HIITting The Right Intensity: Intensity Matters For Chronic Inflammation And Body Composition In Older Adults

PURPOSE: To determine whether exercise intensity influences chronic inflammation and body composition adaptations to exercise in older adults. METHODS: This randomised controlled trial included apparently healthy older adults (n = 123, average age 72.0 ± 4.1 years, body mass index 25.8 ± 3.6 kg/m2) who completed three, 45-minute supervised exercise sessions per week for 6 months. Participants were randomised to low- (LIT; n = 37, 45-55% HRpeak), moderate- (MICT; n = 45, 60-70% HRpeak), or high- (HIIT; n = 41, 85-95% HRpeak intervals) intensity Aerobic exercise training. Dual-energy x-ray absorptiometry was used to quantify body composition and fasted, rested venepuncture with Multiplex immunoassay was used to assess inflammatory cytokines [interleukin (IL)-1β, IL-6, IL-10, IL-12, interferon (IFN)-y] at baseline, 3- and 6-months. RESULTS: There were no significant differences among groups in inflammatory cytokines (IL-1β, IL-6, IL-10, IL-12, IFN-y) at 3- or 6-months. However, all intensity groups demonstrated significant and clinically meaningful reductions in interleukin (IL)-1β (p < 0.001-0.005), IL-10 (p < 0.001-0.011), IL-12 (p < 0.001-0.005) and interferon (IFN)-y (p < 0.001-0.010) from 0-3 and 0-6 months. The MICT group demonstrated a reduction in IL-6 from 0-3 months (p < 0.001) and 0-6 months (p = 0.001), with comparable reductions in the HIIT group from 0-6 months (p = 0.002). Reductions in fat mass were similar between HIIT (p = 0.001) and MICT (p = 0.016) groups, and superior to the LIT group at 6 months. The MICT group demonstrated reductions in lean mass (LM) from 0-3 (p = 0.005) and 0-6 months (p = 0.050). In contrast, the HIIT group experienced a net improvement in body fat percentage (p = 0.017) and superior LM change at 6-months compared with the MICT group (p = 0.042). CONCLUSIONS: Exercise of any intensity can instigate clinically meaningful reductions in markers of chronic inflammation. In contrast, only HIIT reduced FM and maintained FFM in apparently healthy older adults. Higher intensity exercise should be recommended where appropriate to improve chronic inflammation and body composition in older adults.