Discover the WHOOP Strap 4.0 in this complete review. Learn about features, accuracy, battery life, subscription costs and whether the WHOOP Strap 4.0 is right for you.
If you’re researching the WHOOP Strap 4.0, you’re likely looking for a high-accuracy, data-driven fitness wearable that goes far beyond step counting. The WHOOP ecosystem is designed for continuous performance monitoring — not flashy smartwatch features — and this makes it one of the most unique devices in the fitness technology space today.
Below, we’ll break down everything you need to know about WHOOP 4.0, including its design, sensors, accuracy, subscription, and whether it’s worth buying.
What Is the WHOOP Strap 4.0?
The WHOOP Strap 4.0 is a screen-less, strap-based wearable that tracks your body’s physiology 24/7. Instead of acting like a smartwatch or everyday fitness tracker, WHOOP focuses heavily on three critical areas:
Recovery
Strain
Sleep
Its main purpose is to provide actionable insights into how your body is performing and recovering — giving you a clearer understanding of readiness, rest needs and training load.
How WHOOP Differs from Traditional Fitness Trackers
WHOOP is not a step counter.
It’s not a smartwatch.
It’s not built for notifications, GPS or apps.
Instead, the WHOOP Strap 4.0 acts like a continuous performance lab on your wrist. It’s meant for people who want deeper insight into HRV, sleep quality, recovery patterns and daily stress levels.
Key Features & Technical Specifications
Advanced Sensor Technology
Upgraded LED Array & Photodiodes
Compared to WHOOP 3.0, the WHOOP Strap 4.0 uses a redesigned sensor module including:
- 3 green LEDs
- 1 red LED
- 1 infrared LED
- 4 photodiodes
This setup enhances heart rate accuracy — particularly during workouts.
Added Skin Temperature & SpO₂ Sensors
WHOOP 4.0 introduced two major health-tracking sensors:
- SpO₂ (blood oxygen saturation)
- Skin temperature monitoring
These help the system better assess overall recovery and identify unusual physiological patterns.
Battery Life & On-Wrist Charging
The WHOOP Strap 4.0 lasts up to 5 days per charge, depending on your usage.
Its battery pack is:
- Fully waterproof
- Allows on-wrist charging
- Attaches magnetically
You never need to remove the strap.
Water Resistance & Durability
WHOOP 4.0 is water-resistant and suitable for:
- Swimming
- Showering
- Up to 10 meters for 2 hours
This makes it ideal for continuous 24/7 wear.
Device Size & Wearability
The WHOOP 4.0 is 33% smaller than its predecessor, making it more comfortable for:
- Long wear
- Sleep tracking
- Placement under clothing
It is extremely lightweight and designed to be forgotten on your wrist.
Core Measurements: Recovery, Strain & Sleep
Recovery Score: Metrics That Matter
WHOOP calculates recovery using inputs like:
- HRV
- Resting heart rate
- Respiratory rate
- Sleep performance
- Skin temperature
- Blood oxygen
Your daily recovery score tells you how ready your body is for stress or training.
Strain Tracking for Workouts
Strain shows how hard your body worked today — not just activity minutes, but actual cardiovascular load. It’s ideal for:
- Endurance athletes
- CrossFit
- High-volume training
- Cycling and running
It gives clearer guidance on whether your training is balanced.
Deep Sleep Analysis
WHOOP analyses:
- Light sleep
- Deep sleep
- REM sleep
- Disturbances
- Respiratory rate
This makes sleep tracking one of WHOOP’s strongest features.
Wearing Options: Wrist, Bicep & WHOOP Apparel
The WHOOP Strap 4.0 can be worn:
- On the wrist
- On the bicep with an arm sleeve
- Inside WHOOP Body apparel (bras, leggings, shirts, shorts)
Accuracy Improvements With Bicep Placement
Reviewers consistently note that bicep placement improves heart rate accuracy, especially during:
- High-intensity intervals
- Strength training
- Upper-body movement
WHOOP App Experience & Insights
Daily Coaching & Recommendations
The WHOOP app offers personalised suggestions including:
- How much strain to aim for
- Your ideal bedtime
- Sleep need
- Daily recovery score
- Training readiness
What Makes the WHOOP App Unique
The WHOOP app is the heart of the product — without it, the device would have little value because there’s no screen on the strap.
WHOOP Strap 4.0 vs WHOOP 3.0: What’s New?
Sensor Quality Improvements
The sensor array is significantly more advanced, providing better HR accuracy.
Wireless Waterproof Charging
A first for WHOOP — charging without removing the strap.
Smaller, Lighter & More Versatile Design
The device is 33% smaller and fits more comfortably inside WHOOP apparel.
Pros & Cons of the WHOOP Strap 4.0
Major Advantages
- Excellent for recovery-focused athletes
- Accurate HR and HRV measurements
- Comfortable 24/7 wear
- Detailed sleep insights
- Multiple placement options
- On-wrist charging convenience
Key Limitations
- Subscription required
- No display or smartwatch features
- HR accuracy may drop during explosive upper-body movements
- Recovery score can feel off on some days
Pricing & Subscription Model Explained
Monthly Costs
WHOOP uses a subscription system, with device cost included. Typical pricing:
- 6-month: ~£25–£30 per month
- 12-month: Lower monthly cost
- 18-month: Lowest price per month
Why WHOOP Uses a Subscription System
Because most value comes from:
- Data analysis
- Recovery algorithms
- Sleep insights
- Cloud-based updates
WHOOP positions itself as a service, not a device.
Who Is the WHOOP Strap 4.0 Best For?
Ideal Users
You’ll benefit from WHOOP if you:
- Are an athlete, runner, lifter or cyclist
- Want deep insight into your physiology
- Wear your tracker 24/7
- Value recovery metrics over step counts
Who Should Avoid It
WHOOP is not for people who want:
- A watch with notifications
- A one-time purchase
- GPS tracking
- Step counting as a priority
Tips for Getting the Most Accuracy From WHOOP
Optimal Placement
For strength or high-intensity workouts:
- Use the bicep strap
- Or WHOOP Body apparel
Maintaining Sensor Performance
- Keep the sensor clean
- Ensure snug contact
- Charge regularly using the waterproof battery pack
Summary of the WHOOP Strap 4.0
The WHOOP Strap 4.0 is one of the most advanced recovery-focused wearables available today. Its upgraded sensors, comfortable design, strong app insights and flexible wearing options make it ideal for serious athletes and health-focused individuals.
However, the subscription cost and lack of smartwatch features mean it’s not suited for everyone.
For more information, you can also explore independent testing from trusted reviewers like DC Rainmaker. (external link: https://www.dcrainmaker.com)