The Whoop 4.0 fitness tracker measures SpO2, pulse and more as a bracelet or in special clothing

Whoop has announced version 4.0 of its eponymous fitness tracker. Like before, the Whoop 4.0 can collect heart rate, blood oxygen, skin temperature, and other vital signs. Supposedly, the new model contains more LEDs, five to be precise, allowing it to track heart rates more accurately.

Whoop 4.0 also offers sleep tracking and can tell people how much sleep they need. Similarly, an integrated stress coach should help you coordinate rest phases and training sessions, should you need help with that. The Whoop 4.0 retains its predecessor's excellent battery life, at up to five days, and its novel charging method. In short, the Whoop 4.0 can recharge via a waterproof battery that you attached while wearing the fitness tracker.

Additionally, the Whoop 4.0 can be worn without a bracelet, unlike its predecessors. Whoop has achieved this by developing Whoop Body, sportswear that allows you to holster the fitness tracker on your body. Whoop plans to offer leggings, sports bras, t-shirts, shorts and underwear under its Whoop Body brand. The company notes that the Whoop 4.0 requires skin contact to work, so it cannot be attached to outer clothes, such as a jacket or a hoodie.

Whoop does not sell its fitness tracker directly. Instead, you can only acquire it via a subscription service that Whoop sets at 6, 12 or 18-months. Currently, Whoop has priced these tiers at US$30, US$24 and US$18, respectively. Existing Whoop subscribers with at least 6 months' membership can request a Whoop Strap 4.0 for free. The Whoop 4.0 will begin shipping on September 27 in multiple markets.

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