"IF IT WEREN'T for this, I would be sitting home in my rocking chair," reads the notation on the stationery of the Northern Virginia Seniors Softball League.

Don't believe a word of it. The real rocking by this group of 50-and-over players comes on the base paths in celebration of their latest hits.

The Northern Virginia league is the best organized and most competitive of several in the Washington area offering seniors softball as an alternative to card games, bingo and golf. With more than 200 members, it will play league games at Wakefield Park two days a week starting in May, conduct an instructional program for novices every Wednesday and send various teams throughout Virginia on weekends trying to promote senior softball.

Other organizations in Rockville, Sandy Spring, Emory Grove, Silver Spring, Wheaton and Greenbelt have teams that play weekdays, weekends and in some tournaments, which is a growing trend in senior softball. Last year, the Northern Virginia league sent teams to tournaments in Las Vegas and Detroit.

No one should make the mistake of thinking seniors softball is played at the equivalent pace of a walk to the Metro station. Most games are played with intensity. Slight rules variations from regular slow-pitch softball -- 11 players instead of the regular 10, no sliding, any base can be overrun without penalty and a prohibition against runners purposely colliding with fielders -- help keep injuries to a minimum and extend careers.

Several players in Northern Virginia and Montgomery County, for example, are 80 or older. Bob Swortzell, organizer of the Northern Virginia league and a walking press guide on the backgrounds of practically every one of his league's players, said his organization has eight members who have had heart bypass surgery. Harry Logiodice, 80, has two artificial knees, but remains a regular pinch-hitter with the aid of a substitute runner.

All teams are co-ed and welcome players throughout the season. Some regulars have kept their hand in for decades, but other players, who often turn to softball as an entree to other social activities, have rediscovered the game after years away from it.

"I had not played any ball since American Legion[teen-age] baseball," said Russ Reber, 64, who retired from his data processing job nine years ago. "My first three years of retirement I sat around doing crossword puzzles until I saw an ad for the Northern Virginia softball league. Until then, the only physical thing I had done for many years was to mow my lawn. Now, whenever I see someone, all I want to talk is softball."

This summer, Reber will maintain a schedule many softball players 45 years his junior would envy. He will spend weekends traveling with Northern Virginia teams for their barnstorming games, play in the regular league on Tuesdays and Thursdays, help with the novice league on Wednesday, and manage and play with a team of seniors that has played in an open (no age limit) Fairfax County recreation league.

"Most of the other teams don't take us seriously, at first," said Reber. "But we usually can stay with most of the teams, and we have won three or four games [out of 14] each of the four years we have been playing. They take us seriously the second time we play them, even though quite a few of the other players could be our grandsons."

The Greenbelt organization takes its softball somewhat less seriously.

"It is exercise, and it is social -- at least that's what we say when we lose," said chairman Burt Kerr, 59, who played softball for the first time in his life four years ago. "But we find a place for everybody. We have one lady who can't bend over or run, so we let her do something like pitch or catch so she doesn't have to move around too much."

The softball skills that diminish most through the years are throwing and speed, the seniors find.

"Whatever speed a team has must be used in the outfield because eventually, it will save a lot of problems," said Dick West, 60, one of the Northern Virginia league's top players. "But to play well when you get a little older, all you have to do is be a little more clever."

Swortzell enjoys promoting the softball league as much as he does playing. He said many of his organization's members discovered new off-the-field energy through the league. Functions such as dances have become regular features.

"When the games are over and it is time to go home, a lot of people don't want to go home," said Swortzell. "They end up going out afterward to drink sodas and chew the fat. We end up with people playing tennis and golf together, but if it weren't for softball, a lot of them might have just ended up raking leaves by themselves."

Reber said many people, reluctant to come out initially, surprise themselves on the field.

"Some people keep their skills better than others, but, like I found, you can compete against your contemporaries. I continued to do some work on the side when I retired, but now, I tell people I can only work for them if it doesn't interfere with my playing -- that comes first." IN THE SWING

Games on the seniors circuit begin May 3 and 4 and run through mid-August. The Northern Virginia League also has a fall season that runs from September to mid-October. Many teams are already practicing, but all the programs say they accept players even after the season has started. The main season runs through mid-August.

NORTHERN VIRGINIA -- Seniors softball games at Wakefield Park, 8100 West Braddock Road, Annandale. Contributions of $25 requested. Call 281-1819.

GREENBELT -- Games at Braden Field, 15 Crescent Street, Greenbelt. No fees. Call 474-9498.

ROCKVILLE -- Games at Woodley Gardens, on Nelson Street in Rockville, across from Woodley Gardens Shopping Mall. No fees. Call 424-8000, ext. 353.

MONTGOMERY COUNTY -- Games at various sites in Sandy Spring, Emory Grove, Silver Spring, Wheaton. Fee $1 per person per game. Call Montgomery County Recreation Department's senior adult program at 468-4480.