Unterschiedliche kardiale und metabolische Isoproterenoleffekte in Abhängigkeit vom Trainingszustand

Summary

Six marathon runners (T; VO₂max 65.7±2.0 ml/kg·min) and 6 sports students (S; VO₂max 54.0±2.6 ml/kg·min) were investigated during training specific exercise (graded treadmill ergometric test; TE), non-training specific exercise (graded bicycle ergometric test supine, BE), and following isoproterenol stimulation (2 and 4 µg/min). DuringTE, dopamine (DA), noradrenaline (NA), adrenaline (A), lactate, heart rate, and oxygen uptake were determined. Measurements of DA, NA, A, lactate, heart rate, stroke volume (two dimensions echocardiographic system), and cardiac output were made duringBE. During isoproterenol stimulation, heart rate, stroke volume, cardiac output, as well as glucose, lactate, free fatty acids, and glycerol responses in the blood were measured. NA, A (less significant), lactate, heart rate were significantly lower in T than in S at identical, absolute, submaximal exercise level duringTE. The individuall submaximal NA (r=−0.78), A (r=0.63), lactate (r=0.78), and heart rate responses (r=−0.82) correlated inversely with the VO₂max. DuringBE, these training dependent effects werenot well defined, except for the heart rate (significantly lower in T), and stroke volume (significantly higher in T at the 100 watt level). DA did not show significant training related differences during TE or BE. In the isoproterenol stimulation test, stroke volume, glucose, and free fatty acids levels increase significantly more in T than in S. The individual stroke volume increase correlated with the VO₂max (r=0.75). The results may be indicative at the one hand of a training dependent reduction of sympathetic activity, and on the other hand of a training related increase of sensitivity for sympathetic stimulation.