The Effects of High-Intensity Interval Training vs. Moderate-Intensity Continuous Training on Heart Rate Variability in Physically Inactive Adults.

Ken Alford,Hyun Jung,Abdullah Alansare,Sukho Lee,Tommie Church

doi:10.3390/ijerph15071508

Abstract

Physically inactive adults are prevalent worldwide. This study compared the effects of short-term high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on heart rate variability (HRV) in physically inactive adults as a preliminary study. Thirteen physically inactive male adults (27.5 ± 3.80 years) were randomly assigned to HIIT (N = 7) or MICT (N = 6). The HIIT program consisted of 20 min of interval training with cycling to rest ratio of 10/50 s at ≥90% HRpeak, while the MICT program consisted of 40 min of continuous cycling at 60–75% HRpeak. Both groups completed eight sessions of training within two weeks. Time and frequency domains of HRV were measured for 20 min with Actiwave-Cardio monitor (CamNtech, UK). The number of R-R interval and inter-beat interval (IBI) were significantly improved (p < 0.05) in both HIIT and MICT programs following eight sessions of training. A significant interaction effect for group by time was found in the lnLF/HF ratio (p < 0.05) where it was only improved in the HIIT group from pre- to post-test. The HIIT program is superior to MICT in improving HRV in physically inactive adults. The HIIT program can be applied as a time-efficient program for improving cardiac-autoregulation.

Highlights

Physical inactivity, which is an independent risk factor for several chronic diseases, is globally prevalent [1]
Average HR and rate of perceived exertion (RPE) were significantly higher in the high-intensity interval training (HIIT) program compared to the moderate-intensity continuous training (MICT) program (t = 2.489, t = 4.048, p < 0.05 respectively)
The main findings were that both HIIT and MICT programs significantly improved the systolic blood pressure and time domains of heart rate variability (HRV) including the number of R-R interval and inter-beat interval (IBI)

Summary

Introduction

Physical inactivity, which is an independent risk factor for several chronic diseases, is globally prevalent [1]. Being physically inactive increases risk factors for mortality including cardiovascular diseases, cancer, and diabetes [4,5]. Shifting to an active lifestyle by being involved in physical activity programs would prevent such pathologies and improve overall health [6]. The World Health Organization (WHO) generally recommends adults to engage in moderateintensity of physical activity for 150 min/week to maintain their cardiovascular health [1]. Many health organizations including WHO emphasize the importance of physical activity programs, the number of inactive adults remains high [2,3]. The lack of time seems to be the main contributor to the prevalence of physical inactivity among adults [7].

Methods

Discussion

Conclusion