Ski racing just for the outing

This Saturday may mark the apex of the let's-chase-each-other-across-the-snowy-tundra season. We speak specifically of three noteworthy mass-start cross-country spectaculars and of the popular citizen race phenomenon in general.

One of Saturday's extravaganzas is mostly uphill, one is mostly downhill, and one more or less on the level. Two are in New England, one in Wisconsin; but they could be just about anywhere there is snow in this world. That's how much success cross-country ski racing-rallies have gained.

The uphill grind is the fourth annual ascent of Mt. Greylock, about a 31/2 -mile pull up the Massachusetts Berkshires' tallest peak (3,491 feet), followed by what can be a blazing seven-mile descent.

At Stowe, Vt., it's all downhill when they start the ''oldest annual downhill cross-country ski race in the country.'' The 10-mile run (from the top of Mt. Mansfield's single chair down the Toll Road, dropping 2,500 feet in 41/2 miles, then through fields and forest to the finish on Main Street) began in 1945 as a challenge between four US ski pioneers, including Stowe developer Sepp Ruschp and mountaineer Erling Strom.

By far the biggest citizen race in the United States is the American Birkebeiner, in its 10th year at Telemark, Wis. It is one of a series of international citizen-racer ski marathons.

Some 6,000 skiers may participate and 100 media representatives cover the 55 -kilometer marathon. A mere 27.5-km ''korteloppet'' is held for the sprinters.

The nice thing about these ''citizen'' happenings is that people do them for all kinds of reasons, including just enjoying the view and maybe even a picnic. The competition-oriented lead the pack, and many of the others are glad to let them. It's one of the best ways yet devised to enjoy the excitement of a race without getting caught up in ''how well did I do?''