Caffeine Augments the Lactate and Interleukin-6 Response to Moderate-Intensity Exercise

IntroductionThe release of interleukin (IL)-6 from contracting skeletal muscle is thought to contribute to some of the health benefits bestowed by exercise. This IL-6 response seems proportional to exercise volume and to lactate production. Unfortunately, high volumes of exercise are not feasible for all people. Caffeine augments the magnitude of increase in circulating IL-6 in response to high-intensity and long-duration exercise. Caffeine also increases circulating concentrations of lactate during exercise. We hypothesized that caffeine, ingested before short-duration, moderate-intensity exercise, would lead to greater circulating concentrations of lactate and IL-6 in a study population comprising both male and female individuals.MethodsTwenty healthy adults (10 men and 10 women age 25 +/- 7 yr (mean +/- SD)) completed 30 min of moderate-intensity cycle ergometer exercise, at an intensity corresponding to 60% peak oxygen uptake, after ingesting either caffeine (6 mg center dot kg(-1)) or placebo. Arterialized-venous blood was collected throughout each of the exercise sessions.ResultsCompared with placebo, caffeine increased circulating concentrations of lactate at the end of exercise (5.12 +/- 3.67 vs 6.45 +/- 4.40 mmol center dot L-1, P < 0.001) and after 30 min of inactive recovery (1.83 +/- 1.59 vs 2.32 +/- 2.09 mmol center dot L-1, P = 0.006). Circulating IL-6 concentrations were greatest after 30 min of inactive recovery (P < 0.001) and higher with caffeine (2.88 +/- 2.05 vs 4.18 +/- 2.97, pg center dot mL(-1), P < 0.001). Secondary analysis indicated sex differences; caffeine increased the IL-6 response to exercise in men (P = 0.035) but not in women (P = 0.358).ConclusionsIn response to moderate-intensity exercise, caffeine evoked greater circulating lactate concentrations in men and women but only increased the IL-6 response to exercise in men. These novel findings suggest that for men unwilling or unable to perform high-intensity and/or long-duration exercise, caffeine may augment the health benefits of relatively short, moderate-intensity exercise.