Anyone who thinks that coming up with a new sports bra is simply a matter of slinging together a few bits of elastic and Lycra would do well to consider the rigorous research that led to the Berlei Shock Absorber range. A group of brave volunteers with varying bust and cup sizes were persuaded to run on a treadmill at varying speeds, first wearing no bra, then wearing an ordinary bra and then a sports bra. A team of dedicated scientists videoed their efforts, in order to calculate exactly how much jiggling was going on. Braless, and running at top speed, breasts were bouncing as much as 8.5 centimetres out of kilter - a highly undesirable effect that will eventually mean a permanent droop. (You could try jumping up and down in front of the bedroom mirror armed with a ruler if you want to know what your own bosoms are doing when you jog, though this kind of experiment is probably best left to the professional boffin.) Berlei also roped in the Olympic runner Sally Gunnell as a style consultant. "I don't want an Army Issue bra," she told them firmly. (The Army deny that there is any such thing, possibly for reasons of national security.) Depending on whether your idea of a workout is a gentle cycle round the block or a sprint marathon, and also on how voluptuous you are, you may need an Impact Level 1, 2 or 3 Shock Absorber. All this sounds rather daunting, as if they are expecting you to crash into things at speed. But the bras themselves are excellent. Wearing one is like being clasped, firmly but pleasantly, across the chest. Nothing moves at all, and I mean nothing. There is not a quiver, a jiggle, a bounce or a ripple. This is serious bosom discipline. The combined crop-top and bra style is designed to be worn on its own, though its firm hold tends to mean that midriff flab is thrown into unsightly rolls (presumably persevering in the kind of activities you need to wear the top for will eventually mean you can wear it on the street without frightening the neighbours). Sally Gunnell appears in action on the boxes, which makes the wearer hopeful that somehow, miraculously, simply putting on the bra will turn her into an Olympic athlete. Of course it doesn't work quite like that, though seeing how your Shock Absorber would look on a toned and muscled torso could be taken as an inspiration (or could send you into total despair). There are also matching Shock Absorber knickers: if only they controlled the bottom in the same way!

The Shock Absorber Impact Levels 1-3 is available from major department stores and specialist sports shops; prices start at pounds 16.99. For your nearest stockist, ring 01525 850088