Whoop 4.0 Band

WHOOP 4.0 takes a radically different approach to health tracking: no screen, no notifications, just continuous physiological monitoring. It tracks heart rate, HRV, skin temperature, blood oxygen, respiratory rate, and sleep architecture — 24/7. Every morning you get a Recovery score (0-100%) and a Strain target. Green means go hard, yellow means moderate, red means rest. It removes guesswork from training and recovery decisions. The band is 33% smaller than WHOOP 3.0 and available in multiple wearable formats (wristband, boxers, sports bra, arm sleeve). Battery lasts 5 days and charges while you wear it via a sliding battery pack. Requires membership ($30/month). For serious athletes and health optimizers, the data is unmatched.