Exercise training-induced alterations of cardiac morphology.

The data to date are ambivalent regarding exercise-induced cardiac enlargement in previously sedentary individuals. The training regimens used in previous longitudinal studies probably did not provide an optimum training stimulus. Accordingly we studied echocardiograms of the left ventricle of 11 relatively inactive individuals pre and post an intense endurance training program, when intensity was increased relative to improvement, thereby providing an optimum training stimulus. Subjects trained 6 days/wk for 7 wk, alternating days of continuous cycling (40 min) and interval running (5 5-min bouts). Exercise intensity was maintained at 85-90% of peak cycle ergometer O2 uptake (VO2) for cycle training by increasing power output approximately 11 W/wk and at approximately 100% of VO2max for run training by increased (P less than 0.01) approximately 950 ml/min (approximately 32%) and was correlated with training duration (r = 0.91; P less than 0.01). Training-induced increases (P less than 0.05) in interventricular septal thickness (IVS, mm) during both systole (13.4 +/- 0.9 to 14.9 +/- 0.8) and diastole (10.4 +/- 0.6 to 11.5 +/- 0.7) and in left ventricular end-diastolic dimension (4.96 +/- 0.16 to 5.13 +/- 0.19 cm). The absolute values of left ventricular end diastolic volume (LVEDV), stroke volume, ejection fraction, and left ventricular mass (LVM) increased (P less than 0.05) after training. Increases (P less than 0.05) in LVEDV index (64.3 +/- 3.3 to 69.0 +/- 3.4 ml/m2) and LVM index (114.1 +/- 6.5 to 124.5 +/- 7.3 g/m2) were also evident.(ABSTRACT TRUNCATED AT 250 WORDS)