Expanded blood volumes contribute to the increased cardiovascular performance of endurance-trained older men

To determine whether expanded intravascular volumes contribute to the older athlete's higher exercise stroke volume and maximal oxygen consumption ((V) over dot O-2max), we measured peak upright cycle ergometry cardiac volumes (Tc-99m ventriculography) and plasma (I-125-labeled albumin) and red cell (NaCr51) volumes in 7 endurance-trained and 12 age-matched lean sedentary men. The athletes had similar to 40% higher (V) over dot O-2max values than did the sedentary men and larger relative plasma (46 vs. 38 ml/kg), red cell (30 vs. 26 ml/kg), and total blood volumes (76 vs. 64 ml/kg) (all P < 0.05). Athletes had larger peak cycle ergometer exercise stroke volume indexes (75 vs. 57 ml/m(2), P < 0.05) and 17% larger end-diastolic volume indexes. In the total group, (V) over dot O-2max, correlated with plasma, red cell, and total blood volumes (r = 0.61-0.70, P < 0.01). Peak exercise stroke volume was correlated directly with the blood volume variables (r = 0.59-0.67, P < 0.01). Multiple regression analyses showed that fat-free mass and plasma or total blood volume, but not red cell volume, were independent determinants of (V) over dot O-2max, and peak exercise stroke volume. Plasma and total blood volumes correlated with the stroke volume and end-diastolic volume changes from rest to peak exercise. This suggests that expanded intravascular volumes, particularly plasma and total blood volumes, contribute to the higher peak exercise left ventricular end-diastolic volume, stroke volume, and cardiac output and hence the higher (V) over dot O-2max in master athletes by eliciting both chronic volume overload and increased utilization of the Frank-Starling effect during exercise.