Effects of High-Intensity Circuit Training in Obese and Overweight Population: A Randomized Clinical Trial

Background: Obesity is a serious risk for various cardiovascular diseases and is often managed with increased physical activity and exercise. The purpose of this study is to investigate the effects of a minimal dose, High-Intensity Circuit Training (HICT) program on a range of cardiovascular risk factors in obese and overweight individuals. Methods: The trial was prospectively registered with Cyprus National Bioethics Committee ΕΕΒΚ/ΕΠ/2017/38 29 th October 2017. A total of 30 participants were randomly allocated to HICT-group (n = 15) or to a no exercise control-group (n = 15). Participants in the HICT-group trained for 36-minutes, twice a week (18-minutes per session) for 8 weeks in total. The program consisted of 2 circuits of 6 exercise stations of 1min at 50-60% of Heart Rate Reserve (HRR) which progressed to 70-85% of HRR after the first two weeks, alternating with 1min active rest at 40-50% of HRR which progressed to 50-60% of HRR. Approximately 12 repetitions were performed per station. Body composition, blood markers and physiological variables, cardiorespiratory fitness and isometric strength were measured at baseline and post-intervention. Findings: Significant and meaningful improvements were demonstrated in cardiorespiratory fitness, several body composition variables, isometric strength of the left (non-dominant) lower limb and several physiological variables. No significant changes were revealed to the biochemical parameters or the strength of the right (dominant) limp. Conclusion: The results of the study suggest that a low-frequency, circuit training program with high intensity lasting only for 18-minutes twice a week is the minimum required dose in reducing at least some of the cardiovascular risk factors, in obese and overweight population.