Conflicting theories discuss whether or not endurance training improves heart contractility, even though most studies have found no changes (Pluim et al., 1999) Traditionally, echocardiography has been used to show ejection fraction (EF) and fractional shortening (FS) to reflect myocardial contractility. However, the sensitivity of EF and FS has been debated, using the argument that these methods only provide indirect measurements of contractility, due to the influence of hemodynamic conditions. Tissue Velocity Imaging (TVI) has been developed in order to provide a more direct measurement of contractility. Based on measuring longitudinal myocardial systolic velocities (PSV), TVI has been found to reflect contractility better than EF (Bach 1996) and also provides analyses during exercise. As TVI has been found a more sensitive method for measuring contractility, this study attempts to investigate whether TVI can prove the Hypothesis that endurance trained athletes (ETA) have enhanced myocardial contractility, at rest and during exercise. Methods: Ten elite male cross-country skiers and ten untrained subjects (US) (mean; age: 28 respectively 28 yr; body height: 180 resp.181 cm; body mass: 76 resp. 70 kg; VO2max: 72 resp. 46 ml kg-1 min-1) performed a progressive combined arm and leg (ratio 25:75) upright sitting cycle work to exhaustion. The protocol was designed to provide registrations at every 10% level from 50 to 100% of VO2max with continued work. In the last 30 s of each 3 min step, measurements were taking using echocardiography (GE vivid7 Pro; Horten, Norway), sphygmomanometer (TriCUFF WA DS55, AJ Medical, Stockholm, Sverige) and oxygen uptake device (Oxycon Pro, Jaeger, Würzburg, Germany). Statistical significance was set to P<0.05. Results: No changes in PSV were found at rest between the two groups (7,6 cm/s vs. 7,4 cm/s). During exercise at 70% to 100% of VO2max ETA had a higher PSV than the US, a difference which increased continuously (from 18% to 36%). From rest through every level of exercise to maximal exhaustion, PSV increased continuously in the ETA. The PSV in US increased from rest to 60% of VO2max, followed by small but not significant increases between the levels. The ETA had 11% to 16% higher blood pressure from 60% to 100% of VO2max. Discussion: TVI revealed that the ETA had higher PSV than that of the US during exercise at 70% to 100 % of VO2max, but not at rest and during mild exercise. PSV might be enhanced for two reasons, either increased contractile capacity or lower peripheral resistens. In view of the fact that the athletes` blood pressure was higher during exercise, this experiment indicates that endurance athletes may have enhanced contractile capacity, only observable during exercise.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Published by The Norwegian School of Sport Sciences. All rights reserved.