Twenty-four all-out sprints of just five seconds each burned about 209 calories in a single session, roughly the energy cost of a 20-minute moderate jog, according to researchers at Wilfrid Laurier University. The whole workout, including warm-up and recovery, lasted around 18 minutes, but the actual sprinting added up to only two minutes.
The finding comes from a pair of studies by Tom Hazell, a professor in the Department of Kinesiology and Physical Education at Wilfrid Laurier, and colleagues, published in Applied Physiology, Nutrition, and Metabolism in 2017. Nine recreationally active men tried three sprint interval training protocols, each with the same total of two minutes of sprinting.
Shorter sprints, more of them
The classic protocol used four 30-second sprints with four minutes of rest in between. The modified versions broke the same two minutes into eight 15-second sprints with two-minute recoveries, or 24 five-second sprints with 40-second recoveries. All three sessions ran 18 minutes end to end.
Energy expenditure during the 24-sprint version reached 209 kilocalories, compared with 163 for the eight-sprint version and 138 for the classic four-sprint version. That is a 52 percent increase in calories over the traditional protocol, even though total sprinting time was identical.
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Participants also found the shorter bursts easier to tolerate. Their pleasure ratings had returned to close to pre-exercise levels within 30 minutes of finishing, and they reported stronger intentions to do the workout again.
Why brief sprints punch above their weight
Part of the calorie cost of a sprint session shows up after you stop moving. Excess post-exercise oxygen consumption, often shortened to EPOC, is the extra oxygen your body uses to return to a resting state.
According to the American Council on Exercise, EPOC is driven mainly by intensity rather than duration, and the afterburn from a high-intensity interval workout can add 6 to 15 percent of the session's total energy cost. Because all-out sprints tap anaerobic energy stores hard, the body has more replenishing to do once the work ends.
Sprints versus HIIT in a broader comparison
A separate analysis by RunRepeat compared sprint interval training with longer high-intensity interval training and steady moderate-intensity exercise. On body fat percentage, sprint interval training produced about 39.95 percent greater reductions than HIIT, while participants spent about 60.84 percent less time exercising.
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A cautious way to try it
A simple beginner-friendly session might look like a five-minute easy jog or bike warm-up, eight rounds of 10-second all-out sprints with 50 to 60 seconds of easy pedaling or walking between them, and a five-minute cool-down. The total sits close to 15 minutes.
Sprint work is high-impact and demanding on joints, tendons and the cardiovascular system. Anyone new to exercise, returning after a break, managing heart disease, high blood pressure or joint injuries should talk to a doctor before adding all-out efforts. A stationary bike or a hill sprint is often gentler on the knees than flat-out running on pavement.
There is also research suggesting that three minutes of hard sprinting can move blood markers in a way that a longer easy jog does not, another sign that intensity, not just duration, drives many of the benefits attributed to cardio.
The Hazell study was small, nine participants and all male, so the exact numbers should be read as a signal rather than a settled fitness prescription.
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What it does line up with is a broader body of interval research suggesting that a few minutes of genuine all-out effort, done more than once a week, can deliver a calorie and fat-loss return that longer moderate sessions struggle to match in the same clock time.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.