Impact of high-intensity interval training on vascular endothelial function in young adults

Thesis Abstract

The increasing prevalence of cardiovascular risk factors among young adults necessitates investigation into non-pharmacological interventions that can enhance vascular health, particularly vascular endothelial function, which is a key predictor of cardiovascular morbidity and mortality. Despite growing interest in high-intensity interval training (HIIT) as a time-efficient exercise modality, there remains limited empirical evidence regarding its specific effects on endothelial function in young adult populations. This study aims to evaluate the impact of a structured 8-week HIIT program on vascular endothelial function among healthy young adults aged 18–25 years. The specific objectives include assessing changes in flow-mediated dilation (FMD) of the brachial artery, serum nitric oxide levels, and circulating markers of endothelial activation before and after the intervention, and exploring the potential mediating role of oxidative stress and inflammatory markers. The research employs a quasi-experimental design with a pre-test/post-test control group configuration. The study population comprises 60 healthy young adults recruited from university campuses through stratified random sampling, with 30 participants assigned to the intervention group and 30 to the control group. The intervention group undergoes thrice-weekly supervised HIIT sessions, each lasting approximately 30 minutes, employing a protocol of 4-minute high-intensity bouts at 85–95% maximal heart rate interspersed with 3-minute active recovery periods at 50–60% maximal heart rate. The control group maintains their habitual activity levels without additional exercise intervention. Data collection involves ultrasonic assessment of brachial artery FMD, blood sampling for biochemical analysis of nitric oxide metabolites, endothelin-1, C-reactive protein (CRP), and malondialdehyde (MDA) levels. Validity and reliability of ultrasound measures are ensured through calibration and assessor training, while biochemical assays utilize standardized ELISA kits. Data analysis employs paired and independent samples t-tests, analysis of covariance (ANCOVA) to control for baseline differences, and multiple regression analysis to examine predictors of endothelial function improvements. The theoretical framework is grounded in the Endothelial Shear Stress Theory, which posits that exercise-induced shear stress modulates endothelial nitric oxide synthase activity, thereby improving endothelial function. The study is expected to demonstrate significant improvements in FMD (p < 0.01) and serum nitric oxide levels (p < 0.05) in the intervention group compared to controls, alongside reductions in oxidative stress and inflammatory markers. These biochemical and functional improvements suggest that HIIT stimulates favorable endothelial adaptations possibly mediated by increased shear stress and decreased oxidative damage. The findings will contribute to the growing body of evidence supporting HIIT as an effective strategy for vascular health promotion among young adults, with potential implications for early prevention of cardiovascular disease. This research advances current understanding by quantitatively elucidating the mechanistic pathways through which HIIT influences endothelial function, filling existing gaps in literature regarding young, healthy populations. It recommends incorporating HIIT into health promotion programs targeting vascular health and calls for further longitudinal studies to examine the sustained effects of intermittent high-intensity exercise. Ultimately, the study underscores the role of structured physical activity interventions in fostering early cardiovascular resilience, promoting healthier lifestyles among youth, and informing policy development for youth-oriented preventive health strategies.