This study aimed to investigate the relationship between the ability to perceive an Exertion quantified through BORG-Scale (6-20) and endurance level. Therefore 16 females and 28 males completed a lactate performance diagnostic as well as a 5000 meter course. Subjective Perception of effort was quantified according to BORG Scale (6-20). Participants were sex-divided and grouped in well endurance trained participants and not endurance trained participants. The analysis showed no clear differences between the two groups. Generally, lactate showed a closer correlative relationship with subjective perceived exertion than heart rate.