Plasma catecholamines in trained and untrained volunteers during graduated exercise.

Ten untrained subjects and nine trained cyclists were examined during graduated ergometric exercise in the supine position. The levels of epinephrine and norepinephrine in the blood as well as the heart rate and oxygen intake were determined. At submaximum levels, epinephrine, norepinephrine, lactate, and the heart rate are lower in tthe trained than in the untrained subjects; the relative oxygen intake shows no significant difference. The ergometric work capacity is approximately 30% higher in the trained cyclists. During maximum ergometric exercise, the plasma catecholamines, lactate, and the heart rate show no differences between the two groups; the oxygen intake is approximately 30% higher in the trained than in the untrained subjects. A direct relationship exists between catecholamine levels and lactate; however, this relationship becomes less exact during higher exercise intensities: In reference to the same catecholamine concentration, the lactate levels as well as the submaximum heart rates are higher in the trained than in the untrained subjects, the cause of which could be an increased beta-adrenoceptor sensitivity in the trained subjects.