The Boston Celtics hope that the `sweat equity' from pre-season workouts will pay off next June in their second straight NBA title.

THE re-greening of the Boston Celtics has begun. Pro basketball's reigning champions have laced up their trademark black sneakers and convened training camp on the secluded campus of Hellenic College in suburban Brookline.

The situation is strikingly different from that on Celtics Pride Day last June, when Larry Bird and his teammates stood on a city hall balcony and surveyed nearly a quarter-million cheering fans.

For the moment, no one applauds when Bird swoops to the basket in a virtually empty gym. The ``men at work'' sign is out, and the time for living off memories is over.

Thoughts of last season, when the Celtics beat the Houston Rockets to secure their 16th National Basketball Association title, are replaced by a growing preoccupation with the task at hand -- how to become the first NBA team since the 1968-69 Celtics to win back-to-back championships.

``The summer could have lasted longer as far as I'm concerned,'' says Celtics center Robert Parish. Even so, a restlessness set in at the end of August, telling him that training camp was approaching and prompting a pattern of early risings. ``I don't need an alarm clock anymore,'' he intones in his rich bass voice.

Of course Parish and his mates aren't exactly asked to fall out of bunks to a predawn reveille. The players live at home and commute to practices, which start at 10 a.m. They arrive earlier, though, to allow time to get their ankles taped. Sopping jerseys and T-shirts

Celtics coach K.C. Jones would never be accused of running a soft camp; the sopping practice jerseys and T-shirts attest to that. On the other hand, he's what might be called an enlightened drill instructor, a guy with a firm grip covered with a velvet glove.

``K.C. is a little different from most coaches,'' Bird explains. ``He just kind of stands back and tells you what he wants done, and you do it, and he goes on to the next thing. He knows what it takes to get us in shape. He don't work us real hard, he just works us to a point where we can play our way into shape.''

Bird feels this is the ideal approach for a veteran unit like the Celtics, who must avoid peaking too early in a season that begins Oct. 31 and runs to nearly 100 games when the playoffs are included. Brushing up the basics

This year's camp is unique in that it includes just one newcomer, Fred Roberts, rather than the handful of rookies and free agents who normally vie for jobs. Roberts, whose beard and flattop haircut look somewhat out of place, was acquired in a trade with the Utah Jazz. If he makes the club, he will back up Bird and Kevin McHale at the forward spots, an assignment that top draft choice Len Bias was expected to handle before his drug-related death.

With a streamlined, rookie-less roster, the Celtics have only had to brush up the basics. The emphasis has been on conditioning, learning an offense and defense, and working on special situations -- 3-point plays, 5-second plays, out-of-bounds plays, and the like.

``Once the gate opens,'' Jones says, ``the coach should be able to sit back and feel everything's been taken care of. All you want to do after that is make minor adjustments.''

NBA camps generally attract far less attention than those in baseball and football, in part because they are more low key and compete for the spotlight during the baseball championships and football season. That, however, didn't stop the Celtics from luring a large contingent of writers and broadcasters to the recent Media Day, which officially marked the opening of practice.

It was an opportunity for conducting interviews, getting mug shots, and even some autograph seeking on the side.

Then comes the most grinding period of the camp, the twice-a-day sessions that occupy the first week. A standard practice begins with loosening-up exercises, in which players seem to lounge more than strain on the freshly refinished court. From there, the pace picks up with fast-break and shooting drills sandwiched around scrimmages.

Jones and his three assistant coaches may walk the team through several plays; then the players run through them as guard Dennis Johnson calls out such cues as ``Motion'' or ``One up.''

Only the squeaking of sneakers and good-humored interplay among teammates breaks the library-like silence of these private sessions, which are open to a chosen few, including friends of legendary team president Red Auerbach, who sits in a folding chair at courtside.

The logic of all the movement can escape even the most-seasoned journalist. Asked what he had learned from 10 years of watching these practice sessions, one ``beat'' writer confessed, ``Not much. It's too complex.''

The Celtics used to hold preseason workouts at the Massachusetts Maritime Academy in Buzzards Bay, on Cape Cod. Shirt-to-shirt basketball

But that was too far from Boston, and about a decade ago the team moved to Hellenic College, a tiny school with a Greek Orthodox affiliation. The school's immaculate, but modest, gym makes an ideal practice home -- quiet, convenient, and pleasantly tucked away in a wooded residential area.

Unpretentious would be an apt description. Rollaway bleachers line one side of the court, a stage the other. To protect players from crashing into the concrete-block walls at each end, tumbling pads are hung under the baskets.

The environment is not necessarily what you'd expect of basketball's premier franchise. ``I thought the gym would be bigger,'' said second-year guard Sam Vincent of his initial impressions, ``but everything about the Celtics seems to be on a more conservative scale.''

Everything, of course, except the team's record of excellence, which is built with plenty of shirt-to-shirt training camp basketball.