Whoop 4.0 fitness tracker review: A trainer’s tracker

In a world of increasingly elaborate fitness gear, Whoop hones in on the original promise of the fitness tracker: optimizing your workouts. Both a data analysis service and a physical device, Whoop delivers bountiful biometrics and analysis for athletes and dedicated fitness enthusiasts before, during, and after exercise through a dedicated fitness tracker you wear on your wrist and a companion app on your smartphone.

The company’s latest device, the Whoop 4.0 fitness tracker, is more compact than previous generations while introducing more functions. It might not look like much at a glance but, within just a few weeks, it quickly becomes a powerful ally in your fitness life, providing greater insight into performance and recovery, allowing you to maximize the efficiency of your workout routine. Between the lack of lifestyle features and specificity of the data, the Whoop 4.0 won’t necessarily help casual and/or inconsistent exercisers. If fitness is a big part of your life, though, the detailed information it shows can really help you push your workouts to the next level.

Nick Hilden

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The two Whoops

It’s virtually impossible to separate the features of the Whoop 4.0 tracker and Whoop, the fitness-tracking service. Unlike most fitness trackers, which you purchase and use at will, Whoop charges a monthly subscription for access to its services—$30 per month or $324 for 18 months up front. When you’re subscribed to the service, Whoop sends you the latest Whoop strap for free and will replace it when/if they release a new model. According to the company (also called Whoop), the subscription model allows it to provide more in-depth tracking, including highly accurate data tracking and analysis that will help you train smarter, access to expert-created fitness resources, and inclusion in a social community of similarly focused athletes.

That makes Whoop feel like a commitment, and it’s meant to. To get all the data it needs, you’re expected to wear the Whoop 24/7. In exchange, you get a variety of information about your body activity: calorie burn, sleep quality, workout strain and recovery, respiration, blood oxygen levels, and more. Like other trackers, it pays special attention to workouts but, while most trackers emphasize analysis during performance, Whoop is the rare product to take a closer look at post-performance recovery.

It allows you to track a wide variety of specific workouts that you would expect, like running, weightlifting, and boxing, but it veers into more surprising territory by tracking activities like circus arts, parkour, pickleball, and even caddying. It is waterproof down to 10 meters, enabling tracking for swimmers and ensuring that you can leave it on in the shower.

Form over function

As for wearing it 24/7, I found the Whoop 4.0 tracker’s lightweight, minimalist design comfortable to keep on for long periods of time. Its slim, barebones design is light enough that you’ll forget that it’s there but it also offers a sleek aesthetic that looks more like a decorative wristband than a fitness watch. I personally find that low-key look preferable to some of the more tech-forward trackers, which remind me of a video watch in an episode of “Inspector Gadget.”

Whoop’s tracker isn’t totally ignorant of style (or of the potential to charge extra for accessories). Whoop sells custom tracker bands with a fairly wide range of loop and clasp color options to choose from. Since the Whoop’s style is very simple, there isn’t much variation beyond customizing a few small components but you can absolutely buy extra Whoop bands to fit your personal style.

The initial launch process for the Whoop 4.0 is fairly straightforward. All you need to do is pair it with your phone using the companion app rather than your Bluetooth settings, then enter some basic personal information and you’re ready to Whoop it up.

According to the company, the Whoop 4.0 tracker will operate for as long as five days on a single charge, which matches my experience using the tracker for a little over a month. You charge it using a snap-on, waterproof battery pack, which can top off the tracker quickly in quiet moments during the day, like when you’re in the shower or washing dishes … assuming it works. The battery pack charged inconsistently: I frequently had to disconnect and reconnect it multiple times to make sure it actually charged the tracker. Under ideal conditions, it charges quickly—a little over an hour to get a full charge—not factoring in the time it takes to ensure it’s working correctly.

Luckily, the Whoop’s charging complications are an isolated problem. The app is about as easy to use as they come. While I’ve tried other tracker apps that leave you digging for information, Whoop’s is intuitively organized and it shouldn’t take you long to understand where everything is located. All of the key metrics relating to sleep, performance, and recovery are front and center and more nitpicky details—like blood oxygen levels, respiratory rate, and skin temperature—are readily available if you want them. Some apps overwhelm you with data, but Whoop doesn’t feel that way.

It takes time for Whoop to gather enough data to show the full depths of its insights. From the get-go, it provides the basic data points, such as calories burned, but it needs to register a few “recoveries” (nights of sleep after a workout) before it provides more elaboration. After a week, for example, it will inform you about the quality of your exertion vs. the quality of your sleep, then as weeks accumulate it will compare the most recent week against the past. My latest week boasted “optimal” strain while, apparently, my “sleep could use improvement.” Sounds about right.

What can you do with a Whoop?

The Whoop tracks a lot of different physical metrics but I was particularly interested in three: calories burned, strain vs. recovery, and sleep.

The Whoop 4.0 nails the basics. While most calorie counters tend to dramatically over or under count, the Whoop seems to be right on the money, consistently matching my own manual daily monitoring. Counting calories is a basic building block for fitness tracking: It’s essential for fitness enthusiasts looking to maintain an accurate calorie deficit or surplus in order to burn fat or build muscle. That Whoop does it so well automatically puts it in the pantheon of biometric tracking with the best fitness trackers.

Over time, Whoop uses the biometric data to generate broader insights. The service breaks these insights into workout-focused, or “strain,” analysis and non-workout-focused, or “recovery,” analysis. The goal here is to optimize your workouts by pushing you to your limits (when appropriately recovered), then making sure your body gets fully rested before you push yourself again. During workouts, you get simple strain data fed back to you in real-time, followed by analysis after the fact. Information about your strain and recovery is presented via easy-to-understand graphs and charts, including sleep-related data that’s available each morning.

Whoop uses this data to provide information about the quality of your workout and recovery. On good days it might be “optimal” while if you’re exercising at a more casual pace, it might deem your efforts merely “restorative.” It can also warn you when you’re overreaching, especially in relation to your state of recovery. I have certainly noticed that when my sleep is in the red, literally displayed in the form of red bars on a chart, my workout performance suffers.

Those insights make the Whoop a very good training tool if you’re trying to get faster or stronger. When working out I might think that I’m giving it my all, then I look at the app and find that I’m only attaining a somewhat low percentage of my potential. I push myself harder and, lo and behold, it turns out I had more to give. In that way, it functions much like a trainer, but a trainer that can actually see into your body and know how much it has left in the tank.

After using it for a few weeks, I’ve noticed a substantial difference in my performance. The Whoop tracks your physical exertion throughout the day but you can also engage it in tracking a specific physical activity, such as running, weightlifting, or whatnot, and it will tell you how hard you’re working. During the activity, you keep an eye on that strain rating, then push yourself accordingly.

Between workouts, Whoop gives you advice on how to best let your body recover. This is largely based around the quality of your sleep, which it tracks and presents on a graph using metrics like time in bed, disturbances, time in REM and deep sleep, and more. Generally, it uses this data to tell you when you need to get more sleep and/or slow down in workout to give your body time to recover.

After it has collected roughly a week’s worth of “recoveries,” it will also provide recommendations about when you should be going to bed and waking for optimal recovery. If you want to be 100% recovered but need to be awake by 8 am, for example, it will tell you when you should go to sleep in relation to how hard you’ve been training. It also has a built-in alarm that will vibrate gently to wake you when you’ve reached your recovery goal or waking time.

For me, the “Sleep Coach” turned out to be a game-changer. I’ve long struggled to get fully rested regularly. While I was aware of the problem, seeing the issue quantified and tied to my fitness really helped me understand where I’ve been falling short. Now I can look at the Whoop app and know that, due to a hard day’s training and a few nights of subpar sleep, I should go to bed earlier—providing a specific window for sleep that will provide optimized recovery for training the following day. It also makes me aware of when I’ve been pushing my body too hard and of when I should perhaps take it easy at the gym, or take a day off altogether.

In addition to analyzing your data on its own, Whoop offers some services to help you put that data in context. First, “Teams” is a community section that creates leaderboards for different groups of members. You can see how your strain, recovery, and sleep rank among specific niches, like weightlifters, 30- to 40-year-old men, soccer players, runners, and so on. If you need a little competition to spur you on, it’s available any time.

Whoop also offers a series of expert-led discussions and other resources to help you understand the data Whoop provides. There are articles covering data points like blood-oxygen levels and heart rate, as well as general tips for improving your Whoop performance, including how to sleep more soundly. You can also ask the experts directly in AMA-style group chats hosted by Whoop.

So, who should sign up for Whoop?

Whoop is a fantastic service for athletes and fitness fans who really want to push themselves. The Whoop 4.0 tracker provides a robust set of data and finds ways to help you push yourself harder when you work out. The “strain” vs “recovery” data, in particular, makes it very easy to get a sense of how hard you should push yourself, and how often.

While this kind of analysis doesn’t offer much value to casual gym-goers or athletes, for dedicated gym enthusiasts who are looking to elevate their performance to the next level or competitive athletes seeking to maximize their training, this sort of info can provide the edge necessary to achieve the utmost in gains, shred, or speed.