6 Reasons to Make HIIT Workouts Part of Your Weekly Routine
Weekly physical activity guidelines recommend doing 150-300 minutes of moderate-intensity aerobic exercise or 75-150 minutes of vigorous cardio.
300 minutes of moderate-intensity cardio per week (43 minutes per day) may be the minimal dose to offset hypertension risk.
15 minutes of high-intensity interval training (HIIT) may have similar health benefits to 45 minutes of moderate-intensity aerobic exercise.
University of California, San Francisco researchers recently published a 30-year study (Nagata et al., 2021) which found that adhering to the minimum weekly guidelines of 150 minutes (2.5 hours) of moderate-intensity physical activity per week wasn't enough to offset the risk of developing hypertension in midlife.
The UCSF researchers speculate that men and women in their 20s, 30s, 40s, and 50s should aim for at least 300 minutes (5 hours) of moderate exercise per week to keep blood pressure low. The main takeaway from this decades-long study is that at least 43 minutes of moderate-intensity cardio a day may be the minimal dose to "keep the doctor away" as we age.
45 Minutes of Moderate-Intensity Cardio vs. 15 Minutes of HIIT
Another recently published paper (Sabag, Little, & Johnson, 2021) reviews a decade's worth of research into the cardiometabolic benefits of low-volume, high-intensity interval training (HIIT). This topical review was published on March 21 in The Journal of Physiology.
What are short bouts of HIIT? Low-volume HIIT workouts generally take less than 20 minutes total, which involves a warm-up/cool-down period plus anywhere from 4 to 15 minutes of high-intensity exercise per session (not including recovery periods).
The latest review of low-volume HIIT research suggests that short bouts of vigorous exercise interspersed with brief intervals of low-intensity recovery "yields comparable improvements to interventions meeting the current guidelines [of moderate-intensity exercise] despite requiring significantly less time."
"[Our] 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," the authors write in their paper's abstract.
"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," they add.
Six Ways 15-Minute HIIT Workouts Improve Cardiometabolic Health
Cardiorespiratory fitness
Heart function
Arterial health
Blood pressure
Glucose control
Liver fat
Taken together, this topical review of over ten years of research into low-volume HIIT suggests that the improvements to cardiometabolic health from short, high-intensity interval training cardio sessions is "comparable to an intervention involving 45-min of [continuous] moderate-intensity aerobic exercise."
Low-volume aerobic exercise interventions may be especially helpful for people with type 2 diabetes. A study from last year (Sabag et al., 2020) published in Diabetes Care suggests that doing as little as 4 minutes of HIIT (three times a week for 12 weeks) significantly improved cardiorespiratory fitness, fat in the liver, and blood sugar levels in adults with type 2 diabetes.
"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," co-author Angelo Sabag said in an April 15 news release. "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."
Although Sabag, Little, and Johnson say "the overwhelming majority of available evidence shows that low-volume HIIT is a safe way to exercise, including in populations with metabolic and heart problems," they also strongly recommend that "individuals should always determine their individual suitability for such programs with their health care professional."
DISCLAIMER: This blog post is not intended as medical advice. Please use common sense and always consult with your doctor before incorporating HIIT workouts into your weekly routine—especially if you haven't done high-intensity aerobic exercise in recent months.