Active Voice: Adherence to HIIT in Free-Living Conditions – Mounting Evidence of Its Potential as a Viable Exercise Option
By Mary E. Jung, Ph.D., and Sean R. Locke, Ph.D.
Mary Jung, Ph.D., is an associate professor in the School of Health and Exercise Sciences at the University of British Columbia (UBC), Okanagan Campus in Kelowna, BC. Dr. Jung is a Michael Smith Foundation for Health research scholar and a Canadian Institutes of Health Research Early Career Foundation grant recipient. Her overarching research interests lie in self-regulation of health behaviors, with focus on exercise adherence for the prevention of Type 2 diabetes. She directs the Diabetes Prevention Research Group at UBC Okanagan. Dr. Jung also is a member of ACSM.
Sean Locke, Ph.D., is a postdoctoral fellow in the School of Health and Exercise Sciences at the University of British Columbia, Okanagan Campus. Dr. Locke is a Diabetes Canada postdoctoral fellow and Michael Smith Foundation for Health research postdoctoral fellow recipient. His research broadly examines techniques for optimizing health behavior interventions. More specifically, he examines counseling methods for modifying the unhelpful lens through which some view diet and exercise.
This commentary presents Dr. Jung’s and Dr. Locke’s views on the topic of the research article they co-authored with other colleagues. Their article appeared in the October 2018 issue of Medicine & Science in Sports & Exercise® (MSSE). There’s no denying that Type 2 diabetes (T2D) is a global epidemic associated with tremendous societal, economic and personal costs. Significant efforts are being made to identify individuals at high risk of T2D and mitigate that risk. Regular physical activity, along with a healthy diet, have been shown to prevent or delay the onset of T2D, yet very few adults maintain enough regular physical activity to reduce the risk of developing T2D.
High-intensity interval training (HIIT) has consistently been shown to lead to cardiometabolic improvements that are equal to, if not superior to, results achieved through moderate-intensity continuous training (MICT). Thus, HIIT may be a viable option for T2D risk reduction. Despite the appealing time-efficient nature of HIIT and the associated positive health adaptations, the utilization of HIIT as a public health strategy is not without its critics. Opponents argue that HIIT is inappropriate for adults who are sedentary or those at increased risk of chronic disease. In addition, some opponents criticize HIIT for being too intense and leading individuals to feelings of negative affect that will undermine competence and adherence.
However, recent research has cast doubt on critics’ arguments. For example, inactive adults have reported comparable exercise enjoyment and confidence about their willingness to engage in both HIIT and MICT after completing a single bout of HIIT. A recent scoping review comparing HIIT and MICT also has concluded that HIIT is a viable exercise option.
HIIT, in short, is repeated bouts of vigorous intensity exercise separated by periods of active recovery at low intensities. HIIT can be performed without specialized equipment and does not require extensive recovery between intervals. Home-based prescriptions are simple to remember and administer, e.g., “one-minute on, one-minute off” or “power walk to the lamppost, then walk casually to the next lamppost.”
The primary purpose of our study, as described in the October 2018 issue of MSSE, was to pilot test the Small Steps for Big Changes intervention framework for lowering T2D risk factors. Our aim was to examine the impact of HIIT versus MICT for promoting physical activity adherence 24 weeks following the exercise intervention. We hypothesized that exposure to HIIT would lead to greater objectively measured moderate-to-vigorous physical activity (MVPA) behavior 24-weeks post-intervention, when compared to MICT. A secondary purpose was to examine the differential impact of engaging in HIIT or MICT on cardiorespiratory fitness and psychosocial outcomes.
We randomized 32 low-active adults at elevated risk for developing T2D to HIIT (n=15) or MICT (n=17) conditions. The brief, low-cost intervention consisted of seven exercise sessions accompanied by 10 minutes of counseling at each supervised session, over a two-week period. We designed the counseling sessions to leverage the power of evidence-based behavior- change techniques known to promote physical activity engagement and self-management in this population.
Twenty-four weeks following the two-week intervention, those randomized to HIIT increased their MVPA by 53 minutes compared to an increase of 19 minutes for those in MICT. Greater increases in cardiorespiratory fitness were observed for those in the HIIT group. Both groups increased their self-efficacy to engage in and manage their exercise following the intervention; however, these levels returned to baseline 24 weeks later.
The magnitude of effects observed in this study provide enough justification for conducting a fully powered randomized control trial with a long-term follow-up period to examine the impact of the Small Steps for Big Changes intervention on clinically meaningful endpoints for T2D risk reduction, e.g., HbA1c.
This study adds to the mounting evidence suggesting that individuals can and do adhere to HIIT, making it a viable option for disease prevention and health promotion.