It has been said that life begins at 40. Though often, it seems these days, with some help from Viagra.

Life in professional sports usually ends at 40, or long before, even for the great ones.

"I remember many years ago talking about how age 33 was the pivotal age for guards," said Lakers coach Phil Jackson, who retired as a player at age 34. "Oscar (Robertson) was about 33 when he got a championship and the next year the wheels fell off. Walt Frazier the same thing (both played until they were 35). Jerry West played until he was 35. I don't remember anyone before Kareem (Abdul-Jabbar) playing after 40. I thought big guys would have a chance. But now you see guards who do, and it's the most athletic position for body stances, having flexibility and durability, picking yourself up after a pick and going on with the play. It's remarkable."

Utah Jazz point guard John Stockton turned 40 late last season and continues to play. This February, another guard will be added to that list as Michael Jordan joins a select group of fewer than a dozen players in NBA history to play after their 40th birthdays -- health permitting for Jordan this season, of course. And, undoubtedly, Karl Malone will join the list next season, since those close to Malone expect him to play for several more seasons in his quest to break Abdul-Jabbar's all-time scoring record.

	Michael Jordan, right, will rely on brains more than brawn.

What once was considered unthinkable has become the accepted in this era of improved training techniques, luxurious travel, bigger paychecks and the love of the game. Or not.

"I played (until a month before turning 40) for the opportunity to make some money that I didn't make early in my career," said Eddie Johnson, now a Phoenix Suns broadcaster who played for six teams in a 17-year career that ended in 1999. "I don't know about young guys now, whether they'll do that. They make in five or 10 years what it would take me to make in 25. Karl Malone didn't make money until the end of his career, the same with Scottie Pippen. I think that's why they played a long time. I can't see that with guys like Tracy McGrady, Vince Carter and Stephon Marbury. But who knows."

Perhaps the test for the over-40 set will be this season when Jordan turns 40. He is regarded by many as the game's greatest player, but his body started to desert him last season and he required knee surgery. Many question whether he'll hold up to make it to 40 in February, and the Wizards have talked both about limiting his playing time and even bringing him off the bench.

"I may not have the wind I've had over the years but I'm older, too," Jordan acknowledged. "But I'm also smart enough to know how to play the game, and as time comes physically I'll be ready."

But it remains a question because results have not been positive for those who've made it beyond 40, not counting Dikembe Mutombo, who is listed at 36 but said by some to be at least five years older.

It's clear that bodies break down from so much stress, and it apparently has come now for Hakeem Olajuwon, who turns 40 in January. He signed a contract with Toronto to play several more seasons but failed his physical and was let go by the Raptors this season. Olajuwon had been one player who always said, unlike Jordan during his two retirements, that he truly loved the game and would play as long as he could. Apparently, he has reached that point. Likewise with Patrick Ewing, who turned 40 this past summer. Ewing wanted to play another season and even hinted at being ready if called upon when taking a job this season as a coach with the Washington Wizards. But his body, also, failed him.

"I remember talking about how I'd like to play 10 years," recalled Rick Mahorn, a broadcaster with the Detroit Pistons who played until he was 40 and retired in 1999. "Then I ran into Caldwell Jones who was doing his year-to-year thing. He said, 'Whatever you do, only retire when they don't want to pay you anymore.' I took his philosophy. The key, obviously, was not being hurt. Though expansion helped a lot."

The addition of four teams in the late 1980s and then two more in the mid-1990s created many more jobs and enabled mostly veteran big men to hang on. Such was the case with the likes of James Edwards, Mahorn, Herb Williams and Moses Malone. Also, several centers played to the verge of their 40th birthdays, including Artis Gilmore, Jones, Alton Lister, Danny Schayes, Tree Rollins and Sam Perkins.

In addition to Edwards, Mahorn, Williams and Malone, those who played past their 40th birthdays include Robert Parish, the league's oldest continous player ever at 43, Abdul-Jabbar, Stockton, John Long (in a brief comeback with Toronto at 46), Kevin Willis (now with the Spurs) and Bob Cousy (briefly at 41 with Cincinnati six years after retiring from the Boston Celtics).

"It was a promotional thing with Cincinnati," said Cousy, who was a first-year coach then with the Royals. "I quit at 35 and could have played with the Celtics until I was 41. (Bill) Sharman and I were backed up by K.C. Jones and Sam Jones, Hall of Famers. But I began to realize I no longer had the skills to be the go-to guy."

"Michael has surprised me," added Cousy, still an occasional Celtics broadcaster. "He's impacted the team, not to the degree he did before. But he's been more effective than I thought he would be. A lot depends on the shape you keep yourself in and your supporting cast. Parish had those bookends in (Larry) Bird and (Kevin) McHale. It neutralized the pressure on him to do it all.

"For me, leaving on top with a championship and then exploiting what I'd done to build a foundation for the future made sense. It made more sense than dragging it out and playing a lesser role.

	“	"Michael (Jordan) has surprised me. He's impacted the team, not to the degree he did before. But he's been more effective than I thought he would be. ”
		— Bob Cousy

"Today you can hang on. The last five or six teams in the league, I'd say wouldn't beat most good college teams. You can also stay around if you're a future Hall of Famer with a high profile. But you know, if you are honest. You've got to sit yourself down and admit it's time. Most athletes want to quit on top with the brass ring, and that entered into my thinking. I suppose I could have had 11 rings like (Bill) Russell instead of six. But it was time."

That's often hard to say, especially these days with inflated salaries and the first-class lifestyle NBA players lead.

"You've got to look at the private jets, the hotels on the road," Mahorn said. "When I started we were on commercial flights, and that makes a difference. Plus you have the athletic training centers and you're able to build your body and keep in shape like we never did."

Though some, like Johnson, believe the trend toward 40-plus players will remain a rarity because the younger players don't understand what the guys who played at 40 did.

"Look at Karl Malone," Johnson said. "You have to marvel at how many times he's hit the floor and bounced up. They don't make players like that anymore. Players today don't take being in shape that importantly. They rely so much on athleticism. They don't stretch and ice, and their bodies tear down.

"An example," said Johnson, "is a guy like Allen Iverson. I said when he came in that he was a 10-year player and I still say that. You cannot survive not taking care of your body. Guys wait too late to do it. Kevin Johnson is a good example. I'd stretch and he'd always be laughing at me. I said he had to stretch. Then he got a hamstring (injury) which turned into a back problem and he never was the same. I see that happening to a lot of young guys."

Frankly, few of the old guys have performed that well after 40. Abdul-Jabbar was probably the most productive, averaging 14.6 points per game and then 10.1 in his final season -- though both were career lows -- his final season being about a third of what he scored as a rookie. Parish averaged 11.7 points when he hit 40 in Boston, but then never more than five points per game sticking around with Charlotte and the Bulls for three seasons.

Mahorn, Edwards, Williams and Malone were just hanging on after they hit 40, but Stockton was a marvel, averaging 13.4 points and ranking among the league leaders with 8.2 assists last season. And Willis turned 40 in September and insists he can help the contending Spurs.

"This is just something I love doing," Willis said. "It's pretty much all I've done my adult life. I could play two or three more years for sure. It's just a matter of whether the energy and the mental part of the game is still there. If it is, I will."

However, he may get a tap on the shoulder sooner than he'd hoped from the inevitability of time.

"You never beat time," said Mahorn. "But I had a good time trying."

Sam Smith, who covers the NBA for the Chicago Tribune, is a regular contributor to ESPN.com.