The increase in plasma IL-6 following sprint interval training does not depend on total sprint volume

Abstract

The magnitude of the beneficial increase in plasma interleukin-6 (IL-6) with exercise is greater with continuous exercise of higher intensity and longer duration. However, it is unknown whether a greater volume of supramaximal interval exercise also enhances the IL-6 response. Therefore, the aim of the present study was to compare the effects of two sprint interval training (SIT) protocols involving different volumes of sprint exercise on plasma IL-6 levels. Nine healthy young men (age: 244 y, BMI: 23.33.1 kg·m-2, V̇O2max: 426 mL·kg-1·min-1) completed three experimental trials in randomised order, including ‘classic’ SIT (4x30-s ‘all-out’ cycle sprints within a 22-min session), reduced-exertion high-intensity interval training (REHIT; 2x20-s ‘all-out’ cycle sprints within a 10-min session), and a control condition (seated rest). Blood samples were collected pre-exercise and 0-, 30-, and 90-min post-exercise, and analysed for lactate and IL-6. Blood lactate levels peaked directly post-SIT (1.50.2 mM to 11.92.5 mM; p<0.001) and REHIT (1.70.4 to 9.13.1 mM; p<0.001). Plasma IL-6 levels peaked 30-min post-exercise (0.840.12 to 1.310.17 pg·mL-1 for SIT, p=0.003; 0.750.09 to 1.180.36 pg·mL-1 for REHIT, p=0.028). Compared to the control trial, IL-6 iAUC was significantly higher for both SIT (p=0.002) and REHIT (p=0.013), with no significant difference between SIT and REHIT. In conclusion, we demonstrate that the increase in plasma IL-6 levels is similar for two SIT protocols involving a 3-fold difference in sprint exercise volume (120 s vs. 40 s). Our data provide support for a possible role of glycogenolysis in the IL-6 response to SIT.