Cardiac performance in endurance-trained and moderately active young women

To compare the cardiac performance of endurance-trained (ET) and moderately active (MA) young women before exercise and throughout incremental work rates to maximum with particular interest in whether their stroke volume (SV) levels off at a submaximal work rate or increases to maximum.

Blood volume (BV), and exercise cardiac performance were examined in seven ET (VO2max = 64.3 +/- 2.0 mL.kg(-1).min(-1)) and seven MA (VO2max = 42.1 +/- 1.0 mL.kg(-1).min(-1)) women, aged 18-30 yr. Cardiac time intervals were measured at matched heart rates (HR).

ET had a significantly larger BV than MA in both mL (ET = 5053 +/- 139, MA = 4327 +/- 202) and mL.kg(-1) (ET = 83.1 +/- 1.4, MA = 72.9 +/- 2.7). The SV of ET was significantly larger than the SV of MA throughout exercise, and the SV of ET increased progressively throughout incremental work rates to maximum. Although the SV of MA initially leveled off at a submaximal work rate, it underwent a secondary increase at very heavy work rates. Both diastolic filling rate (DFR) and left ventricular emptying rate (LVER) were significantly faster in ET compared with MA at HR of 150 bpm, 170 bpm and HRmax, and in both ET and MA, DFR was significantly faster than LVER at 170 bpm and HRmax.

In young women, ET have a larger SV than MA due to an enhanced DFR and LVER, with the primary advantage being DFR (possibly due to their larger BV). In addition, the SV of ET increases progressively throughout incremental work rates to maximum with no plateau, whereas the SV of MA levels off through moderate to heavy work rates then undergoes a secondary increase at very heavy work rates.