Effects of high intensity interval training on cardiorespiratory fitness and salivary levels of IL-8, IL-1ra, and IP-10 in adults with asthma and non-asthma controls

The purpose of this study was to determine whether high intensity interval training (HIIT) would lead to improvements in 1) maximal VO2, VE, VE/VCO2, and VE/MVV, and/or 2) resting salivary concentrations of pro-inflammatory markers Interleukin (IL-8), interferon-gamma-inducible-protein (CXCL10/IP-10)) and anti-inflammatory marker IL-1 receptor antagonist (IL-1ra) in adults with well-controlled asthma compared to non-asthma controls.Participants completed a maximal exercise test at the beginning (T1) and end (T2) of a 6-week HIIT intervention; saliva samples were obtained at the beginning and 30 min following the first (T1) and last (T2) exercise session.Adults with asthma (n = 20; age: 21.4 ± 2.4 years) and non-asthma controls (n = 12; age: 22.5 ± 3.4 years) completed the intervention. VO2max increased from T1 to T2 in both groups (asthma T1 32.9 ± 8, T2 38.6 ± 8.2 ml/kg/min; controls T1 34.5 ± 11.8, T2 38.9 ± 12.3 ml/kg/min). VEmax also increased in both groups (asthma T1 97.7, T2 110.8 units, p < 0.001, hp2 = <0.04; control T1 106.3, T2 118.1, p < 0.001, hp2 0.02). An increase in VE/VCO2 (F(1, 10)=22.11, p = 0.001) and VE/MVV (F(1, 10) = 111.30, p < 0.001) was observed in the control group; no differences were observed in the asthma group. No differences in IL-8 or IL-1ra were observed between groups. In the asthma group, resting salivary IP-10 concentrations significantly decreased from T1 (0.025 pg/ug protein) to T2 (0.015 pg/ug protein, p = 0.039, hp2= 0.3 (moderate effect)).A 6-week HIIT intervention led to a similar increase in VO2max and VEmax in those with and without asthma, and a decrease in resting salivary IP-10 levels among adults with asthma.