A short study in 14 healthy young men found that a 30‑minute bike ride at any intensity didn’t change the mouth’s LL‑37 antimicrobial peptide, but doing a moderate‑intensity ride for 60‑90 minutes did raise LL‑37 levels. Other mouth peptides (lactoferrin, lysozyme, HBD‑2) responded differently to intensity and time.

Antimicrobial peptides, key players of innate mucosal immunity in the oral cavity, exert antibacterial and bacteriolytic effects. This study aimed to clarify the effects of acute exercise at different intensities and durations on salivary antimicrobial peptide levels. In a randomized crossover trial, 14 young healthy untrained men performed intensity trials [cycling at 35%, 55%, and 75% of maximal oxygen uptake (V&#x307;o_2max) for 30 min] and duration trials (cycling at 55% V&#x307;o_2max for 30, 60, and 90 min). Saliva samples were collected at baseline and 0 and 60 min after exercise. In intensity trials, the change in salivary lactoferrin levels from baseline to 0 min after 30 min exercise was greater at 75% V&#x307;o_2max exercise intensity compared with that at 35% V&#x307;o_2max. Furthermore, the change in salivary human &#x3b2;-defensin-2 (HBD-2) levels was greater at 75% V&#x307;o_2max compared with that at 35% and 55% V&#x307;o_2max. Salivary lysozyme levels increased after exercise, independent of exercise intensity. However, salivary LL-37 levels did not change after exercise at any intensity. In addition, in duration trials, the change in salivary levels of LL-37 and HBD-2 from baseline to 0 min after exercise at 55% V&#x307;o_2max was greater after 60 and 90 min of exercise compared with that after 30 min of exercise. However, salivary lactoferrin and lysozyme levels increased after exercise, independent of exercise duration. Our findings suggest that secretory responses to acute exercise with exercise intensity and duration differ among salivary antimicrobial peptides.<b>NEW &amp; NOTEWORTHY</b> We investigated the effects of acute exercise at different intensities and durations on the immune response to salivary antimicrobial peptides in young healthy men. Levels of four salivary antimicrobial peptides increased after exercise dependently or independently of exercise intensity and duration, whereas some salivary antimicrobial peptides did not change after exercise. These findings suggest that the secretory responses to acute exercise with different intensities and durations differ among salivary antimicrobial peptides.