Researchers wanted to know if super-short bursts of intense exercise did any good.
So they made people sit for six hours straight, then put them on a stationary bike. They made them pedal as hard as they could for four seconds, followed by a 45-second break, and they repeated that process five times. Each person did it once an hour, for eight hours throughout the day. Which might sound like a lot. But all total, that's only 2 minutes and 40 seconds of actual exercise a day. And it made a significant difference in their health within 24 hours.
When doctors tested their blood the next day, their triglycerides were 30% lower than the day before. And their metabolism had jumped, so they were burning more calories even when they were doing nothing. The study used bikes, but evidently any sort of high-intensity exercise could work. If so, even a few sets of jumping jacks once an hour could make a big difference.