To determine the effect of plasma volume change with short-term training and diuresis on left ventricular diastolic filling and exercise oxygen uptake (VO2) in older versus younger men.
Eleven older (68 ± 5 y) physically active (maximal oxygen uptake [VO2max] = 25.9 ± 3.6 mL · kg−1 · min−1) and 10 younger sedentary males (24 ± 5 y, VO2max 40.5 ± 5.0 mL · kg−1 · min−1) were randomly assigned to 5 consecutive days of (1) 1 h/d high intensity stationary cycling (EXER); (2) 100 mg/d spironolactone (DIUR); and (3) exercise and diuretic (EXDI). Each treatment was separated by a 21-day washout. Doppler echocardiographic indices of left ventricular diastolic filling including peak early and atrial transmitral flow velocity and isovolumic relaxation time; percent change in plasma volume; submaximal VO2 kinetics; and VO2max were determined at baseline and 48 hours after each treatment.
Plasma volume was increased more in the young following EXER (8.92 ± 7.6 vs. 6.2%, P = 0.038) and decreased more in the older group following DIUR (−11.5% vs. −3.54 ± 9.0, P < 0.001). There was no significant difference between groups after EXDI. Significant changes in peak early flow velocity with EXER in older subjects were not reflected in any other changes in left ventricular diastolic filling across conditions. No changes in left ventricular diastolic filling were observed in the young group with any condition. VO2max and VO2 kinetics were unchanged under all conditions from baseline in both groups.
These results suggest that exercise VO2 responses either at maximal or submaximal workrates are not limited by alterations in left ventricular pump function in physically fit older adults.
Departments of Family Medicine,* Physical Medicine, and Rehabilitation† and Physiology,‡ Faculty of Medicine, Schools of Kinesiology§ and Physical Therapy,∥ Faculty of Health Sciences, University of Western Ontario, London, Canada
Received for publication December 2002; accepted March 2003.
Reprints: Robert J. Petrella, Heart Health and Exercise Laboratory, Centre for Activity and Ageing, 1490 Richmond St., London, Ontario, Canada N6G 2M3. E-mail: firstname.lastname@example.org