Analysis of alteration of blood pressure response to exercise through baroreflex

The baroreflex has been reported to play an important role in hemodynamic regulation during exercise. Therefore, impairment of baroreflex function can induce an abnormal response of systolic blood pressure (SBP) to exercise, including exercise-induced hypertension. To clarify whether baroreflex function alters SBP response, we examined the relationship of baroreflex sensitivity (BRS) with SBP response to exercise.

In 22 subjects without cardiac dysfunction, BRS (ms/mmHg) was measured by the phenylephrine method, and a treadmill exercise test was administered according to Bruce's protocol.

1) The chronotropic response to exercise was higher in the normal BRS group than in the reduced BRS group (p<0.01). The SBP at the initial phase of exercise (1 min after the start of exercise) showed a smaller increase in the normal BRS group than in the reduced BRS group (p<0.01). During the initial phase of exercise, BRS had negative correlation with the SBP increment from rest (r=-0.408, p<0.05). During submaximal exercise (6 min after the start of exercise), a positive correlation between BRS and SBP response (r=0.422, p<0.05) was shown. 2) Subjects were divided into 2 groups: 12 subjects with normal BRS (> or =5 ms/mmHg) and 10 subjects with reduced BRS (<5 ms/mmHg). During the initial exercise phase, the negative correlation between BRS and SBP response was stronger in the normal BRS group (r=-0.398) than in the reduced BRS group (r= -0.126). During submaximal exercise, BRS had a positive correlation with BP response to exercise in subjects with normal BRS (r=0.462).

Preserved baroreflex function is thought to be related to the pressor response to submaximal exercise, although the baroreflex is thought to be associated with the stabilization of blood pressure change during the initial exercise phase. These findings suggest that exercise-induced hypertension develops through the baroreflex mechanism.