A few relatively short bursts of intense exercise, amounting to only a few minutes a week, can deliver many of the health and fitness benefits of hours of conventional exercise, according to new research. This apparently outrageous claim is supported by many years of research done in a number of different countries. [Welcome to] the world of High Intensity Training (HIT). By doing just three minutes of HIT a week for four weeks, [you can] expect to see significant changes in a number of important health indices. But how much benefit you get ... may well depend on your genes. The fact is that people respond to exercise in very different ways. In one international study 1,000 people were asked to exercise four hours a week for 20 weeks. The results were striking. Although 15% of people made huge strides ... 20% showed no real improvement at all. The exercise they were doing was not making them any aerobically fitter. [HIT is] actually very simple. You get on an exercise bike, warm up by doing gentle cycling for a couple of minutes, then go flat out for 20 seconds. A couple of minutes to catch your breath, then another 20 seconds at full throttle. Another couple of minutes gentle cycling, then a final 20 seconds going hell for leather. And that's it. Active exercise ... seems to be needed to break down the body's stores of glucose, deposited in your muscles as a substance called glycogen. Smash up these glycogen stores and you create room for more glucose to be sucked out of the blood and stored. Like any new exercise regime if you have a pre-existing medical condition you should consult your doctor before trying it.