ENHANCED LEFT-VENTRICULAR PERFORMANCE IN ENDURANCE-TRAINED OLDER MEN

Background The age-associated decline in aerobic exercise capacity is partially reversible by endurance exercise training. Moderate-intensit y endurance exercise training increases aerobic exercise capacity medi ated, in part, by improvement of strobe volume and left ventricular pe rformance in older men. The present study was designed to characterize the nature of cardiovascular adaptations to strenuous endurance exerc ise of long duration and to delineate the mechanisms underlying increa sed stroke volume and cardiac output in highly trained older endurance athletes. Methods and Results Nine male master athletes (MA: 64+/-2 y ears old, mean+/-SEM) and 9 older sedentary healthy men (controls: 63/-1 year) were studied. Left ventricular systolic function was evaluat ed with the use of cardiac blood pool imaging and echocardiography. Ma ximal O-2 uptake (Vo(2max)) was 50.4+/-1.7 ml.kg(-1).min(-1) in the MA and 29.6+/-1.4 ml.kg(-1).min(-1) (P=.0001) in controls. Systolic and mean blood pressures at rest and during exercise were not different in the two groups. Left ventricular systolic function at peak exercise w as higher in the MA than in sedentary controls as evidenced by (1) a h igher left ventricular functional reserve (Delta EF: 12.4+/-2 versus 5 .6+/-2.5, P=.05), (2) a large decrease in end-systolic volume during e xercise (MA: 56+/-4 mL at rest and 42+/-5 mL at peak exercise, P=.007; controls: 43+/-2 mL at rest and 42+/-6 mL at peak exercise, P=.35) wi th no differences in systolic blood pressure, (3) a higher left ventri cular fractional shortening at peak exercise (MA: 52+/-2.6%; controls: 45+/-1%, P=.046) at comparable values for end-systolic wall stress (M A: 56+/-12 g/cm(2); controls: 53+/-7 g/cm(2), P=.50), and (4) a greate r decrease in end-systolic diameter at peak exercise in the MA than in controls (MA: -1.2+/-0.16 cm versus -0.57+/-0.13 cm, P=.014) despite no significant differences between the changes in end-systolic wall st ress during exercise (MA: -15.5+/-7.5 g/cm(2), controls: -11.0+/-9.0 g /cm(2), P=.6). MA had a larger end-diastolic volume at rest (153+/-6 v ersus 132+/-4 mL, P=.009) with a normal wall thickness-to-radius ratio (0.34+/-0.02). Peak exercise stroke volume was higher (P=.023) in the MA (132+/-6 mL/min) than in the sedentary controls (111+/-6 mL/min). Changes in stroke volume correlated strongly with changes in ejection fraction in the MA (r=.80, P=.010) but not in sedentary controls (r=.5 9, P=.097). Further, changes in stroke volume from rest to exercise co rrelated strongly with changes in end-diastolic volume in both MA (r=. 78, P=.013) and sedentary controls (r=.73, P=.026), suggestive of reli ance of stroke volume on end-diastolic volume and preload. However, fo r a given increase in end-diastolic volume, the rise in stroke volume during exercise was significantly larger in the MA than in controls, w hich, in the absence of differences in mean blood pressures, indicates that enhanced left ventricular systolic function independent of prelo ad plays an additional role in maintaining a higher stroke volume at p eak exercise in the highly trained older men. Conclusions Cardiac adap tations in older endurance trained men are characterized by volume-ove rload left ventricular hypertrophy and enhancement of left ventricular systolic performance at peak exercise. These adaptive responses contr ibute to enhanced stroke volume at peak exercise in older endurance tr ained men.