Fit in four minutes. It sounds like a headline from a health magazine; an unattainable promise on late-night satellite TV. Then you attempt Dr Izumi Tabata’s training protocol – 20 seconds of all-out effort, 10 seconds of rest, repeat eight times – and between sounding like Darth Vader as you desperately suck in oxygen and collapsing in a messy bundle of sweat and defeat, you realize just how wrong you were. Tabata has seen it all before. “They were dead!” he chuckles as he recalls the first time he inflicted the system that bears his name on his university students in the early 1990s. “After four minutes’ hard exercise they were wiped out. But after six weeks they saw the results and were surprised. We all were.” His research followed extensive monitoring of Japan’s speed skating team in the early 1990s when he – along with the team’s coach Irisawa Koichi – noticed that short bursts of brutally hard exercise seemed to be at least as effective as hours of moderate training. Tabata set out to show this with a simple experiment. One group of moderately trained students performed an hour of steady cardiovascular exercise on a stationary bike five times a week. The other group did a ten-minute warm-up on the bike, followed by four minutes of Tabata intervals, four times a week – plus one 30-minute session of steady exercise with two minutes of