Inclusion Criteria:  Female or male aged 18-50 years Proof of physical fitness (e.g. sports medical examination required) for measurements with higher intensities (e.g. endurance tests, competition simulation) Competition experience at the national or international level in an endurance sport VO2max ≥50ml/kg/min for females; ≥55 ml/kg/min for males  Exclusion Criteria:  Systemic disease or other known pathology in the organs: heart, lungs, kidney, stomach, spleen, liver, gall bladder, and intestines. Evidence of pulmonary disease: forced expiratory volume in one second/forced expiratory volume < 70% with/without symptoms (cough, sputum) or other evidence of pulmonologic disease. Diabetes II. Neurological or psychological disease of any kind. Currently undergoing medical or psycho-therapeutic treatment. Health condition that does not allow regular participation in the training forms (e.g. acute illnesses such as fever or other flu-like infections within the last 7 days before the start of the study), orthopedic diseases, injuries to the muscular, bone, joint or tendon apparatus within the last three months. Alcohol or drug abuse. Already high training volume with high intensity training (more than 2 weekly training sessions of high-intensity training)