The invention of heart rate monitor is to be found in a cold nordic country with a strong ski culture. The first wireless heart rate monitor was invented in 1977 as a training aid for the Finnish National Cross Country Ski team and as ‘intensity training’ became a popular concept in athletic circles in the mid-80s, retail sales of wireless personal heart monitors started from 1983. Strapless heart rate monitors now allow the user to just touch two sensors on a wristwatch display for a few seconds to view their heart rate. These are popular for their comfort and ease of use though they don’t give as much detail as monitors which use a chest strap.