High-intensity Interval Training for Health and Fitness: Can Less Be More?
Glenn A. Gaesser and Siddhartha S. Angadi.
Traditionally, the form of exercise most commonly prescribed by clinicians is continuous moderate-to-vigorous-intensity exercise that can be sustained for 20–60 min. This is consistent with current US public health guidelines recommending that adults accumulate at least 150 min/wk of moderate-intensity physical activity or 75 min/wk of vigorous-intensity physical activity.
The percentage of US adults meeting these minimal guidelines is extremely low. Among the many reasons for not exercising is a “perceived lack of time,” which is one of the most frequently cited barriers.
As little as 30 min of vigorous exercise per week, within a total exercise time commitment of 75 min/wk, improved glucose control and markers of skeletal muscle metabolism in patients with type 2 diabetes.
Over 2 wk, eight subjects completed six high-intensity interval exercise sessions,with each session consisting of 10 60-s bouts on a leg cycle ergometer that elicited 90% maximal heart rate (HRmax), interspersed with 1:00 of rest. .Albeit just a pilot study on eight subjects, the results are consistent with a number of publications within the last few years that demonstrate the benefits of HIIT.
Low-volume HIIT typically consists of several bouts of high-intensity exercise lasting between 1 and 4 min, which elicit 85–95% of HRmax and/or VO2max, interspersed with bouts of rest or active recovery).
Some versions of HIIT involve much shorter exercise intervals, lasting only :08, with up to 60 repetitions in a single exercise session.
In general, HIIT involves only 8–16 min of actual “on time” for vigorous-intensity exercise, with the total workout, including warm up, cool-down, and rest/active recovery periods, requiring only 20–25 minutes.
In the few investigations that have addressed HIIT, subjects appear to not only tolerate the higher exercise intensity, they actually prefer HIIT to the moretraditional steady-state continuous exercise. In young healthy males, it was reported that ratings of perceived “enjoyment” were higher for HIIT than for steady-state continuous exercise, despite RPE being higher for HIIT. Similarly,patients with heart failure found HIIT more motivating than traditional steady-state exercise, which was perceived as “quite boring.”
Recent epidemiological evidence from the Norwegian HUNT study indicated that just a single weekly bout of high-intensity exercise was found to reduce the risk of cardiovascular disease in both men and women (relative risk: 0.61 and 0.49, respectively).
With such a large percentage of the US population failing to meet even minimum physical activity guidelines, HIIT may help insufficiently active individuals overcome a major barrier to maintaining a physically active lifestyle, that of a perceived lack of time. An added bonus is that from a time-benefitperspective, HIIT may prove to be a good example where less can be more.