Such training, known as HIIT, typically involves short bursts of high-intensity exercise followed by a short period of rest or recovery: intermittently sprinting for 30 seconds, for example, during a moderate-pace jog.

The US national physical activity guidelines recommend 150 minutes of moderate activity or 75 minutes of vigorous activity each week with additional muscle-strengthening exercise for adults and 60 minutes a day for children, noted Walter R. Thompson, author of the report and prtesident of the American College of Sports Medicine. “So if you step it up a little bit and get your heart rate up and move from, say, walking to jogging, it decreases to 75 minutes per week.”