A short study with 12 young men found that steady, moderate cycling lowered a mouth‑immune protein called SIgA right after the workout, while interval cycling didn’t change it. However, the levels of several antimicrobial peptides—including the one you’re interested in, LL‑37—stayed the same regardless of the exercise style.

This study aimed to examine the acute effects of continuous and interval cycling on salivary secretory immunoglobulin A (SIgA) and anti-microbial peptides. In a randomized crossover trial, 12 healthy young untrained men (22 ± 1 years) performed two exercise patterns: continuous exercise (CE) for 20-min cycling load equivalent to 70% maximal oxygen uptake (V·O_2max) and interval exercise (IE) for 20-min cycling exercise, with five sets of 2 min at 50% V·O_2max and five sets of 2 min at 90% V·O_2max. Saliva samples were collected at baseline and post-0 min and post-30 min after exercise. We evaluated salivary SIgA as well as salivary lysozyme, lactoferrin, human β-defensin-2, and LL-37 as the anti-microbial peptides at each time point. In the CE trial, the salivary SIgA secretion rate decreased immediately after exercise (p = 0.0002). However, in the IE trial, the salivary SIgA secretion rate did not change. In addition, the percentage change in salivary SIgA secretion rate immediately after exercise decreased in the CE as compared to the IE (CE: -37.6 ± 19.7% vs IE: 3.6 ± 33.6%, p = 0.0014). However, salivary lysozyme, lactoferrin, human β-defensin-2, and LL-37 secretion rates did not change from baseline to after exercise in both trials. These results suggest that salivary SIgA secretion may differ between acute CE and IE, whereas secretory responses to salivary anti-microbial peptides may not differ.