Effects of different exercise intensities or durations on salivary IgA secretion

This study aimed to examine changes in salivary immunoglobulin A (s-IgA) secretion at different intensities or durations of acute exercise.

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 [ \({\dot{\text{V}}}\) $\dot{\text{V}}$ O_2max]) and Experiment 2 (cycling exercise at 55% \({\dot{\text{V}}}\) $\dot{\text{V}}$ O_2max intensity for 30, 60, and 90 min). Saliva samples were collected at baseline, immediately after, and 60 min after each exercise.

Experiment 1: The percentage change in the s-IgA secretion rate in the 75% \({\dot{\text{V}}}\) $\dot{\text{V}}$ O_2max trial was significantly lower than that in the 55% \({\dot{\text{V}}}\) $\dot{\text{V}}$ O_2max 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% \({\dot{\text{V}}}\) $\dot{\text{V}}$ O_2max 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.

Our findings suggest that a reduction in s-IgA secretion is induced by exercise intensity of greater than or equal to 75% \({\dot{\text{V}}}\) $\dot{\text{V}}$ O_2max for 30 min or exercise duration of greater than or equal to 90 min at 55% \({\dot{\text{V}}}\) $\dot{\text{V}}$ O_2max in healthy untrained young men.