Whoop Strap 4.0 announced with smaller design and new tracking sensors

Enlarge / The new Whoop Strap 4.0.


Subscription wearable-maker Whoop just launched its successor to the 2-year-old Whoop Strap 3.0. The Whoop Strap 4.0 doesn’t depart from the company’s core goals, aesthetics, or subscription model. Instead, the performance-focused training device gains blood oxygen and skin temperature monitoring for more accurate health tracking.

Like all Whoop Straps before it, the Whoop Strap 4.0 comes free with a subscription to the Whoop app. Starting at $18 per month for 18 months (you pay more for shorter subscription terms), the service offers deep, personalized training metrics, analysis, and guidance focused on training load, rest and recovery, and avoiding injury and overexertion.

The Whoop Strap itself is only meant to collect data. That means there are no screens, no buttons, and no vibrations. The device is simply an observer, and the latest version has shrunk 33 percent while adding SpO2 and temperature sensors into the mix.

Also in this array is an optical heart rate sensor, an accelerometer, and an improved battery to power it all. The company says the new silicon anode battery has 17 percent higher energy density than the Whoop 3.0, but that won’t translate to longer battery life than the five days the Whoop 3.0 offered.

Like the Whoop 3.0, the 4.0 can utilize a clip-on battery pack to power up the Whoop Strap while you’re wearing it. Unfortunately, old versions won’t be compatible with the new Whoop 4.0 due to changes in form factor.

Whoop hasn’t offered specifics on how data from the new blood oxygen and temperature sensors directly impact the accuracy of its wellness recommendations, but the company told us that there are more sensors, “five LEDs (three green, one red, and one infrared), four photodiodes, and advanced algorithms to provide even more accurate heart rate measurements.”

Blood oxygen and body temperature metrics, considered together and separately, can also be useful in assessing your sleep patterns and bodily stress. Whoop uses these two areas to inform its recovery and “strain” scores, which tell athletes when their bodies are best primed for training (and at what intensity level). This training feedback has long been Whoop’s priority, and it’s a feature Fitbit only recently introduced with the Charge 5.

The Whoop 4.0 gathers data to inform wellness guidance shown in the Whoop app. The recommendations are focused on three main areas: sleep, recovery, and training. Metrics like your respiratory rate, calories burned, heart-rate variability, resting heart rate, and sleep performance go into creating separate recovery and strain scores, according to the company’s website.

Sleep tracking uses stages, disturbances, efficiency, and respiratory rate to assess sleep quality. Taking each night’s sleep quality into account, Whoop evaluates overall sleep trends in duration and consistency to give a broader view of sleep quality. Sleep data is considered in the strain and recovery scores, but strain can also inform guidance on sleep—by recommending more sleep on high-strain days, for instance.

The app also keeps track of your “sleep debt,” although the concept of rectifying this imbalance isn’t quite as straightforward as making up lost sleep hours. Rather, studies show that it can take days or weeks of sustained optimal sleep to recover from any “debt.” As such, it’s best to use the “sleep debt” info as a general marker of sleep quality.

The company has also launched a new metric dashboard, called Health Monitor, which compiles your live heart rate, skin temperature, blood oxygen, resting heart rate, and heart rate variability (i.e., the intervals between your heartbeats) on one screen. As with Apple Health, Fitbit Premium, Google Fit, and Garmin Connect, you can export your wellness trends and present them to a physician.

New ways to wear Whoop and perks for “pros”

Alongside the Whoop Strap 4.0, Whoop is launching a line of apparel called Whoop Body. The clothing line includes bras, underwear, shirts, and leggings with pockets for the device. The collection is an expansion on previous offerings limited to arm bands and sleeves. Whoop says a “novel location detection technology” identifies the Whoop’s location on the body.

Whoop is also introducing an add-on to membership, called Whoop Pro. The $12 monthly upgrade (paid in addition to the regular subscription) gives subscribers free shipping, 20 percent off all items, early access to feature releases, and one free item every three months. This bonus item could be a free wrist or arm band, batteries, sleeves, or Whoop Body apparel.

The Whoop Strap 4.0 and Whoop Body are available now on Whoop’s website. Membership comes in six-, 12-, or 18-month terms, for $30, $24, or $18 a month, respectively. Current Whoop subscribers with at least six months of remaining membership are automatically eligible for a free Whoop Strap 4.0. Members with fewer than six months of membership remaining will need to extend their terms. Orders will ship the week of September 27.

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