Left ventricular function during interval and steady state exercise

Purpose: Interval training (INT) is a commonly used method of exercise trai ning in both athletic and clinical populations. Although we generally under stand left ventricular (LV) function during steady state (SS) exercise, the re are no data regarding LV function during INT. Methods: We studied eight healthy, physically active volunteers during upright cycle ergometry during 15 min of both SS and INT, at the same average power output (90% individua l anaerobic threshold), using first pass radionuclide ventriculography. Dur ing INT (60s/60s), measures of LV function were made during work (220 W) af ter 4 and 12 min and during recovery (120 W) after 7 and 15 min. These were compared with the average of four temporally matched measures made during SS (170 W). Results: During INT, LV ejection fraction increased from rest ( 67 +/- 6%) to 77 +/- 5, 80 +/- 5, 77 +/- 5 and 79 +/- 4% after 4, 7, 12, an d 15 min, respectively. During SS, LV ejection fraction was not significant ly different at rest (70 +/- 4%) or during exercise (76 +/- 4, 79 +/- 4, 80 +/- 3, and 81 +/- 3%) after 4, 7, 12, and 15 min, respectively. Other meas ures of LV function (HR, BP, LV volumes, cardiac output, systemic vascular resistance, peak emptying, and filling rates) were likewise similar during temporally matched measurements during INT and SS. Conclusions: Although th ere were the expected transitions of ejection fraction with work and recove ry, the overall hemodynamic picture during INT was very similar to SS. Thes e data suggest that LV function during INT is not substantially different t o that during SS.