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 (VO2 max), we measured peak upright cycle ergometry cardiac volumes (99mTc ventriculography) and plasma (125I-labeled albumin) and red cell (NaCr51) volumes in 7 endurance-trained and 12 age-matched lean sedentary men. The athletes had approximately 40% higher VO2 max 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/m2, P < 0.05) and 17% larger end-diastolic volume indexes. In the total group, VO2 max 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 VO2 max 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 VO2 max in master athletes by eliciting both chronic volume overload and increased utilization of the Frank-Starling effect during exercise.