The effect of high-intensity aerobic interval training on markers of systemic inflammation in sedentary populations

This study examined the effects of high-intensity interval training (HIIT; 30 s sprint, 4-5 min passive recovery) and prolonged intermittent sprint training (PIST; 10 s sprint, 2-3 min moderate exercise) on the systemic inflammatory markers C-reactive protein (CRP) and tumor necrosis factor-α (TNF-α), aerobic capacity, and anthropometry in a middle-aged, sedentary population.

Fifty-five sedentary adults (age 49.2 ± 6.1 years) were randomised into HIIT (n = 20), PIST (n = 21), or a sedentary control group (CTRL n = 14). HIIT and PIST performed three training sessions per week for 9 weeks on a cycle ergometer, matched for total high-intensity time, while CTRL continued normal sedentary behaviours. Pre- and post-intervention testing involved measures of anthropometry, peak oxygen consumption (VO_2peak), and venous blood collection for analyses of CRP and TNF-α.

HIIT and PIST increased VO_2peak compared to CTRL (+3.66 ± 2.23 and 3.74 ± 2.62 mL kg min^-1). A group × time interaction (p = 0.042) and main effect of time (p = 0.026) were evident for waist girth, with only HIIT showing a significant reduction compared to CTRL (-2.1 ± 2.8 cm). TNF-α and CRP showed no group × time interaction or time effect (p > 0.05).

In sedentary individuals, 9 weeks of HIIT or PIST were effective to improve aerobic capacity; however, only HIIT significantly reduced waist girth and WHR compared to CTRL. Markers of systemic inflammation remained unchanged across all groups. Accordingly, for inflammation and VO2_peak, the distribution of sprints and the active or passive recovery periods are inconsequential provided that total duration of high-intensity efforts is similar.