Cardiac Structure and Cardiorespiratory Fitness in Young Male Japanese Rugby Athletes

Abstract

Limited data are available on athlete's heart for rugby athletes. This study aimed to investigate cardiac structure and its relationship with cardiorespiratory fitness in young Japanese rugby athletes. A prospective cross-sectional study using echocardiography and cardiopulmonary exercise testing (CPET) was conducted on 114 male collegiate rugby players. There was a higher prevalence of increased left ventricular (LV), atrial, and aortic dimensions in the young athletes than that in previously published reports, whereas the wall thickness was within the normal range. Anthropometry and CPET analyses indicated that the forwards and backs presented muscular and endurance phenotypes, respectively. Indexed LV and aortic dimensions were significantly larger in the backs than in the forwards, and the dimensions significantly correlated with oxygen uptake measured by CPET. On the four-tiered classification for LV hypertrophy, abnormal LV geometry was found in 16% of the athletes. Notably, the resting systolic blood pressure was significantly higher in athletes with concentric abnormal geometry than in the other geometry groups, regardless of their field positions. Japanese young athletes may exhibit unique phenotypes of cardiac remodeling in association with their fitness characteristics. The four-tiered LV geometry classification potentially offers information regarding the subclinical cardiovascular risks of young athletes.

Keywords: athlete’s heart; cardiopulmonary exercise testing; rugby; young athletes.

Figure 1

Distributions of dimensions and wall thicknesses of the left heart in young Japanese rugby athletes. Distributions are shown for the (a) left ventricle, (b) left atria, and (c) aorta. Red dotted lines signify the normal upper limit of the general population, according to the guidelines [10]. AOD, aortic root dimension; BSA, body surface area; IVSth, thickness of interventricular septum; LAD, left atrial dimension; LVEDD, left ventricular end−diastolic dimension; RWT, relative wall thickness.

Figure 2

Left ventricular geometry evaluated by (a) 2- and (b) 4-tiered classifications in young Japanese rugby athletes. The left ventricular geometry is classified according to the thresholds indicated by the red lines. NG, normal geometry; AB, abnormal geometry including concentric remodeling (CR), concentric left ventricular hypertrophy (CH), and eccentric left ventricular hypertrophy (EH); BSA, body surface area.