In 1998 Polar launched a new model of heart rate monitors called Polar Smart Edge. This monitor has a new function called Own Zone. This function helps people to find the right intensity zone for aerob training by measuring the heart rate variability.The purpose of our study was to investigate whether this Own Zone function is valid for a group of physical fit men in the twenties.Ten physical fit men in the age between 23 and 27 years participated in the study. They accomplished two tests on a threadmill, and it was investigated at what percentage of the maximal oxygen consumption and the maximal heart freqency the Own Zone set in. During the first day they also tested their maximal oxygen consumption and maximal heart freqency.Polar claims that the Own Zone sets in at about 60-65% of HF-max or 50-55% of VO2-max. The Own Zone set in at 0 of 18 tests (0%) in the 50-55% of VO2-max, and 8 of 18 (44%) tests in the 60-65% of HF-max. The results from this study cannot confirm that the monitor finds the training zones at these intensities. Polar Smart Edge`s Own Zone function is not valid for a group of physical fit men in the twenties.