The Effects of Acute and Chronic Sprint-Interval Training on Cytokine Responses Are Independent of Prior Caffeine Intake

We examined the effect of acute and chronic sprint interval training (SIT), with or without prior caffeine intake, on levels of exercise-induced inflammatory plasma cytokines [interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α]. Twenty physically-active men ingested either a placebo (n = 10) or caffeine (n = 10) 1 h before each SIT session(13-s × 30-s sprint/15 s of rest) during six training sessions (2 weeks). The early (before, immediately after, and 45 min after the exercise) and late (24 and 48 h after the exercise) cytokine and creatine kinase (CK) responses were analyzed for the first and last training sessions. Plasma IL-6 and IL-10 peaked 45 min after the exercise, and then returned to basal values within 24 h (p < 0.05) in both groups on both occasions (p > 0.05). On both occasions, and for both groups, plasma TNF-α increased from rest to immediately after the exercise and then decreased at 45 min before reaching values at or below basal levels 48 h after the exercise (p < 0.05). Serum CK increased from rest to 24 and 48 h post-exercise in the first training session (p < 0.05), but did not alter in the last training session for the PLA group (p > 0.05). Serum CK was unchanged in both the first and last training sessions for the CAF group (p > 0.05). Two weeks of SIT induced a late decrease in the IL-6/IL-10 ratio (p < 0.05) regardless of caffeine intake, suggesting an improved overall inflammatory status after training. In conclusion, a single session of SIT induces muscle damage that seems to be mitigated by caffeine intake. Two weeks of SIT improves the late SIT-induced muscle damage and inflammatory status, which seems to be independent of caffeine intake.