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19 Nov, 2023
9 min time to read

This gadget analyzes your activity, sports, and sleep. But what's the purpose?

In search of the ultimate solution for tracking my activity and physical exertion, I came across an interesting gadget — Whoop 4.0. A fairly popular fitness bracelet worldwide promises to analyze all your activity and share tips on optimizing it for $20 per month. After a month of use and complete calibration of the bracelet, I'm ready to share my impressions with you.

The gadget is free, but you need to pay.

Typically, the purchase of a modern gadget is divided into two stages. The first is acquiring the device itself, such as an Apple Watch. The second is purchasing additional services and software for it, such as subscriptions to Fitness+ and sleep monitoring apps.

I've long been accustomed to this type of consumption, and with this approach, one can expect that the device will perform some basic functions without additional purchases. Pay once, and you can potentially use the gadget for its entire lifespan. However, Whoop has chosen a different model, which turned out to be new to me.

The device itself is given for free, and in Europe and the USA, you can get the gadget with a free month of access for preliminary testing. After that, you'll be offered to buy one of three types of subscriptions:

  • Annual subscription — $239;
  • 2-year subscription — $399;
  • Monthly subscription — $30 (minimum subscription period — one year).

The last option is the least cost-effective, as you'll have to overpay $121 for not wanting to pay for the annual access in advance and in one go. And of course, the best value option is the 2-year subscription.

The idea is, at the very least, intriguing. By the way, all owners of Whoop 3.0 received Whoop 4.0 for free, and the company promises to continue updating devices for community members at no extra cost.

In theory, this subscription model can pay off, considering the natural wear and tear of the device and its battery. And Whoop supposedly provides a lifetime warranty, but it doesn't cover stolen or lost gadgets. However, in other cases, the manufacturer promises to repair or replace the device.

I bought my Whoop in Dubai, and by the way, there's no free monthly subscription for residents and guests of the UAE, so I had to immediately pay for the annual plan.

Well, a bracelet is just a bracelet...

Whoop 4.0 comes in a small black package that resembles a set with disposable forks and spoons. It contains:

  • Activity tracking sensor;
  • Charging cable;
  • Charging module.

The sensor itself is a small black rectangular brick that attaches to the bracelet. No displays, the sensor has only one LED on the left side, flashing with three colors: green, yellow, and red. They turn on with a double tap to show the battery level. Whoop's philosophy is not to distract you with a screen, but to focus on the workout.

The key sensors are located on the bottom side — these are 5 LED sensors and 4 photodiodes that collect user data. Specifically:

  • Heart rate;
  • Breathing rate;
  • Blood oxygen saturation;
  • Body temperature.

Based on this data, the bracelet creates a large number of diagrams and compiles various parameters, but more on that later.

And now, about the charging device. It's important to note that, according to Whoop's philosophy, this device is something you never have to take off, even for charging. Therefore, a special charging module is included in the package, resembling a wireless power bank in some way. To charge Whoop 4.0, you need to secure it in special brackets on the bracelet without removing it from your wrist. If the module itself is discharged, you can charge it via the USB-C port, which is very convenient.

There are plenty of band options to choose from — a total of 64 combinations. Being the most creative guy in the editorial office, I chose black. Overall, it turned out to be a good choice. The process of replacing the band is quite fast, and the device is securely fixed. The main thing is to adjust the tightness so that the bracelet doesn't swing on the wrist but also doesn't squeeze it.

Moreover, you can secure the device on various parts of the body. Numerous fixing options are sold separately for this purpose: an arm sleeve for running, special swim trunks, underwear, body kits for women, and so on. However, it should be noted that sensors won't be able to accurately read body metrics through tattoos.

The device is extremely lightweight and is not noticeable on the wrist. As for the build quality, I wouldn't say it's premium. Everything feels a bit fragile, and every time you open it, there's a feeling that the fastener is about to break. The bracelet material is pleasant and didn't cause allergies even with constant wear. A mild rash appeared only after I took a shower with the bracelet several times without properly drying it.

Therefore, I recommend always wiping the bracelet after a shower or swimming. Also, after each workout, it's advisable to clean both the bracelet and the sensor with spirit. These simple hygiene rules will make your life easier later on. And by the way, this applies to any other wearable devices.

What parameters does Whoop measure?

The main sensors of Whoop focus on measuring the major parameters of the cardiovascular system. Simultaneously, due to the presence of motion sensors, many other data are collected, which are then sent to Whoop's servers, where they are analyzed and presented to the user in the form of visual reports.

It's important to note that, for the bracelet to accurately upload the metrics, it needs to connect to a smartphone at least once every three hours.

In the interface of the companion app, metrics are organized into three key groups: sleep, recovery, and workouts. Let's talk about them in more detail.


It's no secret that sleep is considered a fundamental parameter for a healthy body. The duration, quality, and efficiency of sleep are crucial for building a workout program and daily activity.

In a separate tab called "Sleep," the Whoop app shows how much you slept and how much sleep you needed, as well as key sleep parameters:

  • Sleep regularity: The more frequently you go to bed and wake up at the same time, the better your circadian rhythms are tuned, and the better you recover.
  • Sleep quality: Determines the percentage of effective sleep. This is the amount of time your body was able to restore its resources and be ready for further tasks.
  • Sleep debt: Based on calculated data about the required sleep time and actual sleep, the app shows a graph of the debt to your body.

Before each sleep, the Whoop app calculates the required sleep time for you today based on your activity level for tomorrow. You can choose from three parameters: peak, 85% recovery, and 70% recovery. Based on these and your daily activity load and sleep debt, the app calculates how much time you should spend in bed.

The bracelet automatically tracks sleep — you don't need to manually start this activity. After the morning analysis, you receive a notification about sleep quality and a forecast of the activity level for today. Every morning, the app suggests a short questionnaire, asking if you consumed alcohol or caffeine, stared at your phone in bed, and so on. This is to track harmful habits and help combat them in the future.

I compared the sleep analysis quality with the Apple Watch — Whoop 4.0 records about twice as much deep sleep, and the other measurements are more or less identical. Of course, Apple Watch lacks smart analysis algorithms and recommendations; the watch can't differentiate between useful and "junk" sleep. But these are the things that organize my activity. And now I try to rely on Whoop's metrics and advice, which gives a noticeable positive result in terms of well-being.

The bracelet also has an alarm clock. You can set it for a specific time, completion of the sleep quality plan, or recovery level. The vibration motor quality is low; it's not at the level of the Apple Watch's awakening. To turn off the alarm, you just need to tap the device twice.


This is a combined parameter that, based on data about the respiratory and cardiovascular systems during sleep, outputs a certain percentage. Using this, the bracelet sets the optimal activity level for today.

Key Parameters:

  • Heart rate variability: Measures the time difference between heartbeats during sleep. Generally, the higher this value, the better the body is adapted.
  • Resting heart rate: The average number of heartbeats during rest. The lower this parameter, the better the heart muscle functions.
  • Respiratory rate: The number of breaths per minute during sleep.


A parameter directly influenced by the first two indicators, it contains minimal data. It calculates the degree of activity based on the number of calories burned and average pulse. Interestingly, this parameter is also calculated for each initiated workout.

To start an activity, press the plus button in the corner of the screen and start monitoring. There are numerous activities available — from a simple walk to horseback riding and watching TV. Regarding the accuracy of activity measurement, unlike the Apple Watch, Whoop 4.0 checks heart rate much more frequently.

During strength training, it underestimates the number of burned calories compared to watches, but during treadmill walking, it increases. However, the average calorie expenditure for two workouts was the same on both devices.

I like Whoop's philosophy of "not being distracted by the device," but still, it has its drawbacks. For example, during a regular strength workout, it's crucial to record the time between sets for rest, and if with the Apple Watch, you can simply ask Siri or start the timer yourself, it's not possible with Whoop 4.0.

Currently, the timer is the only necessary tool that, in my opinion, is lacking here. But runners might argue with me: they care about speed, pace, and other parameters, and in Whoop 4.0, they can't see them either. Probably, they need something more specialized and with a display to see the metrics here and now without looking at the smartphone.

Additional measurements and features

Stress level: Measures your stress level throughout the day and shows how long you've been in high stress.

AI assistant: Integrated into all app screens, helps analyze data and also has a chat window. Something like ChatGPT.

Training programs: Inside the app, there are many basic workout programs with tips on how to perform exercises correctly.

Communities: An additional element of socialization that helps compare your results with other users.

Photos and videos for social media: A feature that allows you to record content in "story" format, showing key workout parameters and pulse.

Weekly and monthly statistics export: You can get a full report for a week and a month and, for example, send it to your trainer, who can analyze the intensity of your workouts and rest afterward.


Whoop 4.0 is a very intriguing device that helps monitor daily activity and thoroughly track workouts and sleep. Can you sleep and train better without it? Of course. But if you don't want to focus on when you need to go to sleep and, in general, don't trust your feelings, it's still better to get a device like this or similar.

However, the main thing to understand is that the bracelet won't sleep, work out, and eat correctly for you. Yes, it can help in some aspects and adjust your rhythms. Still, the foundation of your healthy body and spirit is only you.