Reviewed: Whoop Strap 3

The Whoop Strap 3 promises to help guide rest and recovery, setting it apart from other wearable devices.

Photo: Greg Kaplan

Review Rating


A wearable that tracks rest and recovery, not just rides and other activities, and makes predictions about performance based on rest and recovery analysis.


troves of data and analysis about rest and recovery; ingenious charging method;


optical sensor lacks accuracy

Our Thoughts

The Whoop Strap 3 promises performance improvements based on guiding rest and recovery habits. The amount of data it collects about its wearer is staggering. But the biggest limitation is the lack of accuracy in the technology which collects this data.





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Raise your hand if you have friends who don a wearable without a data display, or have seen this band on the wrists of pro cyclists like the EF Education-Nippo squad. While your hand is raised, look at your wrist. Are you missing something? While you’re wearing the Whoop Strap 3 24-7, it calculates the deficit between physiological expenditure and rest and recovery. The Whoop tells you what to expect from successive rides and other activities based on quality and quantity of recovery and sleep.

What Whoop measures

The Whoop Strap measures all-day strain and compares this against rest and recovery. To further improve accuracy, Whoop lets one journal other factors that contribute to performance through a customizable questionnaire — configurable from a list of questions — presented every morning. This accounts for factors like perceived calmness and psychological stress from the previous day, as well as environmental factors like sleeping in one’s own bed with a partner and/or an animal, and also influencers like time of day and intake of food/caffeine/alcohol and NSAIDs, sleep aids, and more. I see a direct correlation between the quality of sleep and the amount and timing of alcohol ingested. Whoop provides data visualizations so I can compare with how I feel, and how I perform. When I’m feeling fast or slow, Whoop helps to identify patterns for success and avoid ones for failure.

Whoop recovery screens
The whoop app recovery screens. Photo: Greg Kaplan

When I dig into the data collected and analyzed by the Whoop Strap there are a lot of performance predictors based on rest and recovery. I find that some are pretty accurate, while others are less so. All data collected are reliant on the optical sensor, so the information presented is only as good as the accuracy offered by this technology.

One of these things is not like the others

The Whoop Strap 3.0 appears to be pretty simple in appearance. However, after just several days of use, it becomes clear that the data it records and reports are anything but simple. After unboxing, paring it to my phone with the free app, and answering a few questions during the initial Strap setup, I was ready to do nothing with it. The Strap passively collects data in an always-on state. While the app does have options to manually set activity duration, perceived effort, and perceived performance like other tools, it’s not necessary.

The data provided by the Whoop Strap is different from the information provided by Strava’s Fitness/Freshness, which analyzes activities uploaded to it from other devices. A Whoop account can be linked with a Strava account for data comparison between the data analysis tools. The Strap can be set to broadcast its heart rate measurement via Bluetooth that can be received by one’s bike computer, alleviating the need to wear a redundant strap just for heart rate measurement. But the data that the Whoop provides is different information than what is available Garmin Connect, uploaded from my Fenix 6. The Whoop data analysis focuses on rest and recovery, while the other tools provide data that focuses primarily on activities and physical expenditure. Garmin has improved its rest and recovery data capture and analysis, but I think Whoop still leads here.

Whoop tracks metrics when I'm not riding — strain, recovery, and sleep — to make predictions about the level of future performances.
Whoop tracks metrics when I’m not riding — strain, recovery, and sleep — to make predictions about the level of future performances. Photo: Greg Kaplan

Whoop metrics — what they mean

Whoop’s benefit lies in the data analysis from when one is not training. While the strap can automatically detect activities —like rides, weights sessions, etcetera — and score them on their physiological cost, the Whoop Strap continuously measures my condition to account for multiple factors, that affect athletic performance. This includes sitting in an office chair, walking up and down stairs, and even taking a nap.

Before taking action on the data Whoop provides, understanding what is being measured is a necessity for making decisions and taking action based on the data collected.

  • Heart Rate Variability (HRV) measured during one’s deepest sleep, an indicator of ability to perform. According to Whoop, “HRV reflects the extent to which your body is ‘distracted’ with other physiological demands, such as musculoskeletal recovery, stress, illness, and fatigue.” Those who cannot put 100 percent of their resources into performing will be at a disadvantage compared to those who can.
  • Resting Heart Rate (RHR) measured during one’s slow-wave, deep sleep. A lower RHR over time may indicate improved fitness and/or recovery.
  • Strain summarizes the cardiac load from a training activity, and also over the course of a day, based on heart rate measurement. This score is on a scale from 1-21. This score is relative to one’s current level of fitness. This measurement is most similar to those recorded by Strava, Garmin Connect, and TrainingPeaks during activities.
  • Recovery indicates how well one is ready to take on additional strain — e.g., riding — based on a measured, relative return to a rested, baseline state after a ride or training session. Factors that influence recovery are quantity and quality of sleep or downtime following an activity. Whoop uses HRV, RHR, respiratory rate, and hours of sleep to calculate recovery. A high recovery score means one can expect a relatively higher level of performance than if one has a low recovery score. Recovery is graded in three bands broken evenly into thirds and color-coded for simple analysis.
  • Sleep is measured and compared against a recommended amount of overnight rest based on the previous 24 hours’ Strain. Whoop uses an average of 7.6 hours to compare against measured sleep, and compares this against the hours of sleep the Strap detects.

Modular power to go

One ingenious feature that Whoop carefully engineered is the onboard battery. The Whoop Strap battery level is indicated on the app home screen and asked to be charged when the battery reserve dips below 20 percent. I had to charge it about once every 5 days or so, and to do this, I clip on the removable battery pack that delivers a charge to the Whoop. This pack is charged with a standard micro-USB cable. This configuration allows one to wear the strap while charging, and not be tethered to a power outlet. Since the batter is not too bulky, I charge the Whoop while I’m at my desk, on my computer.

Whoop Strap modular battery charging.
Whoop Strap modular battery charging. The red LED indicates batter charging status. Photo: Greg Kaplan
Whoop Strap being charged with its modular battery in place.
Whoop Strap being charged with its modular battery in place. The unlit LEDs on the top left of the battery indicate strap charging status. Photo: Greg Kaplan

Training Whoop

In an initial, five-day learning period, the Whoop analyzes sleep quantity and quality. After 30 days, Whoop has collected enough data about activities, all-day physiological expenditure (i.e., sitting, walking around, climbing stairs, etc.), recovery, and sleep to provide meaningful and actionable analysis. With each additional day of data collected, Whoop builds a more robust and personalized profile on which it sets expectations for performance. Whoop lets me know when I level up, meaning that it has improved its “understanding” of my needs based on the data it collects and compares against my baseline and a database of metrics for other Whoop users in my cohort. Joining groups in Whoop allows comparison against others in similar sex/age/activity groups, for comparative analysis.

Whoop app sleep screens
Whoop app sleep screens. Photo: Greg Kaplan

Of the performance analysis tools I use most frequently — Strava and Garmin Connect — I find the Recovery score in Whoop to be the most accurate predictor of future performance. There’s a very high correlation between what Whoop indicates and how I feel after a night’s sleep, and then on a subsequent ride. On nights when I get less than optimal sleep (about seven to seven-and-a-half hours for me) coupled with a high relative training load from the previous day, I feel like I’m dragging. Whoop predicts a performance dip based on activity and sleep measurement;  a positive correlation is a good reinforcement that I can listen to my body some of the time when I feel under-rested.

And, for the most part, the Strap is frequently accurate.

Informed behavioral modification

The Whoop app (and also the desktop browser view) presents a wealth of data. Taking action based on data presented is the most challenging aspect of using this tool. Changing behavior is hard: Going to bed earlier, backing off training when I’m showing a high Strain score, not having one more pint of IPA when I can clearly see a positive correlation between the timing of alcohol intake and poor sleep are challenges to my routine. I remind myself of the cost of a subscription, as motivation; after all, I’m making these changes for self-improvement, right?

But, one area where all this data is easy to interpret — and relatively easier to make changes — is using Whoop to shape tapering/peaking for performance. When Whoop indicates a relatively lower Strain score and provides feedback that indicates efficient recovery (i.e., decreased training volume and intensity) I know I’m ready to perform. Of course, actually resting and not riding more is hard to do, especially during the summer when friends are riding long and then going for pints after. But, armed with Whoop’s information, I can repeat the behavior that leads to success and try to avoid the ones that do not. And just knowing the Whoop data supports feeling rested and ready to go is a boost.

Whoop poor recovery indication
The Whoop desktop view of indication of poor recovery. Photo: Greg Kaplan

The behavioral changes that lead to peaking are all based on the data collected by the Whoop. And there’s the rub. Not only do I need to routinely provide user input (about all variety of behaviors like eating, sleeping environment, the timing of behaviors, and more), but the technology that passively runs all the time needs to be reliable and accurate.

Accuracy and Strap placement

During my first few weeks using the Whoop with it on my right wrist, I experienced suspect heart rate measurements in contrast to the data collected from my other devices. I compared the data collected by the Whoop — primarily heart rate and respiratory rate — against benchmark data collected from a wearable and chest strap, both of which I know to be accurate.

Whoop respiratory rate.
Whoop respiratory rate. Photo: Greg Kaplan

The Whoop Strap measures my breathing rate while I’m sleeping when movement is least likely to affect Whoop data collection. However, the data collected by a wearable on my other wrist is not in agreement.

Garmin Fenix 6 respiratory rate.
Garmin Fenix 6 respiratory rate. Photo: Greg Kaplan

Putting a longer strap on the Whoop and moving it to my left bicep slightly improved the quality and reliability of the data measured, but I still questioned the accuracy of what the Whoop reports. While I experience less gapping between the sensor and my skin — crucial for accuracy — I’m skeptical that the Whoop is accurate due to collecting data through tattooed skin. The data being reported from all-day-and-night wear does not appreciably change when moving the strap to my bicep, but I snag the Whoop a lot less often compared to when it’s on my dominant wrist.

Comparing the Whoop data against the Wahoo Tickr heart rate monitor strap and a Garmin Fenix 6 wearable I’m convinced that the Whoop on my wrist is not providing me with consistently accurate data. The respiratory rate data collected by the Whoop is generally 2-3 units/minute from the data I have collected from my Fenix, too, which causes me to further question the accuracy of readings from Whoop. While 2-3 units/minute may not seem like a lot while climbing steep hills on the bike when my breathing and heart rates are high, the data is collected while I sleep, when my breathing rate drops below 16 breaths/minute should be more accurate, right? So a variance of 3 breaths/minute is significant by percentage.

Do tattoos pose problems for the Whoop Strap 3 bicep band to get an accurate reading?
Do tattoos pose problems for the Whoop Strap 3 to get an accurate reading? Photo: Greg Kaplan

Riding with the Whoop, and looking at the data it collects, I see that the Strap is not displaying heart rate data similar to those I see provided by my Wahoo or even the Garmin Fenix on my wrist — all very different heart rate monitoring technologies.

Whoop collects heart rate data during sleep and also during activities.
Whoop collects heart rate data during sleep and also during activities. Photo: Greg Kaplan

While the differences between the average heart rates between Whoop (above) and Garmin (below) are similar the data reported about my maximum heart rate are significant. This is important as these data are used for gauging relative exertion, and the recovery needed.

I recognize the heart rate data collected by Garmin to be relatively accurate, based on years of data collection across different devices and technologies.
I recognize the heart rate data collected by Garmin to be relatively accurate, based on years of data collection across different devices and technologies. Photo: Greg Kaplan

Whoop wish list

The Strap can broadcast heart rate. If the Strap could be paired with a third-party chest strap for use during riding or other activities, I think that the accuracy would be greatly improved, and the Whoop Strap might provide an even better picture of rest and recovery, retrospectively.

Also on my wish list for Whoop is the ability to use a third-party device to collect data and upload it to the Whoop app or website. The data analysis provided by Whoop is valuable to be sure, but with the increased accuracy provided by a chest strap heart rate monitor, the subscription service would be even more valuable.

If Whoop can solve the optical heart rate monitoring (and other data collection)  issue by allowing third-party data collection on the Whoop app or website, or allow for pairing with an external heart rate monitor, the value of the data analysis and recommendations provided by Whoop would improve by orders of magnitude.


The power of the Whoop Strap is the data analysis surrounding rest and recovery, which is different from other performance monitoring tools. The data Whoop collects when I’m least active seems to be most accurate, but so, too, is the converse. When Whoop analyzes resting data and compares it against activity data, both data sets need to be accurate if the data analysis is to accurately predict future performance.

The one caveat — and it’s a big one — about the data collected by Whoop is the quality of data being collected is reliant upon the optical heart rate sensor technology. While the Whoop sensor is higher quality than many wearables and provides similar data as reported by the latest generation of Garmin wearable devices, it is still not as reliable as wearing a chest strap heart rate monitor.

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