Cardiac output and stroke volume changes with endurance training: The HERITAGE Family Study

Purpose: The purpose of this study was to determine the magnitude of change s in cardiac output (Qc), stroke volume (SV), and arterial-mixed venous oxy gen difference (a-(v) over barO(2) diff) during submaximal exercise followi ng a 20-wk endurance training pro,sram, with the primary focus on identifyi ng differences in response by race, sex, and age. Methods: The participants in this study (N = 631) were healthy and previously sedentary men (N = 277 ) and women (N = 354) of varying age (17-65 yr) and race (blacks, N = 217; whites, N = 414) who had completed the HERITAGE Family Study protocol. Afte r baseline measurements, participants trained on cycle ergometers 3 d.wk(-1 ) for a total of 60 exercise sessions starting at the HR associated with 55 % of maximal oxygen uptake ((V) over dot O-2max) for 30 min/session and bui lding to the HR associated with 75% of (V) over dot O-2max for 50 min/sessi on, which was maintained during the last 6 wk. HR, Qc (CO2 rebreathing), an d SV (Qc/HR) were determined in duplicate at 50 W and at 60% of (V) over do t O-2max on two different days both before and after training. Results: Aft er training, there were significant decreases in HR and Qc, and significant increases in SV and a-(v) over barO(2) diff at 50 W (except for no change in a-(v) over barO(2) diff in black men). The changes in HR differed by sex and age, and the changes in SV, Qc, and a-(v) over barO(2) diff differed b y race. Qc decreased by 0.6 L.min(-1) at 50 W for the total sample, consist ent with the decrease in (V) over dot O-2 at this power output. At 60% of ( V) over dot O-2max, HR decreased, and SV, Q, and a-(v) over barO(2) diff in creased. There were small differences in response by sex (HR and SV), race (KR), and age (HR and Qc). Conclusion: It is concluded that the cardiovascu lar systems of men and women, blacks and whites, and younger and older subj ects are not limited in their ability to adapt to endurance training.