Intense physical training may affect cellular membrane stability. Phase angle (PA) is a non-invasive measure related to cellular membrane composition and stability that is calculated from resistance and reactance and is obtained by bioelectrical impedance (BIA)⁽Reference VanderJagt, Huang and Chuang¹⁾. Previous reports have shown that PA is associated to age, gender and BMI⁽Reference Barbosa-Silva, Barros and Wang²⁾ but little is known about the sources of variation in PA among athletes. The aim of the present study was to investigate the determinants of PA in male elite athletes (≥3 h training daily, and participation in international competition). Healthy athletes (n 158; age 13–48 years) who participated in this cross-sectional observational study practiced the following specialist sports: adventure running, n 6; cycling, n 11; judo, n 7; long-distance running, n 27; short-distance running, n 14; soccer, n 50; swimming, n 13; triathlon, n 15; water polo, n 15. BIA was performed using a BIA 101-Q impedance analyser (RJL Systems, MI, USA) under a strict standardized procedure⁽Reference Barbosa-Silva, Barros and Wang²⁾. The BIA measurements were routinely carried out at 08.00 hours after ≥8 h fast and 16 h rest. All the subjects were of normal BMI and hydration status. The athletes were stratified according to age⁽Reference Barbosa-Silva, Barros and Wang²⁾ and the data for PA, weight, height and BMI are presented in the Table.

^a,b Means with unlike superscript letters in the same column were significantly different (ANOVA with Tukey's post-hoc test; P<0.005). The effect of age on PA was independent of BMI and sport specialism (MANOVA).

Figure. Association between PA and age for all athletes.

In agreement with previous findings⁽Reference Barbosa-Silva, Barros and Wang²⁾ PA was positively correlated with BMI (r 0.66; P<0.001). In contrast to previous reports⁽Reference Barbosa-Silva, Barros and Wang²⁾ PA was lower in adolescents than in young adults (Table), and increased steeply with age within the same specialty (soccer; Figure). Among athletes aged 10–19 years 57% of PA values were lower than the 5th percentile of a reference group⁽Reference Barbosa-Silva, Barros and Wang²⁾, in contrast to the other three age subgroups, for whom the corresponding values were 2%, 0% and 0%, respectively. The results suggest that the intense physical training, which is usual for elite athletes, may negatively influence PA of male adolescents, which might be related to cellular membrane stability.