A device that measures a wearer鈥檚 heart rate; particularly useful for monitoring exertion in athletes. Finnish professor and nordic skier , the Polar Sport Tester PE2000. It debuted in 1982 and was made up of two pieces: a simplified EKG- and radio-equipped strap worn around the chest, and a wristwatch that received the data and displayed an athlete鈥檚 pulse in real time.
The PE2000 is credited with giving rise to high-intensity interval training鈥攁nd launching decades of R&D to find some alternative to eliminate the dreaded chafing that comes from wearing the strap (a.k.a. the 鈥渕an bra鈥). The most promising solution, the optical heart-rate sensors embedded in watches from , , and others, uses LED lights to illuminate blood vessels and a sensor to detect the volume of blood flow. To date, these devices have proven far less accurate than S盲yn盲j盲kangas鈥檚 original, though many offer users the ability to unobtrusively gather heart-rate data around the clock.