The effect of high-intensity interval training on cardiovascular and cardiometabolic health markers in young adults

Background: Limited information related to changes in both the metabolic and blood profiles of healthy young adults engaging in either high-intensity interval training (HIIT) or moderate-intensity continuous training (MICT) modalities exists. The detrimental effects of sedentary lifestyles can be moderated and may be dependent on the intensity of the intervening activity. It is well known that regular physical activity (PA) can improve a person’s cardiorespiratory fitness (CRF) and therefore mitigate potential life-threatening effects of sedentary behaviours. Yet despite this, globally, approximately one out of every four adults fail to meet the minimum PA guidelines. Methods: Twenty-eight recreationally active adults from Nelson Mandela University (NMU) initially volunteered to participate in the study. The study was advertised on social media and via the NMU email MEMO database. Eight (n=8) participants were excluded from the study analysis as they failed to complete all the required testing sessions (illness: n=3; failure to attend 80% of sessions: n=2; lost interest: n=3), resulting in a total sample of 20 participants that were retained for analysis (HIIT (n=10) and MICT (n=10)). For inclusion to the study, all participants were required to: (i) be healthy before and during the testing period (ii) be between 18-35 years of age, and (iii) be free of injury before and during testing. Participants attended three training sessions per week for six weeks. HIIT and MICT interventions were matched for exercise load. Results: Within-group differences (i.e. pre- vs. post-intervention) were present, specifically for cardiovascular adaptations including maximal oxygen uptake (HIIT: +17.40%; MICT: +16.11%), gas exchange threshold (HIIT: +14.50%; MICT: +10.83%) and peak power output (HIIT: +38.92%; MICT: +33.79%), but not for cardiometabolic (p = 0.11 – 0.81). No between-group differences were evident for any measured parameters (p = 0.24-0.97), showing no clear preference for either HIIT or MICT modality. Conclusion: Acute improvements in CRF and metabolic biomarkers appeared to be independent of exercise intensity and were achievable within a relatively short time frame.Thesis (MHMS) -- Faculty of Health Sciences, 202