Effects of different exercise intensities or durations on salivary IgA secretion

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Purpose</jats:title> <jats:p>This study aimed to examine changes in salivary immunoglobulin A (s-IgA) secretion at different intensities or durations of acute exercise.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>Twelve healthy untrained young males were included in randomized crossover trials in Experiment 1 (cycling exercise for 30 min at a work rate equivalent to 35%, 55%, and 75% maximal oxygen uptake [<jats:inline-formula><jats:alternatives><jats:tex-math>$${\dot{\text{V}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>O<jats:sub>2max</jats:sub>]) and Experiment 2 (cycling exercise at 55% <jats:inline-formula><jats:alternatives><jats:tex-math>$${\dot{\text{V}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>O<jats:sub>2max</jats:sub> intensity for 30, 60, and 90 min). Saliva samples were collected at baseline, immediately after, and 60 min after each exercise.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Experiment 1: The percentage change in the s-IgA secretion rate in the 75% <jats:inline-formula><jats:alternatives><jats:tex-math>$${\dot{\text{V}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>O<jats:sub>2max</jats:sub> trial was significantly lower than that in the 55% <jats:inline-formula><jats:alternatives><jats:tex-math>$${\dot{\text{V}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>O<jats:sub>2max</jats:sub> trial immediately after exercise (− 45.7%). The percentage change in the salivary concentration of cortisol, an s-IgA regulating factor, immediately after exercise significantly increased compared to that at baseline in the 75% <jats:inline-formula><jats:alternatives><jats:tex-math>$${\dot{\text{V}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>O<jats:sub>2max</jats:sub> trial (+ 107.6%). A significant negative correlation was observed between the percentage changes in saliva flow rate and salivary cortisol concentration (r = − 0.52, P < 0.01). Experiment 2: The percentage change in the s-IgA secretion rate in the 90-min trial was significantly lower than that in the 30-min trial immediately after exercise (−37.0%). However, the percentage change in salivary cortisol concentration remained the same.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Our findings suggest that a reduction in s-IgA secretion is induced by exercise intensity of greater than or equal to 75% <jats:inline-formula><jats:alternatives><jats:tex-math>$${\dot{\text{V}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>O<jats:sub>2max</jats:sub> for 30 min or exercise duration of greater than or equal to 90 min at 55% <jats:inline-formula><jats:alternatives><jats:tex-math>$${\dot{\text{V}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mtext>V</mml:mtext> <mml:mo>˙</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>O<jats:sub>2max</jats:sub> in healthy untrained young men.</jats:p> </jats:sec>