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Pity the teams who must climb into the Rocky Mountains and meet the Broncos on a field more than 5,000 feet above the sea.

Few stadiums provide so big an advantage for the home team — or so inhospitable an environment for visitors. Since the mid-1960s, the Broncos have won over two-thirds of their regular season home games, and fully three-quarters of their home playoff games.

If the Patriots are going to buck those odds and advance their quest for a fifth championship, they'll have to overcome not just the formidable Broncos defense but also the rarefied atmosphere of Sports Authority Field, where the ball travels farther and the thin air forces unaccustomed lungs to gasp for breath.

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How hard is it to play football a mile high?

Denver players are used to the heights, so for them it's just another field. But for opponents, it's a whole other story. Visiting teams don't have the time to acclimate to the altitude, leaving them short of breath and, often, short on points.

The basic problem is that as you climb into the skies, the air gets thinner. And while the 5,280 foot elevation at Sports Authority Field is more medium-altitude than high-altitude, it's enough to make breathing more difficult.

At that height, not only do you take in less oxygen with each breath, but your body has a harder time moving that oxygen from the lungs into the bloodstream.

To compensate, your heartbeat quickens, and you start breathing more rapidly. Which is mostly fine, if your plan for the day is to visit the aquarium or botanic gardens.

But if regular breathing is already a strain on the body, imagine how difficult exercise must be. With lungs and hearts struggling to capture enough oxygen, endurance athletes can't push themselves quite as hard as they're used to. That's as true of football players as it is of distance runners.

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Over the course of days, or weeks, athletes can adapt, but the rigors of the NFL schedule generally ensure that only the Broncos have the time to make this adjustment.

Does this really give the Broncos a bigger home field advantage?

It seems to. Few teams do as well at home as the Broncos. Across the NFL, home teams tend to win about 57 percent of the time. The Broncos do far better, winning 68 percent of their home games since the beginning of the Super Bowl era in 1966. That puts them at the very top of the list, in an effective three-way tie with the Steelers and Ravens.

It's even more striking if you compare the Broncos home-field record against their performance on the road. There's a huge gap, second only to the Ravens. And this tells us that the Broncos aren't winning because they're exceptionally good — if that were the case, they'd win on the road too. They win at home because being at home helps them win.

And this goes double for the playoffs, where the Broncos have won 16 of 21 home games — and just 3 of 12 on the road.

Winning percentage at home
Denver Broncos, playoffs
76%
Denver Broncos, regular season
68%
All NFL teams, playoffs
67%
All NFL teams, regular season
57%
SOURCE: Evan Horowitz

Doesn’t high altitude also affect the ball?

It doesn't necessarily make the ball feel more inflated or deflated — just to get that out of the way.

But footballs thrown or kicked in Denver do travel farther. That's one reason three of the five longest field goals in NFL history were kicked in Denver, including a record-setting 64 yarder in 2014.

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It's not clear, however, that this gives the Broncos any substantial advantage.

For instance, while it's true that Tom Brady's deep passes might fly a bit farther than expected, the effect is fairly small — and not unlike other inconveniences that quarterbacks are always adjusting to, such as wind or rain.

Likewise, Stephen Gostkowski's kicks will get the same boost as Brandon McManus's. And Gostkowski is already the superior kicker, with a much higher success rate. Being in Denver merely increases the odds that he'll be able to hit from 60+.

What does all this mean for Sunday’s game?

The biggest worry for Pats fans should be the fatigue that comes with playing at Denver-level altitudes.

New England players are likely to tire more quickly than usual, and need more regular breaks to catch their fleeting breath. This could be a particular problem on defense, if Peyton Manning is able to push the tempo and keep the Patriots from rotating players in and out.

Nonetheless, despite the thin air and the Broncos' dominant home-field history, New England remains a slight favorite.

And if they can pull off the victory, not only would the team be headed to their seventh Super Bowl since 2002, but it would also allow them to escape the lung-taxing air. This year's Super Bowl is being played at Levi's Stadium in Santa Clara, California. Altitude six feet.


Evan Horowitz digs through data to find information that illuminates the policy issues facing Massachusetts and the U.S. He can be reached at evan.horowitz@globe.com. Follow him on Twitter @GlobeHorowitz

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