The aim of this diploma thesis was to investigate the physiological acute reactions of a sports student to continuous and high intensity interval training. These reactions were compared at the same middle load. The interval method used was based on (a method known in the literature as the ?norwegian method?) 4x4? 90-95% HRmax and was executed with active and passive recovery. After the Conconi test, the middle loads were determined above VT1 and under VT2. In comparison to the continuous exercise, all endurance interval trainings have shown an increase of oxygen uptake. The variability (difference) between the VO2 at continuous and VO2 at interval training turned out to be less at the higher middle load. Interestingly one interval training could be accomplished with nearly 97%HRmax, which can be explained by the favourable deflection of the heart rate performance curve. The results suggest, that the interval training method is- in contrast to the continuous exercise with the same middle load- a more effective form of training, in reference to the maximum oxygen uptake and lactate tolerance.