Self selection of athletes into sports via skeletal ratios

This study examined differences in physique and skeletal dimensions between 1146 elite Caucasian athletes classified into endurance, strength, speed, upper body or combined sports categories and controls, to test the hypothesis that athletes of certain types of sport would exhibit a distinct morphology commensurate with their task. Participants were measured by experienced anthropometrists using an internationally-recognised protocol to describe physique. This involved calculating the anthropometric somatotype in terms of fatness, musculoskeletal robustness and linearity. Further skeletal measures were acquired sufficient to describe an array of morphological indices: crural index (tibial height/femur length), skelic index (leg length/sitting height), androgyny index (biacromial breadth/bicristal breadth) and brachial index (forearm length/upper arm length). Significant inter-group differences in indices prevailed after adjustment for age. Endurance athletes had a high crural index and low brachial index, relative to controls. A low skelic index appears characteristic of female strength athletes while a low brachial index is typical of female endurance and strength athletes. Bayesian cluster analysis has shown the crural index in particular is a discriminant in phenotypic categorisation, in addition to the primary somatotype components of endomorphy, mesomorphy and ectomorphy. These findings are congruent with biomechanical imperatives to maximise force and/or minimise energy expenditure offering sports-specific advantage. Because the skeletal relationships do not respond to the conditioning stimulus in the same way adipose and muscle tissue do, the observed inter-group differences suggest a self-selection of athletes into sports in which they are likely to excel.