Arterial and venous plasma catecholamines during submaximal steady-state exercise

Arterial and venous plasma catecholamine responses to 15 min of cycling at 60% of maximal oxygen uptake were examined 11 times during exercise and recovery in nine young men. Intra-arterial blood pressure, heart rate and oxygen uptake were recorded continuously. All variables increased significantly during the initial 4 min, after which oxygen uptake, diastolic blood pressure and arterial plasma adrenaline showed no further increase. Heart rate and plasma noradrenaline, however, continued to increase, although significantly more slowly, and were closely correlated (r = 0.81, 95% CI 0.71-0.87), as were systolic blood pressure and heart rate (r = 0.78, 95% CI 0.71-0.87). Venous plasma adrenaline showed a steady increase during the whole exercise period and thus a different response pattern from arterial plasma adrenaline. In conclusion, arterial plasma catecholamines respond to steady-state exercise by a two-phase pattern paralleling the changes in arterial blood pressure and heart rate. Venous sampling does not reveal this association.