a different strap is super easy. Maybe you want a different colour of strap? You got it! There are even custom straps available too.

With the Whoop Body clothing options, you can put your Whoop somewhere other than your wrist during exercise and this is generally a good idea. My favourite is to use the Arm Sleeve as this is probably the most accurate place to wear any optical HR tech, including Whoop/Garmin/Polar/Scosche/Wahoo. Special Whoop bras, shorts and tops give you other options too but I just tried the arm sleeve which I am delighted with.

You can take off the metal clasp before inserting the Whoop pod into the clothing but there is no need to do that.

Warning: I wore the arm sleeve in a few positions around the bicep/tricep. I found the sleeve too loose to wear on the forearm (I bought it for the bicep in any case). When I wore it on the tricep it worked fine BUT there wasn’t a line-of-sight to my sports watch, so the signal wasn’t always received and recorded on the watch, the solution to that was to wear the sleeve so that Whoop was on the outer side of the upper arm, the same arm you wore the watch on. Like this…


The Whoop 4.0 App

For a quick overview, Whoop’s app has 5 main sections summarised here with more details following on:

  1. Home – All your current and recent trend data is here on 8 sub-screens
  2. Coaching – Here you get straightforward, actionable advice on how hard to train today and how much you need to sleep tonight. There’s also a dashboard of key health metrics plus access to highly impressive and detailed weekly/monthly performance reports #IndustryLeading
  3. Camera – Take a video overlain with live performance metrics.
  4. Team – Join a team, sports interest or regional-based team and check the awesomeness of your sleep, strain and recovery on the leaderboards. Warning: there are a LOT of awesome athletes on Whoop that are hard to beat and it’s insightful to see how they recover even if you can’t beat their strain scores.
  5. Hamburger Menu – Lots of learning resources & admin stuff is here. There are also limited links to other software like Strava and you can set your Whoop to broadcast HR here too.


Page Layout – Click

Home Screen

The Whoop 4 home screen contains links to over 20 more screens.

The flow works exactly as shown on this 4×2 matrix of screens. Swipe left or right for different views and then up or down for more or less detail…


That’s a lot of information and insight all in one place. But there is more to discover as you delve into the depths of the app. For example, the first screen lets you tap on an activity or sleep period for minute-by-minute information on your heart rate or, in the case of sleep, some quite detailed stats that include sleep disturbances, efficiency, latency and more besides.

Similarly, there is more information linked to on other screens where, for example,  you can change the workout metric that is graphed on the 7-day trends.

Whoop Coach Screen

The Whoop coach advises you on either the strain you should aim for today and/or the sleep you should aim for as recovery.

The strain coach ‘knows’ your optimal level of strain for today based on your recovery, in the example below I can check that I need to aim for a strain of 10.8 today. Now, I can just go ahead and do such a workout or I can use the coach to guide me during the workout. I need to take the app with me to do that and the app essentially tracks a more detailed workout and displays continually updated strain.

Similarly, the sleep coach gives me the headline guidance of needing 7:59 hours in bed. But it can also coach me while I sleep by setting a smart alarm to wake me when I’ve achieved a certain readiness state. Of course, I can also guide Whoop by saying that I just want enough sleep to get by or that I want full sleep to be on peak performance tomorrow.

Clever stuff.

And it’s clever stuff, presented straightforwardly.


The 3rd page, above, is the Health Monitor which gives you a current snapshot of some key bodily metrics like respiration rate, temperature and SpO2. At the bottom of that page is a super-detailed log of those metrics over the last month or so which you might simply be interested in looking at or which might be useful to print & share with a doctor.

You can probably guess some of the contents of The Weekly and Monthly Performance Assessments. You get some good insights from novel ways of displaying some of the strain data and how each workout places you within productive ranges. The Monthly report is more along the lines of the doctor’s health report and is highly detailed and, I must say, professionally presented.

Camera Page

A camera does what you’d expect with some nice touches thrown in to let you add filters and change the metrics that are captured along with that video of you sweating profusely mid-workout.

System/Hamburger Menu

There’s not too much exciting to talk about here except to note that this is the place you rename Whoop for when other devices might want to connect to the heart rate you allow it to broadcast.

If you want to see your data on other platforms, there are connections to Training Peaks and Strava.  For the latter, you can create a custom graphic to display in your Strava feed.



Whoop Widgets

Widgets in iOS are made good use of by Whoop. In this image, you can see how widgets give you key, glanceable snippets of information without the need to open the app.


Whoop 4.0 Strap – Accuracy Summary and Detailed Review

This is a topic that is going to get a lot of people overly excited.

What do I mean by accurate?

Essentially I use the word to mean repeatable and actionable. IE that you can rely on an accurate device over the long term to meaningfully guide your training.

I’m sure that most of us would agree that we can find a reference point to determine the correct HR at any given time (it’s called a Polar H10 chest strap) and such a device can also produce correct RR beat information for HRV. Similarly, we could also find comparators for Whoop’s other data points like respiration rates, temperature, SpO2 and so on.

However, Whoop gives us a ‘Readiness’ Score. But where is the comparator for that? A: There isn’t one that we could easily agree on because there are proprietary algorithms applied to produce vendors’ own readiness scores.

Then we might ask. “What is Strain?”. Those of us familiar with HR Zones and TRIMP could come up with a definition of strain but heart rate zones vary from person to person and could themselves vary based on your fatigue state or whether you’ve just used stimulants like caffeine. Some of those factors are just unknowable by today’s tech.

Then we might want to compare wrist-based optical heart rate with a lab standard HR chest strap. The wrist is an AWFUL position to capture heart rate during exertion so it will be prone to the vagaries of your exercise or the environments you train in.

Here’s what I did



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Whoop 4 Band Accuracy – Bottom Line

Whoop 4 is accurate for sports when worn on the bicep and gives reasonable results at night when worn on the wrist.

If you are concerned about absolute HR accuracy then wear a chest strap 24×7 #Impractical.

Sports – Running & Cycling HR Accuracy

These results show trivial differences between the accuracy of Whoop, Garmin HRM-PRO and Polar Verity Sense. Apple Watch 7 was the worst.

The only criticism of Whoop would be some minor discrepancies right at the start of some of the workouts. As those results are low-level HR, the strain impact is trivial to the point of irrelavency.

Other reviews on Whoop 4 accuracy have found similar results to mine including those on Reddit and in the review from DC Rainmaker.

Sports – Crossfit HR Accuracy

I worked with the YouTube channel FITGEARHUNTER on the accuracy section of this review. He majors on Cross Fit and has performed some more detailed tests just for that sport and he specifically looks at the accuracy of different wear positions. The conclusion is the same though, don’t wear it on the wrist! A further conclusion is that if you really want to wear it on your forearm then the outer forearm gives the best results.

 Wrist Accuracy Forearm Accuracy Bicep Accuracy

Overnight HRV and Readiness Accuracy

As a professional (athlete or coach), it should be obvious that the physiological response is what matters. M Altini

Whoop calculates overnight ‘HRV’ by using a weighted average rMSSD calculation with more weight given to periods of slow-wave sleep. The result is shown as a single nightly figure in the app. This (HRV) value is then just one of several inputs to a wider, proprietary readiness algorithm that gives a continually updating, single figure percentage indication of your readiness to train hard at any given time.

HRV methods from different vendors might instead use an SDNN calculation, or look at a single sample of 1-5 minutes when you immediately wake up, or use multiple periodic measurements from the night.

Similarly, different vendors use different inputs and weights to fine-tune their unique take on readiness.

You might even want to compare any or all of these to how recovered you feel. Which is mostly irrelevant. What is relevant is physically/mentally how recovered you are and, perhaps more so, exactly to what level are these readiness scores a predictor of your peak performances.

But then, perhaps you only aim to peak 3 or 4 times a year. #Shrug.

Maybe rMSSD/HRV itself is a better predictor?

In a nutshell: You really can’t compare any of this data…so let’s do it anyway!

I found no correlation between Oura, Garmin Body Battery or Whoop with a single, waking-HRV reading from HRV4Training with a Polar H10.

Day-to-day correlation (Col 1) and Baseline Correlation (Col 2), using

Caveat: My HRV is genetically low when compared to what I would expect it to be for my age and fitness. I may also have ectopic heartbeats.

Even if I were to add in alternative sources of data like the Apple Watch 7, I suspect that I would find no correlations in this data for me.

I am probably unusual here and other reviewers, scientists and enthusiastic HRV-enabled athletes who I trust, have found correlations eg friends of this site: Human Performance Tuning & Analysis.

Whoop 4.0 – Wider Review Thoughts

My thoughts on readiness accuracy for over 10 years has been to mentally triangulate these three indicators to intelligently arrive at a personal conclusion.

Anecdote: My best ever triathlon performance followed a night of zero sleep. Yet I felt good and my predicted TSB readiness was near perfect. My HRV level was actually pretty good (as I had been tapering) but the full readiness algorithm factored in factors like sleep continuity and duration so the overall readiness score was certainly sub-optimal. Conclusion: The conclusion is NOT that the readiness algorithm was wrong but rather that I would have performed even better had I slept properly, measured readiness is not the sole predictor of performance.


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Whoop 4.0 Review – Strain & Sleep Recommendations – Yet More Thoughts

Whoop’s strain score is algorithmic and ranges from 1 to 21. Thus it’s easy to get a 10 but much, much harder to push a score of 19 toward 20. This seems a reasonable approach to me but I would accept that it might appear to others to too quickly add strain.

I’ve looked at sleep HR/Sleep-Stage data for over a decade and the more I look at it, the less I want of it. It’s all very interesting but once you compare different tech tools you start to realise it’s all often plain wrong. If you are looking for a simple tool that records your hours of sleep then I’m not sure why you would buy into an advanced sports platform like Whoop. If you are an athlete you might be interested in quantifying the amount of deep sleep when your body restores itself physically but if you are a scientific athlete you will look into Polysomnography and realise that EVERY tech gadgets’ sleep stage estimations are inaccurate.

So, I like how Whoop simply quantifies the volume of sleep I should aim for to sit at my desired place on the ‘Get By’ to ‘Perform’ spectrum. That’s useful advice.

Whoop 4.0 Body, Pro & Accessories, Review Highlights

Be different and, at the same time, improve the accuracy of your HR readings.

You can easily customise your Whoop 4.0 experience.

Get extra fabric straps in different colours or, more usefully, get an extra Superknit Bicep Band so that you can switch the Whoop from your wrist to your bicep when your exercise. Shop: Bands



Get some great quality apparel that can also hold your Whoop band. You’ll get MUCH better HR accuracy and you will keep your regular wrist band in a much cleaner and more hygienic state. So I’d recommend either a sports bra, arm sleeve 4.0 or waterproof arm sleeve. Shop: Whoop Body

For a fully-customised look to differentiate yourself from anyone else wearing a Whoop 4.0 you can change the colours of every aspect of the device including the metal. Shop: Custom Bands


Whoop 4 – 10 top Tips

Here are some frequently asked questions and some lesser questions, hopefully, these will help some of you.

Q: Can I use my Whoop 3.0 Bands?

A: Yes. the material is the right width and the fixed metal end of the band, although bigger, will secure the Whoop 4.0. However the end of the band that threads through the space on the main pod new the new removable attachment. So, yes you can use the straps, but there are limitations.

Q: Is Whoop worth it?

A: Yes, good training decisions are priceless.

Q: Can I use Whoop with older Garmin sports watches using ANT+?

A: No. Whoop is not compatible with ANT+. You could buy a 4iiii V100 Viiiiva device to convert the Bluetooth Signal to ANT+…or you could buy a new sportswtach.

Q: What happens if I break or lose my Whoop Strap?

A: If the strap is in any way defective then Whoop will replace it. But if you misuse or lose your strap then you would submit a non-warranty replacement request directly to Whoop

Q: What if there is a Whoop 5? Would I pay for it

A: No. (Qualifying) subscribers would get one for free. Usually you would need at least 6 months of your subscription remaining, although predicting what would happen in the future is impossible!

Q: Is Whoop More Accurate Than a Garmin?

A: Any vendor chest straps will be more accurate than wrist-worn sensors. As I show above in extensive accuracy tests, Whoop is more than sufficiently accurate when worn on the bicep. If you are concerned about high levels of accuracy then you will not use ANY VENDOR’s optical HR monitor for sports on your wrist. It really is that simple. When it comes to resting HR measurements eg whilst at sleep/rest then I’m certainly not convinced of the accuracy of Garmin’s Body Battery and neither are sports data scientists I know.

Q: Where is the most accurate place to wear WHOOP?

A: I’ve not tested all the alternative wear positions with Whoop. Certainly, the bicep is good and my guess would be that the Whoop apparel that places the sensor just about anywhere else have a reasonable chance of being accurate. IDK for sure.

Q: Is it worth upgrading from Whoop 3.0 to Whoop 4.0

A: Yes. Just do it. The only caveat would be original Whoop Pioneer members who may be able to continue indefinitely with their access to the current features on the app without paying a subscription.

Q: Is Whoop better than the Oura Ring?

A: They are different. Oura Ring Gen 3 is a great sleep tracker and it will estimate your readiness from HRV and sleep parameters. However, it is not at all suitable as an athletic-grade activity tracker or HR monitor. ie It cannot accurately measure strain.

Q: Is Whoop better than Biostrap EVO?

A: If you are super sports, then probably not. Biostrap is similar to Whoop but not as athletically focussed and with a less good app. If you are into Biohacking then perhaps Biostrap EVO is for you.

Q: Is Whoop better than the Apple Watch 7?  or Garmin Forerunner, Garmin Fenix, Polar Vantage & Fitbit?

A: Whoop clearly lacks a screen that watches have! If a screen is what you want then don’t buy Whoop. Whoop is a wear-and-forget, unobtrusive band that’s better suited for certain sports and for wearing whilst sleeping. Most major platforms have some form of readiness assessment but with Whoop you get a whole platform that is geared toward readiness and coaching.


Whoop 4.0 Band Review – Take Out

When worn properly, Whoop 4 is accurate for me as a heart rate tracker. Whoop’s prediction of readiness from HRV adds value to my daily training decisions on exactly how hard I should push myself.

Its form factor is ideal for many kinds of sports and for wearing in bed – a watch face can just get in the way sometimes.

It is hard to fairly criticise Whoop. Perhaps the only notable omission that Whoop and all its competitors lack is a proper accounting of strain from pure strength workouts. Whoop’s acquisition of PUSH (2021) will likely correct this as soon as its algorithms are integrated (2022).

The Whoop 4.0 Strap and app is clearly the market leader in its tightly-defined area of competition – wannabe Pro X-Fit athletes. The relatively unique form factor and the superb app will also have wider appeal to athletes in other sports.

Subscription prices always seem expensive, yet if you replace a high-end sports watch every couple of years, the prices are not too dissimilar.

Now, Join Whoop for free. Get a free band, free joining fee and the first of 6 months’ subscription for free. That’s a lot of free. Starts at Eu/$/£18/mo here at:


Best Whoop 4 discount code right now: Free Whoop and a free start on the app. Clicks to your country-specific page on

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