The aim of the research was to establish differences between the HR values and maximal blood lactate concentration assessed during the performance of a step aerobics programme at three different heights of step-bench. The sample consisted of 12 female aerobics instructors, aged between 20 and 28. The subjects executed a pre-defined choreography uninterruptedly for 30 minutes on a step bench, which was set at three different heights: 20, 25 and 30 cm, and to the music set at 135 bpm. At the beginning and immediately after the 30-minute activity HRpeak and blood lactate - bLA concentration were measured. HR monitors, recording data every 5 minutes, controlled the HRpeak. Data processing was performed using SPSS statistical programme, descriptive statistics method and t-test for establishing differences between the subjects’ HR. It was established that there were statistically significant differences between the subjects in terms of average HR at various step bench heights. It was also established that the lactate values did not rise proportionately to the HR values.