Chip Kelly said that there is a direct correlation between the few soft tissue injuries the Eagles have had this season and the team's sports science and conditioning programs.

The Eagles, comparatively speaking, have been among the healthiest teams in the NFL through the first four weeks. They have averaged only 3.5 players per week on the injury report, well below the league average of 8.8. Only the Chicago Bears have had fewer.

They Eagles have had only two starters miss games - cornerback Bradley Fletcher sat out against the Chargers with a concussion and safety Patrick Chung missed Sunday's game in Denver with a bruised shoulder.

The NFL issues a practice participation report for the league Wednesday through Friday. On Wednesday, there were 9.3 players per team on the list, 4.1 who didn't practice, 3.3 who were limited and 1.9 who were full participants.

The Eagles had no injured players who didn't practice or were full participants, and only Chung and cornerback Brandon Boykin, who also has a bruised shoulder, were limited. (Boykin was upgraded to full on Thursday.) Only the Atlanta Falcons and New York Jets were healthier.

"I think the one thing we are happy with in terms of how we approach things is that we don't have a lot of soft tissue injuries, don't have a lot of muscle pulls," Kelly said Thursday, "and a lot of that directly correlates back to what we are doing in the weight room and from a conditioning standpoint."

The program hasn't paid off yet in terms of wins and losses. Early in training camp, the Eagles lost four players for the season to torn anterior cruciate ligaments in their knees, including starting receiver Jeremy Maclin. But they have not suffered a significant injury since.

And minor injuries like hamstring and calf strains, as Kelly noted, have been virtually nonexistent. Teams are required to report all injuries or face league sanctions.

"There's a method to the madness, hopefully, and we'll see if that continues to help us," Kelly said, "because it is a long season."

Kelly, his staff and the players have been reluctant to talk about the programs, especially sports science coordinator Shaun Huls and his methods. The Eagles coach credited the players and how they have embraced the program and some of its abnormalities, such as an extra day of practice.

"We practice on Tuesday. Who else is practicing on Tuesday?" defensive end Clifton Geathers said. "But you can't tell a dog to hunt if he never hunted before. We grind every day believing in something that we never did before."

Geathers is with his sixth team since being drafted in 2010. His father, two brothers and an uncle have also played in the NFL. He said the Eagles do it differently than most teams.

"I never hit sleds every day. We hit sleds every single day," Geathers said. "We do pods, which is double teams, every single day. We pass rush every single day. I condition every single day."

Geathers said he took 1,400 exercise repetitions on Tuesday, but would not reveal the weight machine he used. The 6-foot-8, 340-pound end also said he lost 12 pounds from the time the Eagles' conditioning staff weighed him in the morning to after practice in the early afternoon.

Geathers said he had to get hooked up to an IV on some days to replenish fluids.

"It's doing something so much to where you're used to use to it," Geathers said. "Peeing every day and getting hydrated. I do a [urine] test every single day. But there isn't much more I can tell you - from the things that we wear to the sports science."

Kelly and his staff have educated the players on the obvious benefits of eating the right foods and getting enough sleep. But there's much more to the sports science angle. Players wear heart monitors during practice and have their body temperatures regularly monitored.

LeSean McCoy was spotted wearing white booties with odd-looking cushions in the locker room on Thursday but asked a reporter not to photograph them because he said Kelly wouldn't like it.

Kelly said that the Eagles spend a lot of time on recovery, and not just after games. He said one of the reasons they practice on Tuesdays - unlike every other team in the league - is that there has "to be a workload and a certain amount of practice" to recover from.

Quarterback Michael Vick, who has missed 11 games in the last three years because of injuries, said that he believes the program has helped him bounce back from the inordinate amount of hits he continues to take at his position.

"I haven't felt like this in a long time," Vick said. "Come game time I just feel fresh and feel like I've been in my best shape in a long time."

Lane Johnson's model

Long after most of the Eagles had left the visitors' locker room in Denver, Lane Johnson sat at the foot of Jason Peters' stall and listened.

The Birds had just been pasted by the Broncos and the rookie right tackle had another rough outing. Johnson has attached himself to Peters' hip. Although Peters hasn't been as dominant as he was in 2011, pre-Achilles tendon rupture, the five-time Pro Bowl left tackle has wisdom to impart.

"He really tells me about staying balanced," Johnson said this week. "Whenever you're lunging or leaning, that's when you're going to get beat. That's what he preaches most."

Peters, like Johnson, was late to the offensive line. In fact, Peters didn't start playing tackle until his second season in the NFL, after the Bills signed him as an undrafted tight end out of Arkansas.

Johnson played quarterback, tight end and defensive end before Oklahoma moved him to tackle in his junior season. He's had a head start over Peters. But Peters wasn't selected fourth overall in the draft like Johnson and wasn't under a megawatt spotlight.

"He struggled - well, everybody struggles when they first get in the league," Johnson said. "His deal is he likes to go attack guys. So I'm trying to watch him and emulate what he does."

Inside the game

Bennie Logan has played 32 percent of the snaps on the defensive line this season, but the Eagles have credited the rookie with only four tackles. Geathers, who has played 21 percent of the time, has eight tackles, by comparison.

Logan, who performed well in the preseason, had a theory behind the drop-off.

"In the preseason I'm constantly rotating. Now, I'm sitting on the sidelines for a quarter and a half or something like that," Logan said. "And by the time I do go in there I'm cold and stiff. . . . I've got to find something to do to keep me warm and keep my blood flowing on the sideline."

Eagles defensive coordinator Bill Davis used an umbrella zone against Denver, allowing short passes underneath. While Peyton Manning picked the scheme apart, linebacker Connor Barwin said that he didn't expect it to go away.

"Part of our philosophy is not to give up the huge play, to not let people get behind us in our zones," Barwin said. "I think that's going to be the same thing every week."

Kelly said that he wasn't concerned about the New York Giants signing offensive lineman Dallas Reynolds, who spent most of the preseason with the Eagles, the week before Sunday's game.

"We are not doing everything the same way we did it from the communications standpoint that we did here in preseason," he said.

Inside the locker room

Chris Polk had a productive first six offensive snaps in the NFL, rushing three times for 33 yards and a touchdown and catching two passes for 21 yards against the Broncos. He said watching similarly-styled running backs like Marshawn Lynch and Ray Rice has helped him to maximize picking up yards. "I see it as a fight," Polk said. "You're not going to go in with your hands down. You want to swing first." . . . Damaris Johnson played 235 snaps last year, was targeted 28 times, and caught 19 passes for 256 yards. This season, the wide receiver has played only 15 snaps and has not been targeted at all. Johnson said he thought he'd play more. "As of now, it's not working that way," he said, "but it doesn't change how mentally focused I am."

By the numbers

The Eagles have used the same offensive lineup - Michael Vick, DeSean Jackson, LeSean McCoy, Riley Cooper, Brent Celek] and the starting offensive line - for 53 percent of their plays. The next closest team using the same lineup is the Bears at 36 percent. There are two reasons: The Eagles have been healthy on offense and Chip Kelly has had great success with this group, averaging 7.65 yards a play. Only the 49ers (7.7) and Saints (8.1) are averaging more with their most-used lineups.

Bill Davis' blitzes have become less productive with each game. Overall, the four quarterbacks the Eagles have faced have eaten alive the defense when he has sent extra rushers. They have completed 43 of 66 passes for 455 yards and three touchdowns against blitzes on 70 on 187 drop-backs. The Eagles did have one interception and three sacks.

DeSean Jackson, who went over the middle very little over the last two seasons, has had great success in that area of the field this season. The wide receiver has been targeted 11 times over the middle, catching all 11 passes for 197 yards and a touchdown. Jackson has been targeted four times on the left and has caught every pass for 43 yards. His catch rate on the right, though, is much lower. Jackson has pulled in only 6 of 19 targets for 153 yards and one touchdown.

jmclane@phillynews.com

@Jeff_McLane