[Plasma dopamine, noradrenaline and adrenaline response during cardiac and peripheral-muscular exhaustion]

Nine healthy subjects performed 2 different graded bicycle ergometric tests. The 1st test started with 50 watt and was increased 50 watt after 3 min till exhaustion as a model of a metabolic and cardiac exhaustion. The 2nd test started with 100 watt and was increased 50 watt after 15 min till exhaustion as a model of a peripheral-muscular exhaustion. The behaviour of plasma catecholamines, lactate and glucose levels, heart rate and oxygen intake was examined. The results were as following: Performance ability 305 (test 1) and 233 watt (test 2; mean values), work time 17.5 min (1) and 51 min (2), heart rate 185 min-1 (1) and 175 min-1 (2), noradrenaline 30.7 nmol/l (1) and 11.0 nmol/l (2), adrenaline 6.9 nmol/l (1) and 2 nmol/l (2), lactate 9.2 (1) and 6.6 mmol/l (2), glucose 5.6 mmol/l (1) and 4.7 mmol/l (2). During highly intensive dynamic exercise (test 1), three times higher catecholamine and 50% higher lactate responses were observed, than during peripheral-muscular limited endurance exercise (test 2). Above an exercise level of more than 30% VO2 max., nor- and adrenaline increased significantly. Below 50-70% VO2 max. steady-state-behaviour occurred. Above this range unsteady-state-behaviour of plasma catecholamines was observed. Dopamine did not show any significant time and intensity dependent increase. Noradrenaline and adrenaline followed the same initial 1st order elimination kinetic.