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His Whoop Age was 44
A bad first reading
Kevin Huang got his Whoop last fall, after friends kept talking up the metrics it collects. Owners of the device trade one question whenever they meet: how old are you, and how old does your Whoop think you are? The answer comes from Whoop Age, a number built from sleep performance, resting heart rate, and daily activity. It comes from a consumer product, not a medical device. His first reading was 44, seven years older than he was.
Rebuilding his mornings
He took it as a wake-up call. On workdays he started getting up around 5 AM to do cardio at the gym before work, and he paid attention to his diet, since clean, healthy meals usually lift his recovery score and fried, high-sodium food pulls it down. Each morning the sleep and recovery numbers read like a daily report card on his health, which he finds motivating.
A year later
About a year later his Whoop Age was 35, which put him back in his thirties. He feels healthier, and he is doing it partly to be a more active dad and to live longer.
How does a watch estimate biological age?
Wearable ages are built from signals that track closely with long-term health, mainly resting heart rate, sleep, and activity. Researchers have linked fitness and heart measures like these to how long people live. A 2018 study in JAMA Network Open followed 122,007 patients at the Cleveland Clinic and found that higher cardiorespiratory fitness was tied to lower mortality, with no upper limit to the benefit.
Why does resting heart rate track fitness?
A heart trained by regular cardio grows stronger and pushes out more blood with each beat, so it needs fewer beats per minute at rest. The American Heart Association describes a normal adult resting rate as 60 to 100 beats per minute. Well-trained endurance athletes often sit in the 40s or 50s. Resting rate also rises with stress, illness, and poor sleep.
How do wrist sensors read a heartbeat?
Most wrist devices use photoplethysmography, shining green light into the skin and measuring how much bounces back as blood volume pulses with each beat. In a 2017 Stanford study in the Journal of Personalized Medicine, researchers tested seven wrist-worn devices on 60 volunteers. Heart rate errors stayed under 5 percent for most of them. Estimates of calories burned were far less accurate, with errors as large as 93 percent.
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