Quantifying actual individual training intensity in resistance training is essential for athletes and trainers, but is at present only possible with methodological problems. Thus, the purpose of this article is to examine the relationship of different types of RPE (rating of perceived exertion) with blood lactate concentrations in hypertrophy training. Hereby it is possible, to deduce conclusions about the validity of the RPE-scale and different times of monitoring. In this article two studies with male subjects are presented (study 1: n=10, 23.7 ± 2.8 years; study 2: n=16, 24.9 ± 2.0 years). In both surveys, subjects had to complete 3 sets with 3 minutes of rest between sets in every exercise. Blood lactate was measured before each exercise and two minutes after the completion of each set.