Allometric analysis of the association between cardiac dimensions and bodysize variables in 464 junior athletes

Empirically derived relationships between body size variables and cardiac d imensions have not been published previously for a large sample of male and female athletes. This process would inform scaling practice and facilitate intra- and inter-group comparisons of cardiac data. Therefore we investiga ted the relationships of body mass (BM), height and body surface area (BS) with a range of cardiac dimensions derived by echocardiography in 464 male and female elite junior athletes (age range 14-18 years; sporting allocatio n included rowers, cyclists, footballers, tennis players, swimmers and a mi scellaneous group). Initial linearity checks suggested that most of the rel ationships between the body size variables and cardiac dimensions were non- linear, thus precluding the simple ratio standard approach to scaling. Mult iple log-log least-squares linear regression confirmed commonality of slope s (between males and females, across the age range and between sporting gro ups) for all relationships involving BM and BS. Subsequent analyses of the slope exponent (b) for left ventricular dimensions supported previous data and were dimensionally consistent (LVM-BM, b = 0.91 +/- 0.11; LVM-BS, b = 1 .44+/-0.19; where LVM is left ventricular mass), except for left ventricula r internal dimension in diastole (LVIDd) (LVIDd-BM, b = 0.25+/-0.04). Data for the left atria internal dimension (LA) were also dimensionally consiste nt (LA-BM, b = 0.29+/-0.09); however, this was not the case for the right v entricular internal dimension in diastole (RVIDd) (RVIDd-BM, b = 0.76+/-0.1 4). It is possible that these results were due to a study-specific limitati on in the data range (LVIDd) and the geometric peculiarities of RVIDd compa red with LVIDd. The gender/age/sporting group x body size interaction facto r for virtually all relationships between height and cardiac dimensions was significant (P < 0.05), and thus whole-group b exponents could not be gene rated. Generally these data support previous small-sample research with ath letes, and suggest that allometric scaling, as opposed to simple ratio scal ing, should be adopted in studies of cardiac dimensions in athletes. This s hould allow, with minimal mathematical difficulty, the production of body-s ize-independent cardiac indices to be evaluated in laboratory or clinical w ork. Further research is required to develop normative 'allometrically deri ved' cardiac indices, and care should be taken to determine relationships i n specific population groups as well as to confirm commonality of slopes in multiple group comparisons. Caution is expressed regarding the use of heig ht as a scaling variable in future research.