Abstract
IntroductionSalivary secretory immunoglobulin A (sIgA), saliva flow rate and plasma cortisol concentrations have been shown to be influenced by exercise, particularly the intensity exercise is performed at, and circadian variation. The autonomic nervous system partly regulates salivary secretion, but it is not yet known whether cortisol also explains some variation in salivary parameters.MethodsTwelve moderately trained male individuals (dot {V}{{text{O}}_2}peak legs: 46.2 ± 6.8 mL·kg−1·min−1) performed three 45-min constant load exercise trials in the morning: arm cranking exercise at 60%dot {V}{{text{O}}_2}peak arms; moderate cycling at 60%dot {V}{{text{O}}_2}peak legs; and easy cycling at 60%dot {V}{{text{O}}_2}peak arms. Timed saliva samples and blood samples for plasma cortisol concentration determination were obtained before, post, 2 h post, and 4 h post-exercise. Saliva was collected in an additional resting trial at the same time points.ResultsAt each time point for each exercise trial, negative correlations between cortisol and saliva flow rate (explaining 25 ± 17% of the variance, R2 = 0.002–0.46) and positive correlations between cortisol and sIgA concentration (explaining 8 ± 8% of the variance R2 = 0.002–0.24) were found. Saliva flow rate increased over time, whereas sIgA concentration and cortisol decreased over time for all trials (P < 0.05), there was no effect of time for sIgA secretion rate (P = 0.16).ConclusionThese results show a relationship between cortisol and saliva flow rate, which directly impacts on the concentration of salivary analytes. This study further confirms circadian variations in salivary parameters which must be acknowledged when standardising salivary data collection.
Highlights
Salivary secretory immunoglobulin A, saliva flow rate and plasma cortisol concentrations have been shown to be influenced by exercise, the intensity exercise is performed at, and circadian variation
Negative relationships between plasma cortisol concentration and saliva flow rate were found for all trials at all time points (Fig. 1)
Correlation coefficients between plasma cortisol concentration and secretory immunoglobulin A (sIgA) concentration were predominantly positive but were considerably lower (R2 up to 0.24; Table 1) than those found for the cortisol – saliva flow rate relationships (R2 up to 0.46; Fig. 1); none of these correlations reached significance (P > 0.05)
Summary
Salivary secretory immunoglobulin A (sIgA), saliva flow rate and plasma cortisol concentrations have been shown to be influenced by exercise, the intensity exercise is performed at, and circadian variation. Results At each time point for each exercise trial, negative correlations between cortisol and saliva flow rate (explaining 25 ± 17% of the variance, R2 = 0.002–0.46) and positive correlations between cortisol and sIgA concentration (explaining 8 ± 8% of the variance R2 = 0.002–0.24) were found. Exercise intensity is central in altering salivary parameters, whereby exercise of demanding nature, such as interval training (Mackinnon et al 1993) or marathon racing (Nieman et al 2002), can reduce saliva flow rate and sIgA secretion. Whilst dehydration (Walsh et al 2004) or upcoming illness (Neville et al 2010) have an impact on salivary protein concentration, to date, the source of this inter-individual sIgA variation in healthy, adequately hydrated individuals remains obscure
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