Exercise as it relates to Disease/The Benefit of High-Intensity Interval Training (HIIT) on Cardiometabolic Disease

This is an analysis of the journal article "High-intensity interval training in patients with lifestyle-induced cardiometabolic disease: a systematic review and meta-analysis" by Wetson et al. (2014).



What is the background to this research?
Cardiometabolic diseases, such as type II diabetes, atherosclerotic, cardiovascular disease, and the metabolic syndrome are noncommunicable diseases that become the top major killers during the past decade. Medication is an effective way for cardiometabolic diseases treatment, however, lifestyle modification is the first-line approach that is strongly recommended to prevent the occurrence of the diseases. Lifestyle modification programs including dietary and physical activity, but the evidence shows that exercise may decrease cardiometabolic diseases independent of dietary intervention.

Despite the evidence that exercise is a good method for health and disease prevention, data from WHO indicated that more than 80% of the adolescent population has insufficient physical activities. A common barrier for individuals who lack engagement in physical activity is a lack of time. Based on 2008 Physical Activity Guidelines, 1 minute of vigorous exercise counts for 2 minutes of moderate-intensity exercise. Substituting some vigorous activity for some moderate-intensity activity become a way to improve fitness in a more time efficient method. High-Intensity Interval Training (HIIT) is one types of vigorous activity. HIIT is characterized by short periods of high-intensity aerobic exercise (>90% VO2max) separated recovery periods of lower-intensity aerobic exercise or rest. Several recent studies indicate that HIIT may result in equal or superior improvement of cardiovascular fitness compared with Moderate-Intensity Continuous Training (MICT). Therefore, the study evaluates the benefit of HIIT on cardiometabolic diseases as an option of time efficient exercise.

Where is the research from?
The study was conducted by researchers from School of Human Movement Studies, The University of Queensland, Brisbane, Australia and Department of Circulating and Medical Imaging, Faculty of Medicine, Norwegian University of Sciene and Technology, Trondheim, Norway. The research was published in British Journal of Sports Medicine and it is free to read online or download as a PDF.

What kind of research was this?
The Systematic review of randomized control trials (RCT) and meta-analysis study is an evaluation of the benefits of HIIT on cardiometabolic diseases. According to the Levels-of-Evidence Rating, Systematic review of RCT is categorized as level I, which demonstrates a valid and substantial study towards HIIT on cardiometabolic diseases. However, an in depth assessment of the study should be reviewed by the method of critical appraisal, which critiques the overall quality of the study. The PEDro Scale, a form of critical appraisal, confirms the quality of the Systematic review of RCT scoring the study 7.35/10, overall displaying a valid type of research.

What did the research involve?
The research compared the mean difference of preintervention and postintervention cardirespiratory fitness (CRF) or VO2 max between HIIT and MICT. Articles were found from electronic databases including MEDLINE, PubMed, EMBASE, and Cinahl from the earliest available date to April 2013. Those are appropriate databases for biomedical research. The use of minimum 2 databases are needed to perform a reasonable depth of the topic.

Articles that were included in this study only consisted of full text resources and RCT. RCT is the most accurate way to determine the cause-effect relation and effectiveness of the treatment.

What were the basic results?
The result of the study shows the effect of HIIT compared to MICT on the different aspects of cardiometabolic risks. There is an improvement of VO2 max from HIIT and MICT (increase by 19.4% and 10.3%, respectively). In terms of glucose metabolism, HIIT improves insulin sensitivity and β-cell function. The lipid profile also improves through the lowering triglyceride by 13%, increasing of high-density lipoprotein by 25%, and lowering low-density lipoprotein by 9% in the HIIT group but not in MICT. Both types of exercise reduces blood pressure by approimately 10 mm Hg systolic and 6 mm Hg diastolic. HIIT was also reported to be more enjoyable than MICT and improves the quality of life. The study shows that there is no adverse event that complies with both HIIT and MICT.

How did the researchers interpret the results?
The researchers’ interpretation was that HIIT has beneficial impacts on cardiometabolic diseases. HIIT has superior improvement on some cardiometabolic risks (such as VO2 max, glucose metabolism, and serum lipid) or at least equal improvement on blood pressure compared with MICT. Although both types of training methods have similar benefits, HIIT is performed in a shorter period of time and is therefore a more time efficient option of exercise. HIIT can also be a safe option of exercise for improving cardiometabolic diseases.

The quality of evidence for this study is commendable, however there are methodological limitations, such as the small sample sizes (total 10 articles that involved 273 patients). The future study should include bigger sample sizes to decrease the bias of the publication.

What conclusions should be taken away from this research?
The research concludes that HIIT has greater or at least equal benefits compared with MICT towards improving cardiometabolic diseases. HIIT may become a safe and more time efficient option of exercise that may give benefits on improving cardiometabolic diseases.

What are the implications of this research?
This study gives evidence on the public health guideline. Incorporating HIIT into rehabilitation programs may be more achievable for people with cardiometabolic diseases. This allows them to reach a level of exercise that may enhance health benefits. Although the study suggests that the adverse event of doing HIIT is low, the protocol recommendation for HIIT program (Table 1) is essential to be developed. The development of this protocol is to ensure that HIIT is safe for high risk participants (i.e people with cardiometabolic diseases), because, some health professionals argue that angina episodes can be triggered by high intensity exercise. Future studies should investigate whether or not this aprroach is sustainable for non-supervised individuals who are performing HIIT in home-based environments. '''Table 1. Protocol Recommendation for HIIT'''