Purpose: This study investigated the effect of caffeine consumed with and without carbohydrate (CHO) on immunoendocrine responses after exercise.
Methods: On four occasions, 12 recreational male cyclists cycled for 2 h at 65% V O2max. Sixty minutes before exercise, participants ingested 6 mg.kg(-1) body mass of caffeine (CAF) or placebo (PLA), then during exercise they consumed a 6% CHO or placebo (PLA) drink, providing CAF/CHO, PLA/CHO, CAF/PLA, and PLA/PLA conditions.
Results: f-MLP-stimulated neutrophil oxidative burst responses were significantly higher after exercise on CAF/CHO and PLA/CHO (both P<0.05) than PLA/PLA when expressed as a percentage of baseline value. The response on CAF/PLA tended to be higher than PLA/PLA at this point (P=0.056). No significant differences between CAF/CHO, PLA/CHO, and CAF/PLA were observed after exercise; however, only PLA/CHO showed no significant postexercise decline. Coingestion of CAF/CHO significantly attenuated epinephrine (P<0.05) and IL-6 (P<0.05) responses that occurred after ingestion of CAF alone (CAF/PLA) and significantly attenuated the transient alterations in circulating leukocyte (P<0.05) and neutrophil (P<0.01) counts. Plasma cortisol concentration was significantly lower on PLA/CHO than CAF/PLA and PLA/PLA after exercise (P<0.05). Perceived exertion during exercise was significantly lower on CAF/CHO than the other three trials (P<0.05).
Conclusion: Taken together, this suggests that coingestion of caffeine and CHO has greater influence on immunoendocrine responses than neutrophil functional responses to prolonged exercise.