The goal of the present study was the analysis of the effects of two endurance training interventions (HIIT versus POL) over a period of 5 weeks on 16/17 year old sport major students. The study was integrated in regular P.E. lessons. In addition to the training load, daily changes of easily measurable cardiologic parameters were monitored in order to assess their validity in predicting endurance performance. The students conducted 12 training sessions in two groups. With pre- and post-tests the endurance capacity was determined via Luc Léger’s shuttle run test.