SOMEWHERE OUTSIDE BALTIMORE, JUST BEFORE 7 A.M. -- Four kids, whose ages range from 1 to 7, are snoozing in Matt and Adrianna Birk's cramped bed. They don't know that their daddy could've been a stockbroker on Wall Street, that a path of lesser resistance and stronger knees was waiting for him in his final months at Harvard. They don't know that crawling out of this bed will be one of the toughest things Birk does today.

No sick days. That's what Birk vowed when he made it to the NFL, that regardless of how he felt, he'd still wrestle on the floor with his boys and chase his little girls around the soccer field.

And on this morning, there will be plenty of running. Madison needs a ride to school, and Birk, a sturdy center who's in the final days of what the Baltimore Ravens hope is another playoff push, needs to mend a 33-year-old body that spent part of Sunday pounding against a 345-pound nose tackle in a cold, driving rain. He'll get little sympathy from his wife. She's eight months pregnant.

Birk pops one elbow, then the other, and fans his legs until his pelvic bone makes a cracking noise. He takes a couple of deep breaths, and his feet hit the floor. The first few steps are similar to tiptoeing through hot coals. But it'll get better; it always gets better once he makes it to the bottom of the staircase.

It's Monday, and time to start another week in the NFL.

Don't talk about it

There is no way to write this without some collective eye rolls from the lower tax brackets of the world. Sure, fellas, tell us about your aches and pains and your multimillion-dollar bank accounts.

Most players won't even talk about it, the price they pay, because in a league full of tough guys and a country with a 10 percent unemployment rate, it just comes across as whining. The game flashes over the TV for three hours on Sunday afternoons, and the average fan heads to work Monday without much thought as to what happens next. But when the camera lights dim, the next 48 hours reveal the true toll on an NFL player's body and how everyday life can be difficult to navigate.

Throughout three separate conversations in which Birk reconstructed for ESPN.com what a typical Monday and Tuesday feel like for a veteran, he wanted to make a few things clear: That he willingly signed up for this 12 years ago and has no complaints or regrets. That he feels lucky to play the game he loves, make a great living and be surrounded by teammates who ultimately become close friends.

Their bond, in large part, is forged from the fact that they're the only ones who know what they go through.

Ravens center Matt Birk is aware of the pain that probably lies ahead after years in the NFL. Larry French/Getty Images

It's a fraternity of long-term pain and lifelong consequences that are suppressed in a 17-week, suck-it-up-and-play vacuum. Pittsburgh Steelers receiver Hines Ward reflected that culture earlier this month when he initially questioned Ben Roethlisberger sitting in the thick of the playoff hunt while the quarterback was still suffering lingering effects of another concussion.

Birk, who once donated $50,000 from one of his game checks to assist retired NFL veterans, is keenly aware of what might lie ahead for his body 10 years from now. He just can't think about it. In December, all a veteran thinks about is survival. Can his body hold out for a few more weeks? Can he play the way he did in September?

"Guys play the game for different reasons," Birk says. "One of them is the challenge, the physical challenge, the mental challenge, to see how much you can take. How much you can withstand. And it's about developing that perseverance every week. Getting your body and your mind ready to go.

"I mean, everybody's sore. Everyone who played yesterday is sore today. That's just part of the game, and you're not going to last if you can't deal with it."

Birk settles in with a cup of coffee on the Monday after the Lions game earlier this month, Victory Monday, which means the Ravens get the day off. But it's never really a day to relax. His ankles, knees and fingers are sore. His shoulder hurts. That popped this morning, too.

When he got into his truck, he had to lower his head, which triggered a fairly constant pain in his neck. Birk has spent various parts of the season on the injury report because of his neck but hasn't missed a game in three seasons. On Sundays, he says, the adrenaline is flowing and the pain disappears. Mondays are the proverbial hangover, a time to assess the damage. On this particular day, Birk says all is good. He escaped the game with just a few cuts on his hand and a gash above his nose from his helmet. That might affect his modeling career, he jokes. Nothing will change his status for the next game.

Some weeks are worse than others. When Birk goes up against Casey Hampton, the Steelers' massive nose tackle, he always seems to feel a little worse on Monday. One thing is certain: The second half of the season seems to grind at a much slower and harsher pace. If you're lucky, you have a perfectly placed bye week at midseason.

If you're smart, you don't spend Monday in bed. Birk always has been proactive when it comes to his body. The day after a game, he heads into the Ravens' facility to lift weights and "flush out" the toxins and soreness. He stretches. The Ravens have team chiropractors, and Birk takes advantage of the perk and usually sees them on Mondays.

"There's a joke that somebody, some jackass -- usually me -- always says when you're putting pads on that first day of training camp," Birk says. "They say, 'Remember how good you feel right now? It's as good as you're going to feel for seven months.'"

It's only a slight limp

The thing is, the Day After doesn't affect just the graying veterans. It hits just about every first-string player. Barrett Ruud is only 26 years old, and he's been a starting linebacker for the Tampa Bay Buccaneers for a little more than three seasons.

Matt Birk says soreness is just part of the game, and "you're not going to last if you can't deal with it." Elizabeth Merrill/ESPN.com

But he feels significantly older from the cumulative toll of a 16-game football season. On Monday, hours after his team knocked off the New Orleans Saints, Ruud's entire body ached. His elbows have been sore for the past 10 weeks. They seem to feel better only on Sundays. The first series of the game against the Saints, Ruud took a shot to his knee. The next day, he walked around with a slight limp.

Ask him how he feels, and Ruud says, "I'd basically say I feel like Monday. I feel like it's a good Monday. I don't have any serious injuries, but I have a good soreness from a win. If you're not sore at all on Mondays, it usually means you didn't do a lot on Sunday."

Ruud, at least, had fair warning. His dad, Tom, played five seasons in the NFL. And when Barrett was 4 years old, Tom handed him a golf club, not a football. Tom Ruud is 56 and lumbers around with crushed vertebrae. The longer you play, he says, the more trauma you inflict on your body.

"There's always pain," Tom says. "That's just part of the deal."

Whenever he sits down to watch a football game, he doesn't worry about just his son; he worries about every player on the field. But he knows Barrett is uber-body-conscious, with everything from massages to his strict diet. The kid ate a greasy hamburger the other day. It made him feel sluggish for two days.

Ruud knows what his body likes -- Mondays in the cold tub; Tuesday rubdowns. His body has delivered 446 tackles during the course of five NFL seasons. Artificial surfaces, Ruud says, always seem to make him more sore.

He's still rookie-fast on the field, but Ruud has noticed that it takes him longer now to feel better. That's why, like most players, Ruud is very interested in the talk of the NFL possibly expanding to a 17- or 18-game season. He wonders what that would mean for the recovery process.

At the end of every season, Ruud takes about four weeks off, does basically nothing, then slowly weans himself back into a workout routine. By the spring, he has recuperated enough to walk 18 holes and hang out at the pool in his hometown of Lincoln, Neb. By two-a-days, he's refreshed and ready to take more punishment.

"I grew up around a lot of college and NFL players," Ruud says. "I saw some of [my dad's] best friends who had 15 or 16 surgeries. The more I played and the higher up I got, I started asking questions.

"I don't think there's any doubt those guys had a lot more fun than we do now. We can't go out and drink beers every night of the week and still feel good. We've got to be a little smarter."

Cold weather contributes

When Birk pops various parts of his body every morning, he jokingly calls it "his body's way of resetting itself." He compares playing in cold weather to starting an old car. It takes a while for the older guys to get their joints warmed up and moving.

Dr. Neal ElAttrache, director of sports medicine at the Kerlan-Jobe Orthopaedic Clinic in Los Angeles, has more technical definitions of what is probably going on in Birk's body. As NFL players get older, they're more likely to have arthritis in the joints they rely on so heavily. Cold weather triggers arthritic pain.

ElAttrache is the team doctor for the Los Angeles Dodgers and worked with the Rams when the franchise was in Los Angeles. He saw many a macho football player shrug off the pain as something a man deals with when he plays in the NFL. ElAttrache has worked with many athletes from various sports, but he says professional football players are known to have some of the highest tolerances to pain.

It's not like the movies, where a trainer shoots a player up with pain meds on Mondays to help get him through the week, ElAttrache says. "That's not a time to numb these guys out," he says. "On Mondays and Tuesdays, they're going to be on anti-inflammatories. What you're typically doing is electrical stimulation, ice, massage. Those kind of things help get the flexibility back so they're not so stiff."

Tuesdays are generally the worst days in terms of soreness, he says, because that's when the joints become stiff and inflamed. Tuesday is the official day off for players during the regular season.

"What's very common is that their respect and their limitations to their pain are far different off the field than on the field," ElAttrache says. "When you're getting ready for a big game, or even in practice, that adrenaline goes through you and tends to override the pain.

"Take that away, that sort of fight-or-flight mechanism, and you're left with raw discomfort and a markedly less functional guy. A guy walking on tiptoes or not at all."

Will he be able to play with the kids?

There are times during the offseason when Birk's body is "healed" that someone will ask why he's limping. He doesn't really have an answer; he figures maybe it's just a 33-year-old football player's normal gait.

Tampa Bay linebacker Barrett Ruud goes to the cold tub on Mondays, and gets rubdowns on Tuesdays. AP Photo/Brian Blanco

In the fall, one of the most painful things he does has nothing to do with blocking. It's when he's on the floor, playing with his kids, and tries to pick himself up. Birk wriggles and struggles and pushes with his arms and shoulders. That's when he feels the rigors of the NFL the most.

Sure, he thinks about it, when he's away from the grind of the season and rolling around like a bear during playtime with his kids. Will he be able toss a football to his sons when he's 45? Or simply bend over to pick it up off the grass? History tells him it could be a struggle. Birk, who's active in Gridiron Greats, a group that assists NFL retirees, runs into friends who limp and move about at an old man's pace. Some of those guys played alongside him in the late 1990s.

He vows that he won't let his sons play tackle football until they're older. It's too violent for a 10-year-old, he says. And he doesn't think that pain, so young, is necessary.

Yet Birk is a recipient of it every week, and he still wants to keep playing until his body tells him he can't. It might not make sense. But it's clear to the players.

"You get so much from the game," Birk says. "The camaraderie, the friends you make. You don't mind having to pay that price because you get so much out of it.

"I've been pretty lucky, and medicine's always progressing. Things are always getting better. Am I going to feel like maybe running marathons? Probably not. That's OK. I don't worry about it. I'm not going to let this stuff slow me down. It's kind of like mind over matter. If you don't mind, it doesn't matter."

Elizabeth Merrill is a senior writer for ESPN.com. She can be reached at merrill2323@hotmail.com.