THE FASHION world often forgets to pay homage to the people who make sportswear. Yet sportswear has increasingly set the pace for fashion, particularly on the high street, where leggings, trainers, Lycra shorts and shellsuits all trace their origins back to the sports field. One reason for this evolution is the advance made by sports manufacturers in clothes technology, from waterproof mountaineering jackets to air- cushioned soles and super-stretch swimsuits.

The latest innovation from these sartorial poor-relations is a new generation of 'breathable' fabrics which has given added versatility to all-weather jackets. While many of these fabrics have been available for years, manufacturers have only recently worked out the best ways of incorporating them in clothing.

Fabrics such as Gore-Tex, made by W L Gore, and Sympatex, by Akzo, are called breathable because they allow perspiration to evaporate through the material so you don't get too clammy. Old-style nylon anoraks now look very inadequate. The new fabrics are also waterproof and windproof and lightweight, which is why mountaineers, skiers and hill-walkers swear by them.

Not that sports clothing is any easier to buy than other forms of clothing. There are still rather too many coats and jackets in the shops, adorned with swing-tickets making extravagant claims but which provide inadequate protection in extreme conditions. Don't be swayed by the allure of bright colours and soft-touch fabrics. If in doubt, buy from specialist retailers who will give you sound advice.

Berghaus, a British company, is one of the more reliable brands. Its thin, lightweight jackets have a membrane between the surface fabric and inner lining made from Gore-Tex.

The details of a jacket's construction are as important as the fabric. Gina George, senior sportswear buyer at Lillywhite's of Piccadilly Circus, points out that the seams on a Berghaus jacket are taped to seal the Gore-Tex membrane throughout. A good-quality mountaineering and skiing jacket should have covered zips with tags on them so that you can open them without removing your gloves, she says. The hood also needs to be right. The Berghaus hood has a stiffened rim so that you can fix it close around your face, and toggles to draw it close.

Snow & Rock, a specialist retailer with branches in London and Birmingham, imports some of the most impressive brands from North America. Mark Fallon of the store's climbing department recommends the Alpinist jacket from Marmot, which has reinforced shoulders, a generous cut and pit zips - under-arm zips for extra ventilation.

The North Face Mountain jacket is another classic, made by a Californian company much respected by mountaineers. These are probably rather more advanced than the average walker needs, but the technical details are fun even if you have no intention of climbing in the Himalayas.

Besides, there is plenty of overlapping between sportswear and casual wear in modern fashion. Ski jackets or Henri-Lloyd sailing jackets no longer look out of place on the high street in winter.

Another American product recommended for trekking and mountain walking is Patagonia's Nitro jacket, a longer, well- cut jacket with a detachable hood. Its H2 No Storm fabric has similar properties to those of Gore-Tex and Sympatex.

The jacket alone is never enough. The ideal outdoor wardrobe should consist of several layers of clothing. Richard Furlong, a keen amateur climber, says: 'I wear layers because it's a flexible, adjustable way to dress. If I'm climbing in the Alps, it might be freezing when we set off in the morning. After an hour, I take off a layer. By mid-day, I might be down to a vest if the sun is hot.'

Furlong makes the point that the layers must be light. Modern mountaineers have no room for traditional bulky woollen sweaters. Berghaus makes lightweight Polartec tops from a soft double- faced pile which dries quickly and keeps the wearer very warm. Also recommended for both warmth and lightness is the range of Synchilla jackets from Patagonia.

Many manufacturers and retailers devise their own 'systems' of dressing, which impress customers because they sound terribly technical. In truth, they all work on the same premise of layers of clothing for maximum comfort.

The 'system' developed by Rohan, a British company, typically includes a Gore-Tex waterproof jacket combined with a fleece underjacket, a winterweight shirt and a roll-neck thermal top.

The three most important layers are: the thermal garments worn close to the skin which draw away perspiration; the layer of fleece which provides insulation; and the jacket on top to keep out the wind, rain and snow.

Many of the new jackets combine two or more layers in one. Columbia Sportswear, a leading American brand for skiers and walkers, call it their 'interchange system': a lightweight outer shell and a zip-in fleece liner which can be worn separately or together to suit the weather conditions.

Few of these jackets come cheap, but the manufacturers offer guarantees that they will last a good while. They represent a sound investment for anyone who spends time in the great outdoors.

(Photographs omitted)