| Summary: | Chronic low-grade inflammation plays a key role in the development of insulin resistance and type 2 diabetes mellitus (T2DM). Exercise is known to reduce inflammation, although the underlying mechanisms responsible are not fully elucidated. One proposed mechanism is reduced expression of pro-inflammatory toll-like receptors (TLRs) on immune cells after exercise training. High intensity interval training (HIIT), when compared to traditional moderate-intensity continuous training (MICT), may result in superior cardiovascular and metabolic benefits but the impact of HIIT on inflammation has not been adequately studied. The aim of this thesis was to compare two weeks of HIIT to MICT for improving cardiometabolic risk factors and markers of inflammation, including TLRs, in previously inactive adults diagnosed with prediabetes.
Inactive adults with prediabetes (N=39, age 30 – 65 years) were recruited and randomly assigned to an exercise intervention involving 10 days of progressive HIIT (4-10 X 1-min @ ~85% peak heart rate [HRPEAK] 1-min rest periods) or MICT (20-50 min @ ~60% HRPEAK) matched for estimated external work. Before and ~48-72 hr after the final training session, participants completed a maximal oxygen uptake (VO₂PEAK) test and markers of inflammation and cardiometabolic health were measured.
The central hypotheses that HIIT would result in greater improvements in cardiometabolic health and cause a larger reduction in markers of inflammation were not supported. Both HIIT (1.8 ± 0.4 vs. 1.9 ± 0.4 L/min, pre vs. post) and MICT (1.8 ± 0.5 vs. 1.9 ± 0.5 L/min, pre vs. post) were equally effective at improving VO₂PEAK (p<0.001). TLR4 expression was reduced on lymphocytes and monocytes after both HIIT and MICT (P<0.05) and on neutrophils after MICT only (p<0.01). TLR2 on lymphocytes was also significantly reduced after both HIIT and MICT (p<0.05). Plasma inflammatory cytokines and insulin were unchanged after training in both groups but MICT led to a reduction in fasting plasma glucose (P<0.05, 5.9 ± 1.0 vs. 5.6 ± 1.0 mmol/l, pre vs. post).
This study further supports HIIT as a viable training option for previously inactive adults at elevated risk of T2DM. However the increased duration of exercise associated with more traditional MICT may provide a greater stimulus reducing neutrophil TLR4 and lowering fasting glucose when compared to HIIT. === Graduate Studies, College of (Okanagan) === Graduate
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