In einer Untersuchung mit 14 männlichen Schwimmern wurde festgestellt, dass vor Belastung ein signifikanter Einfluss der Tageszeit auf die Variablen IgA-Spiegel, IgA-Sekreationshöhe und -Speichelflusshöhe sowie Kortisolspiegel und -Speichelflusshöhe besteht. Kein signifikanter Einfluss wurde auf die Akutreaktionen der Variablen nach Belastung ermittelt. Objective: To examine whether time of day significantly affects salivary cortisol and IgA levels before and after submaximal swimming. Methods: Fourteen male competitive swimmers (mean (SD) age 18 (3.2) years) volunteered to participate in the study. In a fully randomised, cross over design, each subject performed 5 x 400 m front crawl at 85 (1.2)% of their seasonal best time (277 (16) seconds), with one minute rest between each 400 m, at 0600 and 1800 hours on two separate days. Timed, unstimulated saliva samples were collected before and after exercise. Saliva samples were analysed for cortisol and IgA by radioimmunoassay and single radial immunodiffusion respectively. Results: Significant time of day effects (am and pm respectively) were observed in IgA concentration (0.396 (0.179) v 0.322 (0.105) mg/ml, p<0.05), IgA secretory rate (0.109 (0.081) v 0.144 (0.083) mg/min, p<0.01), and saliva flow rate (0.31 (0.23) v 0.46 (0.22) ml/min, p<0.001) before exercise (all values mean (SD)). Differences in cortisol levels before exercise (1.09 (0.56) v 0.67 (0.94) µg/dl) approached significance (p = 0.059). The exercise protocol did not significantly affect IgA concentration and secretory rate (p>0.05) but, in comparison with values before exercise, caused significant alterations in cortisol (p<0.01) and saliva flow rate (p<0.01). There was no significant interaction effect of time of day by exercise on any salivary variables measured (p>0.05). However, most of the values of the salivary variables before exercise were significantly inversely related to their exercise induced response (p<0.05). Conclusion: These results suggest a significant circadian variation in the variables measured before exercise, without showing a significant effect on their acute responses to exercise.
© Copyright 2002 British Journal of Sports Medicine. BMJ Publishing Group Ltd of the BMA. All rights reserved.