Share this article on:

00005768-200705001-0144000005768_2007_39_s168_ogoh_baroreflex_5miscellaneous< 16_0_1_0 >Medicine & Science in Sports & Exercise© 2007 American College of Sports MedicineVolume 39(5) SupplementMay 2007p S168Increases In Central Blood Volume Modulate Carotid Baroreflex Resetting During Dynamic Exercise In Humans: 1259: Board #22 May 30 11:00 AM ‐ 12:30 PM[A-23 Free Communication/Poster – Blood Pressure and Heart Rate Variability: MAY 30, 2007 7:30 AM - 12:30 PM ROOM: Hall E]Ogoh, Shigehiko; Fisher, James P.; Fadel, Paul J.; Raven, Peter B. FACSM1University of North Texas Health Science Center, Fort Worth, TX.2University of Missouri-Columbia, Columbia, MO. Email: sogoh@hsc.unt.edu Supported in part by NIH grant #HL045547, AHA #0465104Y and ACSM Visiting Scholar AwardNumerous studies have indicated that activation of central command or the exercise pressor reflex independently, or in combination, are required for the arterial baroreflex to reset during exercise. Although it has been suggested that increases in central blood volume (CBV) produced by the muscle pumping of leg exercise influences the locus of the operating point of the carotid-vasomotor reflex, limited studies have addressed this possibility.PURPOSE: The present study was designed to test the hypothesis that resetting of the operating point of the carotid-vasomotor baroreflex function curve during exercise is modulated by increases in CBV.METHODS: Changes in subject posture (supine vs. upright) and pedal frequency (80 vs. 60 revolutions per minute (rpm)) were used to increase CBV, while oxygen uptake (VO2) was kept constant. Eight male subjects (29±1 yrs) performed three exercise trials: upright cycling at 60 rpm (Control); supine cycling at 60 rpm (SupEX) and upright cycling at 80 rpm (80EX). During each condition, carotid baroreflex (CBR) function was determined using the rapid neck pressure (NP) and neck suction (NS) protocol.RESULTS: Although mean arterial pressure (MAP) was significantly elevated from rest (88±2 mmHg) during all exercise conditions (P<0.001), the increase in MAP was lower during SupEX (94±2 mmHg) and 80EX (95±2 mmHg) compared with Control (105±2 mmHg, P<0.05). Importantly, the blood pressure responses to NP and NS were maintained around the changed operating points of MAP. However, in comparison to Control, the carotid-vasomotor baroreflex function curve was relocated downward and leftward when CBV was increased during SupEX and 80EX. These alterations in CBR resetting occurred without any differences in VO2 or heart rate between the exercise conditions.CONCLUSIONS: Increasing CBV and loading the cardiopulmonary baroreflex reduces the magnitude of exercise-induced increases in MAP and CBR resetting. These findings suggest that changes in cardiopulmonary baroreceptor input influence CBR resetting during dynamic exercise.Increases In Central Blood Volume Modulate Carotid Baroreflex Resetting During Dynamic Exercise In Humans: 1259: Board #22 May 30 11:00 AM ‐ 12:30 PMOgoh, Shigehiko; Fisher, James P.; Fadel, Paul J.; Raven, Peter B. FACSMA-23 Free Communication/Poster - Blood Pressure and Heart Rate Variability: MAY 30, 2007 7:30 AM - 12:30 PM ROOM: Hall E539