Comparism of the article on endogeneous opiates, Runner's High and exercise addiction - The rise and decline of a myth Summary: The here discussed problems show, that physiological explanation theories for an improved mood after exercise does not fit any longer. Especially the endorphin theory is covered with too much problems. In summary, we can conclude - that if endorphin works - it works only for the ghighly trainied individuals. But you can find ß-End IRM elevations in highly trained and less trained athletes. At least you need to exercise half an hour or longer. We only have very few studies using a longitudinal design. Post- Race values only can tell you something about a post-race-state. Furthermore the most studies are ignoring the circadian rythmic of the hormone secretion and the female menstrual cycle. All studies are ignoring basic pharmacological refelctions about Cross-reactivity, Receptor Up- and Down-Regulation, Receptorfields in the brain and the blood-brain barrier. Latest results from experimental studies also show, that groups with an exercise intervention have the same mood-effects sa groups with a non-exercsie-intervention (and so no ndorphn-secretion). All these aspects leads us to tzhe conclsuion that the endorphin theory must be a myth.