Horizon: The Truth About Exercise, BBC Two, review Are you sitting comfortably? Well, you shouldn't be. If there's one thing that last night's Horizon: The Truth About Exercise (BBC Two) made abundantly clear, it is that sitting comfortably is errant madness. The chair is a killer. Stand up right now and give yourself a thwack with a ruler. Give your chair a thwack too, for good measure. Of course, it wasn't chairs per se that were being blamed by the documentary for making everyone fat. It's our propensity to sit on them and not move about that is turning us in to gunky-arteried blimps. And if all of this is sounding like stuff you probably could have guessed yourself well, that was the problem with The Truth About Exercise. Because as so often with science documentaries that promise to slay sacred, in this case fatted, cows, what presenter Michael Mosley had to tell us wasn't all that revelatory. The chair thing, for example, was another way of saying that sitting around all day is bad. Moving about a lot is good. The truth about exercise, therefore, is that it is good for you. Well, duh! But if most of what Mosley had to astound us with was really not that astounding, one little gobbet was: you can, according to a growing body of research, do a lot of good by hitting yourself. Put down that paddle, man - "Hit," in this case, is an acronym that stands for "High Intensity Training," and Hit is the buzzword that should have every gym, sports shop and personal trainer in the country quivering in their lycra track pants. It suggests that you can gain an awful lot by doing very little: three 20-second bursts of near-delirium, three times a week, or a grand total of three minutes" exercise. That is roughly half as long as it takes me to find my gym kit. In order to test the theory, Mosley played guinea pig. The metaphor was an apt one as after 20 seconds going berserk on an exercise bike he was indeed making some noises like a tubercular rodent. But he came back after one month of Hit and both his insulin sensitivity and his aerobic fitness were vastly improved. As these are two things that are likely to make you live longer, Hit, in his case, was a hit. The "in his case" is important, alas, as the programme's other message was that what works for some people doesn't work for others. If you are really lucky, a quick DNA test could prove you to be "a fitness non-responder." This is like a hereditary lifelong off-games chit. Sheer bliss. So the health advice varied between quite diverting and rather predictable, but as television it was like 40 minutes on a treadmill, which is to say dull. Essentially, Mosley could have done with transferring his exercise advice to his own programme-making. Longer isn't necessarily better - he could have summarised the entire programme in three 20-second bursts, delivered three times. That way we wouldn't have had to sit down for so long and watch it, all the while being quietly killed by our chairs and sofas.