What could be better for the mental muscles than wrestling with a problem that has perplexed you for a dozen years and that leads you to different answers -- to a different balance of opinion -- every time you approach it?

For example, Fred Lynn.

Near the Baltimore Orioles' training site in Miami is a restaurant one in a baseball motif. Three walls are covered -- floor to ceiling -- by huge action photos. The owner could've chosen anybody who ever lived. He picked Babe Ruth, Roberto Clemente and Lynn.

That's how lots of people -- those who have voted him to nine American League all-star teams -- feel about Lynn, one of the game's vivid, graceful stylists.

Often it seems there are two Lynns. One was rookie of the year and MVP in 1975 -- an unmatched feat -- then won a batting title in '79 with a .333 average, 39 homers and 122 RBI.

That fellow has, for the last month, been carrying much of the load in keeping the Orioles alive in a pennant race. In 24 July games, he has 22 RBI and eight home runs. On Sunday, Lynn got his 10th game-winning RBI -- tied for the league lead. With a .307 average, 17 homers and 52 RBI, Lynn is having his best year since '79. When Lynn hasn't won games at bat, he has saved them in center -- running into fences and sliding all over the Memorial Stadium grass to snare toe-high liners.

Now for the bad news: the other Lynn. On Sunday, he gambled for an extra base, jammed his shoulder sliding and left the game. "We don't know how he is yet," said Manager Earl Weaver. "I hate to even ask . . . You're gonna blow out if you play ball like Lynn does. Some guys like Eddie Murray are not over-hustlers. They save a step here and there. They seldom get hurt and only get embarrassed a couple of times a season. Lynn's not that type, and you can't change him."

"Freddie has always played for the moment," said the Orioles' Mike Flanagan. "A lot of people enjoy watching that."

But it's a mixed blessing. Sunday evening, an Orioles coach looked at Lynn, holding his shoulder, and said, "When do you think we might get Freddie Lynn back in our lineup?" The answer: Lynn played last night against Texas.

He has missed 325 games in 12 years, sat out most of 50 others and averaged 468 at-bats a season. Because of injuries, most of them minor-but-nagging, he has spent 20 percent of his career benched. Because of all those pulls and sprains, Lynn has hit more than 23 homers just once, driven in more than 86 runs twice and really had only two genuinely eminent years.

Yet, when he plays, he's silk. Per 600 at-bats, he averages 100 runs, 36 doubles, 26 homers and 100 RBI, hitting .293.

But he has never had 600 at-bats. In fact, he has only made it to 500 once in the last seven years. Naturally, when Lynn sits, everybody talks. And the questions are always the same.

Why does he insist on running into walls and taking extra bases, even when his managers and teammates always make it clear that they wish he wouldn't?

Why does he prefer not to play when he's only at 80 or 90 percent efficiency, insisting that another man at 100 percent can do just as well? Doesn't he know that a great player's presence means more than mere stats?

Why, for years, has he taken days off against tough left-handers, with pennants on the line?

Why isn't Lynn, who knows how easily he gets hurt and how slowly he heals, more careful?

If you want to start an argument, bring up Lynn. Four weeks ago, after Lynn had missed 17 games with a sprained ankle and flu, I wrote: "Lynn only plays when he feels perfect. Firemen go into burning buildings for $25,000 a year, but Lynn won't go into center field for $8,333.33 a day if his ankle hurts. Asked recently to pinch hit with the bases loaded, Lynn said he didn't feel up to it. A potentially serious injury is one thing. But sore ankles and sore throats are the things pros play through; that distinguishes them from amateurs who play for fun, not for a living."

Weaver called my column "the most irresponsible" ever written about his team. One of his coaches told me, "Thanks, he Lynn needed that." And, in fact, the next week Lynn was the American League's player of the week.

Obviously, it's hard to find a calm middle ground on Lynn. Perhaps Carlton Fisk, his teammate for six years in Boston, does it as well as any.

"How bad did you nail Freddie, anyway?" Fisk needled me on Sunday.

"Maybe a six on a scale of 10."

"That's about right," said Fisk.

Okay, so maybe I got the "six" upside down.

"Remember," continued Fisk, "Freddie was a huge success with enormous expectations right away. He had to be perfect to live up to what he was supposed to do in Boston. So maybe he never wanted to go out there when he couldn't be that great all-around player.

"Also, most of his game is in his legs. If he can't run, he can't play the game the way he wants to. And most of his injuries are to his legs, or his back, which hurts when he runs.

"I remember what Gene Mauch said when Lynn had his best year in California," recalled Fisk. "People said Lynn looked like he was enjoying the game again. Mauch said, 'I think it's a case of Freddie reveling in his own good health.' "

Lynn has always played for the moment and for himself. He would no more pass up a chance to leap above the wall to steal a home run than a child could resist such a thought in his dreams. In pursuit of those moments of pure athletic fullfillment, Lynn, who went to Southern Cal on a football scholarship, is utterly fearless.

Sometimes Lynn does not return from his adventures in one piece. Then he feels the high demands of his public and the pressure of his critics. He loathes the thought of a hobbled, unworthy, embarrassing performance, even if it might help the team, even if he is being paid millions to provide it.

Early in his career, Fisk faced the same dilemma. He loved to block the plate like a hero. The result: His body was becoming a wreck. A decade ago, he gave up blocking the plate, even if it meant the game. Someday Fisk may set the record for most games as a catcher. Pride was the price of durability.

"But some people can't turn it off and on," said Fisk.

Fred Lynn always has wanted to have it both ways -- seize the moment and also perform only at his best. It's the sort of choice we'd expect more from an artist than from a pro athlete. He has done it his way and, as usual when you make that stubborn decision, paid a big price.