title: Effects of chronic exercise training on left ventricular dimensions and function in young athletes.
abstract: BACKGROUND
  Exercise training-induced hemodynamic and electrophysiological changes in the myocardium lead to physiological left ventricular (LV) hypertrophy with preserved cardiac contractility and function, which differentiates it from hypertrophic cardiomyopathy, the latter being responsible for a third of sudden deaths in young athletes. The extent and mechanisms of cardiac adaptation to aerobic training are still poorly understood, which is of concern given the increasing involvement of young athletes in intensive training regimens.
  
  
  OBJECTIVE
  The purpose of this study was to determine the effect of sports training on LV morphology and function at rest in adolescent boys.
  
  
  METHODS
  Anthropometric measurements, estimation of body composition and resting M-mode 2-D echocardiography were performed in twenty-four boys (aged 15-16 years), 12 swimmers and 12 soccer players. LV systolic and diastolic function were evaluated by pulsed wave Doppler measurements in four-chamber apical view.
  
  
  RESULTS
  The swimmers were significantly heavier and had greater fat-free body mass (p < 0.01) than the soccer players. LV dimensions were strongly associated with body characteristics. Fifty percent of the swimmers exhibited end-diastolic LV internal chamber diameter above normal (> 54 mm) but no indication of ventricular hypertrophy. The swimmers had greater LV end-systolic and end-diastolic dimension than the soccer group (53.62 +/- 2.38 mm and 32.73 +/- 1.70 mm vs. 47.59 +/- 3.32 mm and 28.68 +/- 2.52 mm respectively). The differences between the groups persisted after allometric correction for body dimensions. The soccer group displayed significantly greater mean values for relative end-diastolic wall thickness (p < 0.01) but both groups showed eccentric LV enlargement (< 0.44 mm), especially the swimmers (p < 0.01).
  
  
  CONCLUSIONS
  Both groups showed an eccentric LV hypertrophy pattern. The swimmers, in particular, revealed high levels of chamber dilatation and systolic volume at rest, consistent with better venous return due to greater frequency and intensity of aerobic training.
authors.affiliation: Faculdade de Educação Física e Desporto, Universidade Lusófona de Humanidades e Tecnologias, Lisboa, Portugal. raquel_barreto@sapo.pt
authors.forename: Raquel Barreto
authors.initials: RB
authors.lastname: Madeira
authors.forename: Marisa
authors.initials: M
authors.lastname: Trabulo
authors.forename: Francisco
authors.initials: F
authors.lastname: Alves
authors.forename: José Gomes
authors.initials: JG
authors.lastname: Pereira
mesh_terms: D000293:Adolescent; D015444:Exercise; D006352:Heart Ventricles / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D009929:Organ Size; D013177:Sports / Q000502:physiology*; D016277:Ventricular Function, Left