High intensity interval training (HIIT) of under 15 minutes – inclusive of warm up and cool down – yields comparable improvements to interventions meeting the current World Health Organisation guidelines that are unattainable for many, finds an Australian study.
The current WHO physical activity guidelines (150-300 min of moderate activity/week or 75-100min of vigorous activity/week) may be unachievable for a large portion of the population who are time poor due to family or work commitments. This hypothesis is supported by the increasing rates of physical inactivity amongst adults in high income countries.
The researchers defined low-volume HIIT as interventions which included less than 15 minutes of high intensity exercise per session (not including recovery periods).
This review builds on the authors' recent study which showed that as little as 4-min of HIIT 3 times per week for 12 weeks significantly improved blood sugar levels, fat in the liver, and cardiorespiratory fitness in adults with type 2 diabetes. They also showed that these improvements were comparable to an intervention involving 45-min of moderate intensity aerobic exercise.
Beyond its effect on metabolic health, the new review reported that low-volume HIIT can also improve heart function and arterial health. The research was performed by collating and critically appraising over a decade's worth of research on the topic.
Further research should explore whether low-volume HIIT is sustainable in the longer-term and whether combining low-volume HIIT with other training interventions, such as resistance training, can maximise health outcomes.
Dr Angelo Sabag, corresponding author of the study said: "While the WHO guidelines may serve their purpose at a populational level, individualised and tailored low-volume HIIT interventions delivered by appropriately trained exercise professionals may be more effective at an individual level, especially for time-poor individuals. This research is especially important now as people are looking for new and exciting ways to engage in regular exercise, after a year of lower physical activity due to the pandemic."
Low‐volume high‐intensity interval training for cardiometabolic health
Angelo Sabag, Johnathan P Little, Nathan A Johnson
Published in The Journal of Physiology on 24 March 2021
High‐intensity interval training (HIIT) is characterised by short bouts of high‐intensity submaximal exercise interspersed with rest periods. Low‐volume HIIT, typically involving less than 15 min of high‐intensity exercise per session, is being increasingly investigated in healthy and clinical populations due to its time‐efficient nature and purported health benefits. The findings from recent trials suggest that low‐volume HIIT can induce similar, and at times greater, improvements in cardiorespiratory fitness, glucose control, blood pressure, and cardiac function when compared to more traditional forms of aerobic exercise training including high‐volume HIIT and moderate intensity continuous training, despite requiring less time commitment and lower energy expenditure. Although further studies are required to elucidate the precise mechanisms of action, metabolic improvements appear to be driven, in part, by enhanced mitochondrial function and insulin sensitivity, whereas certain cardiovascular improvements are linked to increased left ventricular function as well as greater central and peripheral arterial compliance. Beyond the purported health benefits, low‐volume HIIT appears to be safe and well‐tolerated in adults, with high rates of reported exercise adherence and low adverse effects.
See also MedicalBrief archives: