Does fitness level modulate the cardiovascular hemodynamic response to exercise?
Subjects with greater aerobic fitness demonstrate better diastolic compliance at rest, but whether fitness modulates exercise cardiac compliance and cardiac filling pressures remains to be determined. On the basis of maximal oxygen consumption (VO2max), healthy male subjects were categorized into either low (LO: VO2max=43+/-6 ml.kg-1.min-1; n=3) or high (HI: VO2max=60+/-3 ml.kg-1.min-1; n=5) aerobic power. Subjects performed incremental cycle exercise to 90% Vo(2max). Right atrial (RAP) and pulmonary artery wedge (PAWP) pressures were measured, and left ventricular (LV) transmural filling pressure (TMFP=PAWP-RAP) was calculated. Cardiac output (CO) and stroke volume (SV) were determined by direct Fick, and LV end-diastolic volume (EDV) was estimated from echocardiographic fractional area change and Fick SV. There were no between-group differences for any measure at rest. At a submaximal workload of 150 W, PAWP and TMFP were higher (P<0.05) in LO compared with HI (12 vs. 8 mmHg, and 9 vs. 4 mmHg, respectively). At peak exercise, CO, SV, and EDV were lower in LO (P<0.05). RAP was not different at peak exercise, but PAWP (23 vs. 15 mmHg) and TMFP (12 vs. 6 mmHg) were higher in LO (P<0.05). Compared with less fit subjects, subjects with greater aerobic fitness demonstrated lower LV filling pressures during exercise, whereas SV and EDV were either similar (submaximal exercise) or higher (peak exercise), suggesting superior diastolic function and compliance.
Faculty of Physiucal Education and Recreation, University of Alberta, Edmonton, Canada. stickland@wisc.edu
Michael K
MK
Stickland
Robert C
RC
Welsh
Stewart R
SR
Petersen
John V
JV
Tyberg
William D
WD
Anderson
Richard L
RL
Jones
Dylan A
DA
Taylor
Marcel
M
Bouffard
Mark J
MJ
Haykowsky
D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D004452:Echocardiography; D015444:Exercise / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology; D016276:Ventricular Function