Relationship between maximal oxygen uptake and left ventricular function in exercise

Left ventricular systolic time intervals (STI's), cardiac output, and arterial blood pressures were measured during bicycle ergometer work in three groups of 10 young men (aged 20–33 yr) who represented average (VO2max = 42–45 ml.kg-1.min-1), moderate (VO2max = 50–56 ml.kg-1.min-1), and high (VO2max = 59–72 ml.kg-1.min-1) levels of cardiovascular fitness. The subjects were studied using noninvasive procedures at steady-state heart rate of approximately 110, 130, and 150 beats.min-1. At all exercise levels, the fitter subjects displayed slightly shorter values for the preejection period (PEP) compared with less fit groups. Significantly (P less than 0.05) larger stroke volumes, longer left ventricular ejection times (LVET), faster mean systolic ejection rates and lower PEP/LVET ratios were found in the group with the highest aerobic capacity. Although these observations appear to indicate a superior mean level of left ventricular performance in groups who represent high levels of cardiovascular fitness, it was concluded that the use of STI values by themselves to describe the cardiovascular fitness of an individual would not be warranted.