Carpe diem (and noctem) with Whoop 4.0.

Whoop 4.0 in tandem with the Whoop app helps members unlock less stress, better sleep, and everything in between.

Written by
Nicolette Roux
Man wearing whoop4 0
Source: WHOOP

Note: BodyStack does not accept affiliate marketing commissions on any product. We believe in this product, and this recommendation comes from a good place.

Whoop 4.0 is the comfiest fitness band on the market. Considering how many health and fitness wearables there are — that's really saying something! This low-profile, health and fitness tracker works in tandem with the Whoop app to track key body metrics like Sp02, skin temperature, and heart rate to help you carpe diem and fully optimize both day and night.


  • Extremely comfortable 
  • Waterproof
  • Wireless charging
  • Tracks key body metrics


  • Not as slim as expected
  • Ok battery life
  • No step tracking
Man doing excercise while wearing whoop 4 0
Source: WHOOP

One of the coolest things about Whoop 4.0 is that it's waterproof and supports wireless charging. All you have to do is snap on the waterproof battery pack and you can charge and continue to track your stats in the shower, pool, or while washing the dishes. Carpe diem with Whoop 4.0! 

Product Specifications

  • In the Box: You'll receive an Onyx Whoop 4.0 band and battery pack. Plus, unlimited access to the Whoop app.
  • Size: Whoop 4.0 measures 1.5-inches long by 1-inch wide, by 0.5-inches deep.
  • Battery life: Four to five days on a full charge. 

What We Like About Whoop: 

  • Extremely Comfortable: Whoop is extremely comfortable to wear. It's designed to be worn non-stop, 24/7, thanks to its new, durable SuperKnit band.
  • Waterproof: The Whoop 4.0 sensor and charging pack is IP68 dustproof and water-resistant at depths up to 10 meters (roughly 32 feet) for up to two hours, so you can continue to capture data without interruptions in the shower, ocean, and pool. 
  • Wireless Charging: The Whoop 4.0 charging back takes two to two and a half hours to fully charge itself and your Whoop. You can snap the battery pack on while you're wearing Whoop 4.0 for uninterrupted metric coverage, and your Whoop band will provide up to five days of battery life when charged 100%.
  • Tracks Key Metrics: Whoop tracks your live heart rate (HR), respiratory rate (RR), resting heart rate (RHR), and heart rate variability (HRV). It also tracks your pulse oximetry (Sp02) and skin temperature.

What Might Deter You About Whoop: 

  • Not As Slim As Expected: Whoop has a bit of girth to it. It extends half an inch from the wrist. It's not as slim as most expect it to be. Photos give the impression that it's slim as a band and ultra-low-profile, but it does extend from the wrist to accommodate the sensors. 
  • OK Battery Life: In the grand scheme of battery life, Whoop 4.0 does ok. It offers up to four or five days on a full charge, whereas similar wearables offer up to 10 days or more when fully charged. 
  • No Step Tracking: Whoop 4.0 does not track steps, which might be a disappointment to some. 

The Thought Behind the Product: 

Whoop 4.0 is designed to be worn non-stop and utilizes five LEDs and four photodiodes to capture your data more often than most wearables, providing the best in-class accuracy validated in lab studies and with third-party testing.

It's ultra-comfy and tracks the metrics that matter.

Its IP68 waterproof rating ensures you'll track your data around the clock, whether you're in the shower, pool, or washing the dishes. Plus, its snap on battery pack ensures you never miss a beat day or night.

Whoop 4 0 bands
Source: WHOOP

The Whoop App delivers personalized insights and actionable feedback based on your unique data, behaviors, and goals. To take the guesswork out of your training, you'll receive a Strain Target. Based on your recovery, you'll get a daily target exertion goal to help you avoid overtraining and undertraining.

Whoop 4.0 also acts as a sleep planner.

It measures your sleep patterns and debt, so you know how much sleep you need. Sleep Planner can even wake you when you've reached optimal recovery. Set a haptic alarm that gently vibrates to wake you at the optimum time based on your sleep needs and cycles.

Whoop 4 0 band
Source: WHOOP

Use your Whoop behavioral journal to track daily behaviors like diet type, stress levels, and caffeine intake to understand which behaviors impact sleep and recovery most. Utilize your Whoop 4.0 data, insights, and recommendations to optimize your day and get your best sleep.

Bottom line: 

Whoop 4.0 and the Whoop app are here to ensure you optimize your day and get your best sleep ever. Your Strain Target guarantees you're not overtraining or undertraining. Your Sleep Planner tracks your sleep metrics and wakes you at the optimal time so you can rise feeling refreshed and ready to tackle the day. Your Behavior Journal tracks the daily behaviors that make a difference in your sleep and recovery so you can stress less and get better rest. Carpe diem and noctem with Whoop 4.0 — the best way to make the most of your day! 

Nicolette Roux Profile Image
Nicolette Roux Certified Yoga/Barre/Cycling/Climbing Trainer
Nicolette is a freelance writer, health and fitness expert, and instructor, with over a decade of high-level experience. She’s quadruple certified (yoga RYT-300, indoor cycling, barre, and vertical climbing) and has had the pleasure of working with some of the top studios and brands in the business throughout her career. A devout fitness enthusiast, Nicolette loves being the first to check out and review new industry trends — apps, equipment, athleisurewear, and gadgets. Her work has been showcased on many online platforms including BodyStack, Sports Illustrated, iMore, Android Central, ACTIVE, Journey Commerce, and Crackberry. A modern Renaissance woman, Nicolette also works as a professional performance artist, DJ/MC, and mom to three: 1 human, 2 fur.
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