In a double-blind placebo controlled study, 14 male healthy volunteers were examined the morning after they had received an evening dose of 20 mg temazepam (Planum) with regard to functional capacity, cardial, cardiovascular and respiratory regulation as well as neuromuscular excitability and metabolic changes. After being exposed to the bicycle ergometer load, oxygen uptake, carbon dioxide output, glucose and lactate concentration were determined; furthermore the neuromuscular excitability of the musculus vastus medialis, musculus rectus femoris and musculus quadrizeps femoris was estimated. Despite unimportant capacity reductions (p greater than 0.05) concerning the maximum capacity (2.2%) as well as the maximum oxygen uptake (4.3%) under treatment with temazepam, there could not be proved any significant changes regarding cardiopulmonary and metabolic functions. On eastern and western flights, top athletes showed a very fast adaptation to the day-night rhythm without hang-over.