The Mercury makes it possible under certain assumptions to determine the approximately max. cardio respiratory efficiency (VO2 max) and therefore the physical condition of the subject. The Mercury is perfectly suitable as a fitness check for fitness clubs or for athletes at schools for example. On the basis of this result a Fitness-Index is calculated with the help of a complex formula taking age, height, weight, test duration and Heart-Rate into consideration, which tells us whether the physical condition of the subject is above or below average. The value of 100 as the average serves as the base. If somebody's index-value is 90 then his physical condition is slightly below average. An index-value of 110 on the other hand would be above average.