Cardiac adaptation to training and decreased training loads in endurance athletes: a systematic review

INTRODUCTION: Changes in echocardiographic standard measurements as a consequence of training and detraining in elite or subelite athletes have not been comprehensively studied. METHODS: We identified 200 potentially relevant studies from 1966 to June 2006 and eliminated 187 studies that did not fulfil the objectives of the study. We identified 13 studies with echocardiographic assessment of heart adaptation following variation in training loads in elite or subelite endurance-trained athletes. We performed a meta-analysis by studying the changes in the left ventricular end-diastolic (LVEDD), left ventricular end-systolic (LVESD), left ventricular posterior wall (LVPW) and interventricular septum thickness (IVST) dimensions induced by training. RESULTS: A significant positive overall effect size on echocardiographic outcomes was found following training, using the fixed effect model on LVPW, LVEDD, LVESD and IVST. LVPW and LVEDD were significantly higher following training. CONCLUSION: Studies reported an increase in LVEDD and LVPW, following endurance training. However, the heterogeneity of the studies and the sensitivity of echocardiography technique can be two reasons, for which the results do not allow to state unequivocally that the adaptation to endurance training of highly trained hearts stems from increments of diastolic diameter of the left ventricle and lateral wall of the left ventricle (LVPW).