TY - JOUR
T1 - Cardiovascular function following reduced aerobic activity
AU - Raven, Peter B.
AU - Welch-O'Connor, Rita M.
AU - Shi, Xiangrong
PY - 1998/7
Y1 - 1998/7
N2 - Purpose: The aim of this study was to test the hypothesis that a sustained reduction of physical activity (deconditioning) would alter the cardiovascular regulatory function. Methods: Nineteen young, healthy volunteers participated in physical deconditioning for a period of 8 wk. Before (pre) and following (post) physical deconditioning, the responses of heart rate (HR), mean arterial pressure (MAP, measured by Finapres), central venous pressure (CVP), stroke volume (SV, Doppler), and forearm blood flow (FBF, plethysmography) were determined during lower body negative pressure (LBNP). The carotid baroreflex (CBR) function was assessed using a train of pulsatile neck pressure (NP) and suction, and the aortic baroreflex control of HR was assessed during steady-state phenylephrine (PE) infusion superimposed by LBNP and NP to counteract the PE increased CVP and carotid sinus pressure, respectively. Results: Active physical deconditioning significantly decreased maximal oxygen uptake (-7%) and LBNP tolerance (- 13%) without a change in baseline hemodynamics. Plasma volume (-3% at P = 0.135), determined by Evans Blue dilution, and blood volume (-4% at P = 0.107) were not significantly altered. During LBNP -20 to -50 torr, there was a significantly greater drop of SV per unit decrease in CVP in the post- (14.7 ± 1.6%/mm Hg) than predeconditioning (11.2 ± 0.7%/mm Hg) test accompanied by a greater tachycardia. Deconditioning increased the aortic baroreflex sensitivity (pre vs post: -0.61 ± 0.12 vs -0.84 ± 0.14 bpm·mm- 1 Hg, P = 0.009) and the slope of forearm vascular resistance (calculated from [MAP-CVP]/FBF) to CVP (-2.75 ± 0.26 vs -4.94 ± 0.97 PRU/mm Hg, P = 0.086). However, neither the CBR-HR (-0.28 ± 0.03 vs -0.39 ± 0.10 bpm·mm- 1 Hg) nor the CBR-MAP (-0.37 ± 0.16 vs -0.25 ± 0.07 mm Hg/mm Hg) gains were statistically different between pre- and postdeconditioning. Conclusions: We concluded that the functional modification of the cardiac pressure-volume relationship resulted in the reduced LBNP tolerance, despite the accentuated aortic and cardiopulmonary baroreflex function following deconditioning.
AB - Purpose: The aim of this study was to test the hypothesis that a sustained reduction of physical activity (deconditioning) would alter the cardiovascular regulatory function. Methods: Nineteen young, healthy volunteers participated in physical deconditioning for a period of 8 wk. Before (pre) and following (post) physical deconditioning, the responses of heart rate (HR), mean arterial pressure (MAP, measured by Finapres), central venous pressure (CVP), stroke volume (SV, Doppler), and forearm blood flow (FBF, plethysmography) were determined during lower body negative pressure (LBNP). The carotid baroreflex (CBR) function was assessed using a train of pulsatile neck pressure (NP) and suction, and the aortic baroreflex control of HR was assessed during steady-state phenylephrine (PE) infusion superimposed by LBNP and NP to counteract the PE increased CVP and carotid sinus pressure, respectively. Results: Active physical deconditioning significantly decreased maximal oxygen uptake (-7%) and LBNP tolerance (- 13%) without a change in baseline hemodynamics. Plasma volume (-3% at P = 0.135), determined by Evans Blue dilution, and blood volume (-4% at P = 0.107) were not significantly altered. During LBNP -20 to -50 torr, there was a significantly greater drop of SV per unit decrease in CVP in the post- (14.7 ± 1.6%/mm Hg) than predeconditioning (11.2 ± 0.7%/mm Hg) test accompanied by a greater tachycardia. Deconditioning increased the aortic baroreflex sensitivity (pre vs post: -0.61 ± 0.12 vs -0.84 ± 0.14 bpm·mm- 1 Hg, P = 0.009) and the slope of forearm vascular resistance (calculated from [MAP-CVP]/FBF) to CVP (-2.75 ± 0.26 vs -4.94 ± 0.97 PRU/mm Hg, P = 0.086). However, neither the CBR-HR (-0.28 ± 0.03 vs -0.39 ± 0.10 bpm·mm- 1 Hg) nor the CBR-MAP (-0.37 ± 0.16 vs -0.25 ± 0.07 mm Hg/mm Hg) gains were statistically different between pre- and postdeconditioning. Conclusions: We concluded that the functional modification of the cardiac pressure-volume relationship resulted in the reduced LBNP tolerance, despite the accentuated aortic and cardiopulmonary baroreflex function following deconditioning.
KW - Baroreflex
KW - Blood volume
KW - Central venous pressure
KW - Deconditioning
KW - Forearm blood flow
KW - Orthostatic tolerance
KW - Stroke volume
KW - Tachycardia
UR - http://www.scopus.com/inward/record.url?scp=0031818008&partnerID=8YFLogxK
U2 - 10.1097/00005768-199807000-00004
DO - 10.1097/00005768-199807000-00004
M3 - Article
C2 - 9662671
AN - SCOPUS:0031818008
SN - 0195-9131
VL - 30
SP - 1041
EP - 1052
JO - Medicine and Science in Sports and Exercise
JF - Medicine and Science in Sports and Exercise
IS - 7
ER -