Enhanced vagal baroreflex response during 24 h after acute exercise.
We evaluated carotid-cardiac baroreflex responses in eight normotensive men (25-41 yr) on two different test days, each separated by at least 1 wk. On one day, baroreflex response was tested before and at 3, 6, 12, 18, and 24 h after graded supine cycle exercise to volitional exhaustion. On another day, this 24-h protocol was repeated with no exercise (control). Beat-to-beat R-R intervals were measured during external application of graded pressures to the carotid sinuses from 40 to -65 mmHg; changes of R-R intervals were plotted against carotid pressure (systolic pressure minus neck chamber pressure). The maximum slope of the response relationship increased (P less than 0.05) from preexercise to 12 h (3.7 +/- 0.4 to 7.1 +/- 0.7 ms/mmHg) and remained significantly elevated through 24 h. The range of the R-R response was also increased from 217 +/- 24 to 274 +/- 32 ms (P less than 0.05). No significant differences were observed during the control 24-h period. An acute bout of graded exercise designed to elicit exhaustion increases the sensitivity and range of the carotid-cardiac baroreflex response for 24 h and enhances its capacity to buffer against hypotension by increasing heart rate. These results may represent an underlying mechanism that contributes to blood pressure stability after intense exercise.
Convertino
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VA
Life Sciences Research Office, National Aeronautics and Space Administration, Kennedy Space Center, Florida 32899.
Adams
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WC
D000328:Adult; D001794:Blood Pressure; D002346:Carotid Sinus / Q000502:physiology; D015444:Exercise; D006801:Humans; D008297:Male; D011311:Pressoreceptors / Q000502:physiology*; D011312:Pressure; D012018:Reflex / Q000502:physiology*; D013997:Time Factors; D014630:Vagus Nerve / Q000502:physiology*