The role of catecholamines, age, and fitness on blood pressure reactivity to dynamic exercise in patients with essential hypertension.

OBJECTIVE

To determine the relationship between exercise blood pressure (BP) and catecholamine levels in hypertensive subjects and, secondarily, to evaluate the influence of age and fitness level.

DESIGN

Descriptive correlational.

SETTING

Midwestern, university-affiliated medical center.

SUBJECTS

27 hypertensive subjects, mean age 45 years, who were free of antihypertensive medications.

OUTCOME MEASURES

BP and plasma catecholamines (norepinephrine and epinephrine).

INTERVENTION

Subjects were given an incremental maximal exercise test on a cycle ergometer beginning at 25 watts with workloads increasing by 25 watts every 2 minutes until exhaustion. Plasma catecholamines were measured at rest, at 100 watts, and at maximal exercise. BP, heart rate, and oxygen consumption (VO2) were measured at rest and at the end of each workload.

RESULTS

Systolic and diastolic BP were unrelated to catecholamines at rest and during exercise. When subjects were evaluated according to fitness level (VO2max), resting BP was not significantly different among groups (low fitness = VO2max < or = 25 ml/kg/min; moderate fitness = VO2max 26 to 39 ml/kg/min; high fitness = VO2max > or = 40 ml/kg/min). However, an inverse relationship was observed between fitness level and rate of rise of systolic and diastolic BP during submaximal work. Multiple regression showed that fitness predicted diastolic BP response (p = 0.02) at 100 watts. Age, however, predicted systolic BP response (p = 0.015).

CONCLUSIONS

Neither the level of resting nor the magnitude of BP response to exercise in hypertensive subjects was directly related to level of plasma catecholamines. The magnitude of change in BP during exercise was modulated by age and fitness level.