High Intensity Interval Cycling Improves Physical Fitness in Trained Adults

Introduction: High intensity interval training (HIIT) is a specific type of vigorous intensity exercise characterised by periods of work over 85% maximum heart rate (HRmax). Numerous past studies have documented significant cardiovascular, metabolic, musculoskeletal, and body composition improvements with this type of training, traditionally with cycling Wingate tests. However, popular HIIT sessions outside of research typically incorporate weight-bearing impact, which limits large segments of the population from participating. Thus, a low-impact alternative in a practical format with parallel benefits is an imperative option that requires testing. Methods: Thirty-six trained adults were randomly assigned to one of two groups: Group HIIT or Group FIT. Group HIIT participants replaced a single 60-minute cardiovascular training session with 2, 30-minute high intensity indoor cycling sessions for 6 weeks. Group FIT maintained their current training routine. We measured blood pressure, peak oxygen consumption, fasting blood profile, body composition, and leg strength. Results: The HIIT intervention significantly improved all variables (p<0.05) except HDL cholesterol. Peak oxygen consumption and leg strength increased significantly for the HIIT group (+9.7% and 11.9% respectively) but not the FIT group. There were significant decreases in the HIIT group for blood pressure (-9.9%), fasting blood glucose (-7.0%), total cholesterol (-6.0%), LDL cholesterol (-7.8%), triglycerides (-16.3%) and fat mass (-1.1%). Conclusion: Adding high intensity interval cycling to the routine of trained adults improved physical fitness. Our results suggest that replacing one bout of moderate intensity exercise with two 30-minute bouts of cycling HIIT is an effective, low impact option to improve cardiovascular, metabolic and musculoskeletal fitness, as well as body composition.