I’m just curious how the technology works. I’m assuming that WHOOP detects my sleep when my heart rate goes way down when I sleep and way up when I work out hard, but I’d like to know a bit more as to how specifically that works. Also, I was surprised to see it recognized when I was playing tennis… how did you know I was playing tennis vs. running?
The WHOOP strap has many sensors that capture information about your physiology and movement. Two key sensors for detecting activities such as sleep and workouts are the photoplethysmography (PPG) sensor and the inertial measurement unit (IMU) sensor. Ever notice the green light that’s on the bottom of your WHOOP? That’s shining a specific wavelength of light into your skin that will be absorbed by the blood in your skin’s capillaries. Between the green lights are two photo receptors that measure how much light is reflected back or absorbed, which allows WHOOP to measure many things about about your cardio-respiratory system. In addition to this, the IMU sensor tells us how your WHOOP strap (and thus your body) are moving through space. The data from these two sensors is fed into machine learning models that have been trained to detect activities using data collected at WHOOP Labs and with our partnering institutions like Central Queensland University and University of Arizona.