Norepinephrine response to exercise at the same relative intensity before and after endurance exercise training

It is well documented that endurance exercise training results in a blunted norepinephrine (NE) response to exercise of a given absolute exercise inte nsity. However, it is not clear what effect training has on the catecholami ne response to exercise of the same relative intensity because previous stu dies have provided conflicting results. The purpose of the present study wa s, therefore, to determine the catecholamine response to exercise of the sa me relative exercise intensity before and after endurance exercise training . Six women and three men [age 28 +/- 8 (SD) yr] performed 10 wk of trainin g. Maximal O-2 uptake (V)overdoto(2max) was determined during treadmill exe rcise. Fifteen-minute treadmill exercise bouts were performed at 60, 65, 70 , 75, 80, and 85% of (V)overdoto(2max) before and after training. (V)overdo to(2max) was increased by 20% (from 39.2 +/- 7.7 to 46.9 +/- 8.1 ml.kg(-1). min(-1); P < 0.05) in response to training. Plasma NE concentrations were higher (P < 0.05) during exercise at the same relative intensity after, com pared with before, training at 65-85% of (V)overdoto(2max). Differences bet ween heart rates and plasma epinephrine concentrations after, compared with before, training were not statistically significant. These results provide evidence that the NE response to exercise is dependent on the absolute as well as the relative intensity of the exercise.