Effects of High-Intensity Interval and Continuous Moderate Aerobic Training on Fitness and Health Markers of Older Adults: Systematic Review and Meta-Analysis

Background : High-intensity interval training (HIIT) promotes similar or superior gains in physical fitness and health compared to continuous moderate-intensity training (MICT) in young individuals. However, the effectiveness of HIIT in older adults is uncertain. Objective: This meta-analysis compared the effects of HIIT and MICT on cardiorespiratory fitness, body composition, vascular, metabolic, and hormonal variables, cognitive function, and quality of life in older adults. Methods : PubMed, Embase, Cochrane, Web of Science, Scopus, and SportDiscus databases were searched from inception until December 2023. Trials included adults ≥ 60 y. Hedge's effect sizes (g) were calculated and study quality and features of training interventions were tested as moderators Results : Twenty-nine trials including 1,227 subjects (65.4±3.3 y). HIIT and MICT elicited significant (p<0.021) and similar (p>0.156) ‘gs’ for VO2max (0.722 vs. 0.490), maximal workload/peak power output ratio (0.290 vs. 0.372), % fat (-0.297 vs. -0.262), glycemia (-0.273 vs. -0.334), systolic (-0.465 vs. -0.341), and diastolic blood pressure (-0.566 vs. -2.311). HIIT (p<0.04) but not MICT (p>0.170) produced significant ‘gs’ for fat mass (-0.245 vs. -0.103), waist circumference (-0.239 vs. -0.116), testosterone (0.339 vs. 0.170), and complex Stroop test (-0.595 vs. -0.250). Increases in the VO2max occurred only in controlled trials after HIIT but not MICT (Q=6.286, p=0.012; HITT-g=1.068, p<0.0001 vs. MICT-g=0.109, p=0.596) Conclusion : HIIT and MICT produced similar changes in most of the investigated variables. In trials with greater quality (controlled vs. non-controlled trials), cardiorespiratory gains were higher in HIIT vs. MICT. These findings suggest that HIIT might be suitable for improving fitness and health in older adults.