Caffeine Augments the Lactate and Interleukin‐6 Response to Moderate‐Intensity Exercise in Men But Not Women

Abstract

The release of interleukin 6 (IL‐6) from contracting skeletal muscle is thought to contribute to some of the health benefits bestowed by exercise. This IL‐6 response appears proportional to exercise volume. Unfortunately, high volumes of exercise are not feasible for all people. Caffeine augments the magnitude of increase in circulating concentration of IL‐6 in response to high‐intensity and long‐duration exercise, in men. Caffeine is also known to increase circulating concentrations of lactate during exercise. One of the mechanisms thought to contribute to IL‐6 release from exercising skeletal muscle is lactate production. We hypothesized that caffeine, ingested prior to moderate‐intensity exercise, would lead to greater circulating concentrations of lactate and IL‐6 in a study population comprising both men and women. 15 healthy adults (9 males and 6 females, aged 26±7 years, (mean ± SD)) completed 30‐minutes of moderate‐intensity cycle ergometer exercise, equivalent to the ventilatory threshold, after ingesting either caffeine (6 mg/kg) or placebo. Arterialized‐venous blood was collected throughout each of the exercise sessions. Compared with placebo, caffeine increased end‐exercise circulating concentrations of lactate (5.72±3.95 vs. 7.14±4.66 mmol/L, P<0.001) but not end‐exercise IL‐6 (1.84±0.97 vs. 2.37±1.04 pg/mL, P=0.139). However, when women were excluded from the analysis, caffeine augmented (P=0.04) the magnitude of increase of end‐exercise IL‐6 concentration (1.80±0.86 vs. 2.57±1.21 pg/mL); this effect was further exaggerated after 30‐minutes of inactive recovery (3.81±2.32 vs. 5.06±3.22 pg/mL). Noteworthy, caffeine evoked greater end‐exercise lactate concentrations in data sets containing only men (P=0.02) and only women (P=0.002) but did not influence the IL‐6 response in women (P=0.94). Our preliminary data imply that in men unable/unwilling to perform high‐intensity and/or long duration exercise, caffeine may potentially enhance the IL‐6 mediated health benefits of relatively short, moderate intensity exercise.