Abstract
To test the influence of aerobic physical training on pressor response to infused
norepinephrine, the present study utilized a single subject A-B-A-B withdrawal design
consisting of 9-week alternating sedentary and aerobic phases (S1, A1, S2, A2). During
each 9-week phase the subject underwent infusions every 3 weeks, consisting of saline,
low-dose and high-dose norepinephrine (Low-NE, High-NE). Heart rate and mean arterial
blood pressure were monitored continuously; resting platelet and plasma catecholamines
were also measured. Infusions were conducted 48 h from the most recent exercise bout
to minimize residual effects of acute exercise. Fitness level was confirmed by V̇O2max during graded exercise testing at the conclusion of each 9-week phase. Blood pressure
during saline did not differ between aerobic and sedentary phases. However, in all
but one comparison, aerobic fitness was associated with a highly significant reduction
in pressor response during Low-NE as well as High-NE. Plasma norepinephrine was higher
during the two aerobic phases; platelet catecholamines and plasma epinephrine showed
no reliable association with fitness. Results for this subject support an attenuation
of pressor response associated with aerobic conditioning.
Key words
Areobic physical training - norepinephrine - mean arterial pressure - pressor response
