Abolished circadian rhythm of salivary cortisol in elite artistic gymnasts
Research highlights
▶ The circadian rhythm of salivary cortisol in elite artistic gymnasts is abolished. ▶ Female artistic gymnasts presented higher levels of morning salivary cortisol than female controls. ▶ Male and female artistic gymnasts had higher degree of psychological stress in comparison with controls. ▶ Female artistic gymnasts had higher morning and afternoon salivary cortisol levels and higher degree of stress than male ones.
Introduction
Stress is an ever-present reality for elite athletes. It is well documented that strenuous and prolonged physical activity in humans has been compared to chronic stress in humans by inducing alterations to hormonal responses to stress, including elevations of cortisol [1], [2].
The hypothalamus–pituitary–adrenal (HPA) axis plays an important role in maintaining physiological homeostasis under both basal and pathophysiological conditions. Repeated acute or chronic exposure to stress results in adaptive changes in the HPA axis. Acute intense exercise activates the HPA axis [3], while intense physical training, by acting as a chronic repeated stress, leads to a reduced responsiveness of the HPA axis [4]. These changes have been noted in both sexes and are dependent upon the duration, the intensity and the type of training or exercise [5]. Female athletes seem to be more vulnerable to physical stress than males [7].
The role of cortisol in athletic performance is an area of ongoing interest and research in sports medicine, sports psychiatry and sports psychology. Cortisol levels are easily and precisely assessed in saliva and therefore measurement of salivary cortisol has several advantages over the determination of serum cortisol especially in athletes during competition because it is a non-invasive, stress-free procedure, which increases subject compliance and permits the monitoring of HPA-axis physiology [8], [9]. Limited information is available concerning the diurnal variations of cortisol levels in elite athletes [10].
The major sports that require intensive physical training during childhood and adolescence are mainly gymnastics, both rhythmic and artistic. In contemporary gymnastics, requirements for international records have driven the hours of training to even exceed 30 h per week, compared to 15 h during the seventies and 20 h during the eighties.
The aim of this study was to evaluate the effects of intensive physical exercise and acute psychological stress during a high level athletic competition on the levels of salivary cortisol in elite artistic gymnasts (AGs). This study is unique in character, as all variables were assessed on the field of competition.
Section snippets
Experimental
The study included 239 caucasian athletes (elite gymnasts)—142 girls (aged 16.0 ± 1.6 years) and 97 boys (aged 16.8 ± 1.1 years) from 44 European countries, during the European Championship of Gymnastics held in Volos, Greece on April 2006.
Eighty one pubertal adolescents, who were recruited from public schools in Greece, not engaged in strenuous sports activities were used as controls (40 girls aged 16.0 ± 1.4 years and 41 boys aged 15.3 ± 2.0 years).
The study was conducted under the authorization of
Results
In both male and female AGs, the morning and afternoon values of salivary cortisol as well as the degree of reported psychological stress are presented in Table 1. No difference was found between the morning (AM) and the afternoon (PM) cortisol levels in both male and female athletes (Fig. 1).
In the control group, salivary morning cortisol was 11.6 ± 8.3 nmol/l (n = 29) in females and 9.1 ± 8.3 nmol/l (n = 35) in males, while the grade of psychological stress was 10 ± 7 (n = 28) for females and 8 ± 6 (n = 30)
Discussion
The present study demonstrates that in both male and female elite artistic gymnasts (AGs) intense exercise had a profound effect on salivary cortisol as reflected by the loss of diurnal rhythm. To our knowledge, few data on diurnal cortisol profiles have been reported in high level athletes. The lack of hormonal studies in elite athletes could be due to subject availability and potential objections of the ethics committee to authorise blood collection or blood sampling strategies. The choice of
Declaration of interest
There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding
This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.
Acknowledgments
We express our grateful thanks to Mr. Bruno Grandi, President of the International Federation of Gymnastics (F.I.G.) and to Mr. Dimitris Dimitropoulos, former President of the European Union of Gymnastics (U.E.G.), who provided all necessary facilities and greatly encouraged the fulfilment of this study.
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