Abstract
Introduction. `Sleep high - training low' (SHTL) has reportedly an effect to improve physical performance and this effect is assumed to be increase of oxygen delivery. However, the cardiac function which may contribute to oxygen delivery, has not been studied. This study was designed to investigate the effect of SHTL on cardiac functions. Methods. 21 healthy well-trained thiathlon athletes, aged 21±5 yrs, were divided into SHTL- and SL-group (11 and 10, respectively). Performing the same training program at sea level for 2 weeks, the subjects of SL-group lived at sea level, while those of SHTL-group stayed at an altitude of 1950m (>12h/day). Doppler echocardiography was performed at rest at sea level before and immediately after the training program. Results. The diameters of left atrium, aortic root and end-diastolic left ventricle did not change after the training program, and there was no significant difference between both groups. After the training the left ventricular end-systolic diameter of SHTL-group decreased by 10.6%(P<0.05) while that of SL-group did not change. In SHTL-group shortening fraction and ejection fraction increased from 33.5% to 38.5% and 61.9% to 75.9%, respectively, and the ratio of pre-ejection period to left ventricular ejection time was reduced by 18.2% (P<0.01), while those of SL-group did not change significantly. The peak flow velocity of early filling (E) and late filling (A) as well as E/A did not change significantly, no difference between both groups. Conclusion. Two-week SHTL did not clearly affect the diastolic functions but improved systolic functions significantly, which probably as a result from an improved ventricular contractibility.
Published Version
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