Abolished circadian rhythm of salivary cortisol in elite artistic gymnasts

Abstract

Objective The aim of this study was to evaluate the effects of intensive physical exercise and acute psychological stress during high level athletic competition as reflected on the levels of salivary cortisol in elite artistic gymnasts (AGs). Design The study included 239 AGs (142 females–97 males) who participated in the European Championship of Gymnastics in 2006 and 81 adolescents (40 females–41 males), matched for age, as controls. All athletes participated voluntarily in all or parts of the study, providing samples or data for each of the variables measured. Height, weight, body fat, lean body mass (LBM), bone age and Tanner stage of puberty were assessed and data concerning the time of thelarche, adrenarche and menarche as well as, the onset and the intensity (hours per week) of training were obtained. Methods Saliva samples were collected, the morning before training and in the afternoon shortly after the competition. From controls, the saliva samples were collected in the morning. Cortisol concentrations were measured using a chemiluminescence method. Acute stress was assessed using a questionnaire designed for the study. Results No difference was found between morning and afternoon salivary cortisol levels in both male and female AGs (females: AM: 15.45 ± 7.45 nmol/l vs PM: 15.73 ± 9.38 nmol/l; males: AM: 10.21 ± 5.52 nmol/l vs PM: 9.93 ± 13.8 nmol/l, p > 0.05). Female AGs presented higher levels of morning salivary cortisol than female controls ( p < 0.05). Both male and female AGs had higher degree of psychological stress in comparison with controls ( p < 0.001, p < 0.013, respectively). Female AGs had higher morning and afternoon salivary cortisol levels ( p < 0.01, p < 0.01, respectively) and higher degree of stress ( p < 0.003) than males. Conclusions In elite AGs the diurnal rhythm of salivary cortisol has been abolished, probably due to the strenuous training and competition conditions. Female AGs presented higher levels of morning salivary cortisol and psychological stress compared to both male AGs and female controls. The long term consequences of these modifications of the HPA axis remain to be elucidated.