One hallway at the Eagles' NovaCare Complex has framed pictures of every Pro Bowl player in franchise history.
The photos hang in chronological order, so a person can trace some of the many changes that have come to the NFL - in race, equipment, and fashion.
Two transformations have continued consistently: The players have gotten bigger, and the leg protection they wear has gotten smaller. So small, in fact, that the majority of players in the league don't wear any padding below the waist.
Even though they were required to don thigh, knee, and hip pads from peewee football through college, many players, once they reach the professional ranks, ignore such recommended equipment because the NFL doesn't require it.
"You start out real young, and you want the biggest thigh pads you can get to make the most noise," Eagles wide receiver Jeremy Maclin said. "But as you get older, you kind of want less and less equipment on you, and finally you get to the stage where you don't have to wear any pads. It's just kind of a thing that everyone does, and you just kind of do it."
With the Eagles' Brian Westbrook having suffered two recent concussions, the safety of NFL players has become an increasingly debated topic.
NFL commissioner Roger Goodell said during recent congressional hearings and elsewhere that the NFL is trying to make the game safer, and few would argue that the handling of concussions is much better now than it used to be.
But while head injuries are more significant than leg injuries for long-term health, there is incongruity in the way the league allows its players' legs to go unprotected.
The NFL rule book has 153 words devoted to requirements related to socks and how much of which colors can be shown. At every NFL game, a league official checks whether players are wearing socks and the rest of the uniform properly. A first offense can mean a $5,000 fine.
The rule-makers needed only 74 words to say the league "recommended that all players wear hip pads, thigh pads, and knee pads, which reasonably avoid the risk of injury. Unless otherwise provided by individual team policy, it is the players' responsibility and decision whether to follow this recommendation and use such pads."
Asked why wearing pads is not mandatory, an NFL spokesman responded in an e-mail by essentially rephrasing the rule.
Fans would notice players without helmets or shoulder pads. They might not notice players without leg pads.
The NFL likes fast action, and not using leg pads allows players to run faster. If the NFL required all players to wear such pads, all players would be a bit slower. A speed reduction might also help with concussions.
But by only recommending the use of leg pads, the NFL puts the player in position to choose between greater safety and greater speed. And with most contracts not guaranteed and job security tenuous, players are desperate to find any advantage they can to succeed.
Even if the league changed the rule and enforced it, there would be some rebellion, and players would find ways, literally, to cut corners.
"Guys wouldn't be happy," Eagles linebacker Chris Gocong said. "I'm sure they'd just find another way to shave their pads down or something like that. Guys are going to find a way to be comfortable on the field."
When the NFL made it optional instead of mandatory in 1995, it was mostly the speed-position players - receivers and cornerbacks - who went without the lower- extremity pads. But the game has gradually become all about quickness, and players at every position are looking for any edge.
"As an offensive lineman you take so many shots with your hands and shoulders, you don't have to wear them," Eagles guard Todd Herremans said. "We worry about speed, too. We're not big, slow animals. We can move, especially if we get out on the edge."
At the lower levels of football, participants are required to wear the protection for insurance reasons. But as players get older, they find inventive ways to whittle down their gear. In college, they're supposed to wear butt pads but not many do.
Maclin, a rookie, briefly entertained the idea of wearing thigh pads after suffering a deep bruise during a preseason game. Like practically every other receiver in the NFL, he decided otherwise.
"It's about being as light as you can be," Maclin said. "Honestly, how big of a difference are thigh pads going to make? . . . Receivers don't get hit much in the legs."
So who does get hit in the legs? Mostly the running backs.
Westbrook, who has also missed time because of off-season knee surgery, often does not wear knee pads.
Eagles fullback Leonard Weaver is one of the few players on the team, if not the only, to wear knee pads along with thigh pads. He said he doesn't care if he doesn't look as sleek as some of the other players.
"Knee pads are significant for me because guys have a tendency to aim at your thigh but hit your knees," he said. "I'm a bigger back, and I'm more prone to be cut lower, hit lower, because guys aren't generally going to take you high."
Gocong, like many of the team's linebackers, wears just thigh pads. Still, he takes blows on exposed areas that would otherwise be protected by padding.
"You'll randomly catch a knee in the quad or whatever," Gocong said. "That's football. I get my hands stepped on, but I'm not going to put a pad on my hands."
In the late 1980s, the NFL banned blocking below the waist on changes of possession. Chop blocking - a block below the thigh - is illegal. Because of the restrictions on blocking, Eagles linebacker Jeremiah Trotter said that players shouldn't need leg padding, and that wearing it should remain optional.
"It's the NFL, and you should know how to protect yourself by now," said Trotter, who goes with just thigh pads. "If you don't know how to hit and tackle and protect yourself at this point in your career, then you don't need to be here."
Weaver, who has dealt with mild teasing from teammates for his choice of armor, said peer pressure could be involved.
"It's a fashion statement for most people," Weaver said. "Some people are just more comfortable with it. Everybody has their own reasons, but for me it's all about protection."