Exercise testing is an essential part of the annual sports medical check-up for competitive athletes. The aim of the examination is to assess the current health status and to perform medical clearance for competitive sports. In addition, assessment of intraindividual changes over time, interindividual comparisons, and determination of training recommendations are of interest. For the assessment of cardiopulmonary fitness, a bicycle or treadmill ergometry with ECG recordings is usually conducted. The exercise test is performed according to standardized exercise protocols until maximum individual exhaustion. In competitive sports, understanding of the muscular metabolic situation during exercise is crucial for assessing current exercise capacity and for managing workouts. Therefore, exercise tests are often performed as lactate performance testing or cardiopulmonary exercise test. Lactate performance testing is one of the most frequently used methods regarding exercise testing in competitive sports and is a fixed component in most of the annual medical check-ups, which are performed in the sports medicine examination centers of the German Olympic Sports Confederation (DOSB). It enables the analysis of aerobic and anaerobic metabolism during exercise, which allows identification of individual endurance training intensities based on the underlying metabolism. Cardiopulmonary exercise testing is also suitable to determine the maximum oxygen uptake and to better understand medical issues related to exercise capacity.