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For patient populations with low V̇ o 2max (e.g., <20 ml It should be emphasized, however, that the exercise load imposed in HIIT is relative to the individual's own aerobic capacity. Large, multicenter trials using the HIIT paradigm have been advocated ( 5). Safety of HIIT, particularly for high-risk patient populations, needs to be established. Similarly, patients with heart failure found HIIT more motivating than traditional steady-state exercise, which was perceived as “quite boring” ( 13). ( 1) reported that ratings of perceived “enjoyment” were higher for HIIT than for steady-state continuous exercise, despite RPE being higher for HIIT. In fact, in the few investigations that have addressed this issue, subjects appear to not only tolerate the higher exercise intensity, they actually prefer HIIT to the more traditional steady-state continuous exercise ( 1, 13). This protocol elicited ratings of perceived exertion (RPE) of only ∼4–8 on a 10-point scale, suggesting that this HIIT paradigm may have clinical utility. Subsequently, this group modified their HIIT protocol to the less intense 10 × 60-s interval version used in the current paper. Gibala and McGee ( 2) initially introduced an “extreme” version of HIIT, using 4–6 “all-out” Wingate tests as the exercise stressor ( 2). 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 min ( 1, 2, 4– 10, 13). Some versions of HIIT involve much shorter exercise intervals, lasting only 8 s, with up to 60 repetitions in a single exercise session ( 9). Low-volume HIIT typically consists of several bouts of high-intensity exercise lasting between 1 and 4 min, which elicit ∼85–95% of HR max and/or V̇ o 2max, interspersed with bouts of rest or active recovery ( 2, 5). HIIT has also been reported to be more effective than continuous, steady-state exercise training for inducing fat loss in men and women, despite considerably less total energy expenditure required during training sessions ( 9, 10). Greater improvements in V̇ o 2max may positively impact longevity prospects in the general population and in patients with cardiometabolic diseases (see Refs. Although many outcome measures (e.g., blood pressure) can be improved independently of exercise training intensity ( 5) and the documented health benefits of moderate-intensity exercise provide the scientific basis for current physical activity guidelines, HIIT has been shown to be more effective than moderate-intensity continuous exercise training for improving endothelial function and reversing left ventricular remodeling in patients with heart failure ( 13), for reducing central body fat and fasting plasma insulin in young women ( 9), and for improving maximal oxygen uptake (V̇ o 2max) in subjects with metabolic syndrome ( 8), heart failure ( 13), and coronary artery disease (CAD 7).

are consistent with a number of publications within the last few years that demonstrate the benefits of HIIT ( 2, 4, 5, 8, 9, 13). Several muscle mitochondrial proteins were increased by ∼20–70%, and glucose transporter 4 protein levels were raised by 369%.Īlbeit just a pilot study on eight subjects, the results of Little et al. Average 24-h blood glucose was reduced by 13% and postprandial blood glucose by 30%. 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 (HR max), interspersed with 60 s of rest. ( 6) report that 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. In this issue of the Journal of Applied Physiology, Little et al. Recent research on the benefits and efficacy of low-volume, high-intensity interval training (HIIT) may help to overcome that barrier. Among the many reasons for not exercising is a “perceived lack of time,” which is one of the most frequently cited barriers ( 3). Despite the well documented health benefits of regular physical activity and the persistent public health messages for Americans to become more active, the percentage of US adults meeting these minimal guidelines is extremely low ( 11).

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. 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.

Exercise is an established therapeutic adjunct in the management of several chronic diseases.