Relationships between catecholamines in urine and physical and mental effort.

Excretion of noradrenaline and adrenaline was investigated in two experiments which included 3 physical test sessions and 3 mental test sessions (Experiment X) and a week of real-life situations (Experiment Y). An increased excretion of both catecholamines was found during each test in Experiment X. The noradrenaline excretion discriminated well between physical and mental tests, but one i.e. 35% VO2max. Adrenaline excretion discriminated the arithmetic test (AT) from the other mental tests. The noradrenaline/adrenaline ratio (NA/A) separated the AT from all other tests. The different adrenergic response patterns to physical and mental effort were confirmed in the real-life situations. The NA/A ratio reflected these differences. It was over 5 for physical activities and between 2 and 3 for mental activities. The different response patterns allow one to differentiate between physical and mental effort.