To each his oar

ROWERS are as common on the Charles River as pigeons on Commonwealth Avenue's beautiful brownstones. For more than a century, they have been a consistent sight on the river from dawn to dusk - yet they remain a largely unnoticed group.

Here in New England, rowing and college go hand-in-hand. The Charles is dotted with university-owned boathouses. Students train fall and winter for the official opening of the crew season in spring. At practice, rowers dip the oars in and hoist them out of the river hundreds of times daily, striving for unison and uniformity.

''You must almost be crazy to row,'' says one oarsman from the Massachusetts Institute of Technology (MIT). ''People find it hard to believe that oarsmen train so hard, so many months in advance, to row well for a six-minute race. Many races are backed by 300 to 400 hours of practice.''

Why do these students devote themselves to their sport? There is no fame or fortune in rowing - no one has ever seen an oarsman's picture on a box of Wheaties.

''The reward of victory is worth it,'' explains the MIT oarsman.

''It's definitely not a glory sport'' says Lisa Stone, women's crew coach at Radcliffe. ''And it's a combination team and individual sport. Think about it - there are eight rowers in a shell, yet each is completely alone because none can make eye contact with another.''

Though rowing is predominantly a college sport, it got its start from seasoned river boatmen.

Competitive rowing began more than 400 years ago in London, when boatmen on the crowded Thames River began to hold races among themselves. It was not until 1829, however, that rowing was introduced to the world of sport when students at Oxford and Cambridge Universities raced 7,000 yards on the Thames. The race - still 7,000 yards - has been a fierce rivalry ever since.

Ten years later, the British served as hosts for the first international rowing competition - the Royal Henley Regatta, now an annual event.

The sport of rowing crossed the Atlantic early in the 19th century. Clubs sprang up in New York, Philadelphia, and Boston, but not until the universities took up the oars did crew gain acceptance in the United States.

In 1843, Connecticut's Yale University became the first American school to adopt a form of rowing. The original ''shell'' was a dugout canoe. The next year , another group of Yale students bought a lapstrake gig and challenged the men with the canoe. The canoe defeated the gig by a half-mile. When members of the gig crew hoisted their boat from the water, they discovered they'd been towing an anchor. Someone had tied a rope - trailing a huge slab of stone - to the gig's keel.

The first intercollegiate race was in 1852 between Harvard and Yale, and it started the most longstanding rivalry in New England. Whoever wins this year's race (June 3) will qualify for the National Collegiate Rowing Championships in Cincinnati.

College rowing in the Northeast is divided into several divisions. Biggest of these are the ''eights'' - boats (called shells) manned by eight men or women, plus a coxswain. Students row in fours, they row in twos, and they do it alone (sculling), but eights grab the limelight. And rightfully so.

To coordinate eight oars into a powerful, smooth-moving force is no easy task. Some rowers believe the precision needed in eight-person rowing makes it the ultimate team sport. Each rower is working only one of the participating oars, yet all the oars must function as a perfect multipede - or the team faces certain defeat.

Many New England colleges begin training when school starts in the fall, even though the official rowing season doesn't open until spring. Surprisingly, a large number of rowers have never rowed before college.

''Here at Boston University, around 90 percent have never rowed before,'' notes BU Coach Bill Miller. ''The ones that have usually went to a prep school.'' BU, like other schools, has a freshman team and a varsity team. And from the start, coaches monitor the training and improvement of everyone who goes out for the team. On average, more than 100 students join in the fall, and 50 or 60 are still hanging in there come spring.

Some drop out because of the rigorous training and commitment. Sacrifice, most rowers agree, is the name of the game.

''The whole year is a series of sacrifices for the well-being and morale of the crew,'' explains one seasoned competitor from Harvard. And the training is not entirely physical. ''Crew is a thinking man's sport,'' says oarsman Alfred Escher of Princeton. ''To be good, one has to really think about every stroke.''

To the novice, simply boarding the shell can become a wet, embarrassing adventure. The shell of an eight-person crew is about 60 feet long, two feet across, and less than 1/4-inch thick. A misplaced foot in the shell will take you and the boat to the muddy bottom in seconds. From then on, the going gets rougher.

Rowers strap their feet into shoes that are stationary in the shell. Their seats slide backward and forward, allowing rowers to use the power of their legs and backs to accelerate the shell. And each oarsman must be in perfect coordination with the others. ''That's what we watch for in the winter,'' says BU Coach Miller. ''We monitor every breath, heartbeat, and stroke our guys take.''

Winter training is usually the most intense. It involves rowing machines, running, weight-lifting - and the infamous row tanks. Alongside the tanks run rushing pools of water. The coach can, with the twist of a handle, increase the water being pumped through the tank, simulating downstream or upstream rowing.

But one cannot speak of training without mentioning Harvard and Radcliffe's claim to fame: Harvard Stadium.

The horseshoe-shaped stadium is a sort of proving ground for Harvard rowers. This is where they run - but not on the field. Instead, the athletes daily run up the stone benches and down the aisles in all 37 sections of the grandstand. At full speed.

And don't think the women of Radcliffe or other schools have it easier then the men.

Radcliffe's Coach Stone says the women run up and down the stadium, work in the tanks, and lift the pounds just as hard as the men. The women, she points out, train five days a week in the fall, five days a week in the winter, and at least five days a week during the spring season. The work is paying off for this year's Radcliffe crew, which is off to a winning season. The team is gearing up for the National Collegiate Championships in Seattle next month.

Most women, like the men, discover crew in college. ''Initially it just catches their attention,'' notes Coach Stone. ''Some girls who were good high school athletes give it a shot.''

One member of the crew - the coxswain - does not train as hard as the others. In fact, the smaller and lighter the coxswain, the better. They are the ones who monitor bladework, balance, timing, and power in hopes of making the shell a winner. (They also must have the common sense to avoid the many bridges on the Charles.) The coxswain decides when to sprint, determines who is missing a stroke, and keeps up the tempo. Perched at the rear of the boat, a coxswain can see if the shell is ahead or behind, and plots strategy accordingly.

Though the fall is the training season, one race attracts shells from every corner of the US. The annual Head of the Charles Regatta, sponsored by the Cambridge Boat Club, began in 1965 with 100 boats in the race. An instant success, it now attracts more than 1,000. The race - open to eights, fours, twos , and singles - covers three miles beginning in Boston and heading west.

Still, for all the crews' training, the public usually ignores the shells on the Charles. Unlike baseball or football games - which are picked up by radio, television, magazines, and the front pages of newspapers - crew remains an unglamorous sport. There are no rowing stadiums, and tickets are not sold to rowing events (except in the Olympics). There are and never will be individual superstars in rowing.

After all, at the finish line the boat is recorded as the winner - not the rowers.