ENGLEWOOD, Colo. -- It is a riddle with an oh-so-elusive solution.
Why can't teams win on the road?
NFL teams travel on chartered planes with plenty of leg room and the best of planned menus. They stay in the finest of hotels on the nicely appointed lobby circuit, with police escorts in front of smooth-riding motor coaches. They don't stand in security lines at the airport on Thanksgiving break. They don't sit in traffic.
And they don't win a lot.
Just one team in the league -- the New England Patriots -- has a winning record on the road in each of the previous five seasons. Since the start of the 2008 season -- 10 seasons and two games -- just eight teams have winning records on the road. A ninth is .500.
"I don't know every reason why," Denver Broncos linebacker Von Miller said. "I always feel like we have that mindset and we're ready to play. You always have to win your home games, your division games, and if you're going to be that kind of team we all want to be, you have to win on the road. It's just hard sometimes."
The Broncos (2-0) will make their first road trip of the season this week, heading to Baltimore for a 1 p.m. ET kickoff, or 11 a.m. Denver time. The Broncos were 1-7 on the road last season.
"You can't have that," linebacker Brandon Marshall said. "In the seasons we were in the playoffs and went to the Super Bowl, the road was just another thing we handled without worrying about it. Worry about how you play, you know. Worry about how your prepare. Don't worry about where you play. We love to be at home in front of our fans, but the team that handle those other eight [games] the right way are there at the end. You have to win on the road."
What makes a team successful on the road?
"Quarterbacks, man," Broncos cornerback Chris Harris Jr said. "I think a lot of those teams have quarterbacks. Start with [Tom] Brady."
He's right. The eight winningest road teams over the past 10 seasons -- Patriots, Steelers, Cowboys, Eagles, Falcons, Broncos, Packers and Colts -- have had The Guy at quarterback for much or at least part of the past decade. Brady's Patriots (.679 road win percentage) top the group. Peyton Manning contributed to the efforts of two teams on that list: the Broncos and the Colts.
However, other factors abound. Many in the league have focused on the sleep habits of their players and coaches, both at home and on the road. Last week, Oakland Raiders coach Jon Gruden said his team was using sleep bracelets and all that "humankind has to offer" to prepare.
Kenneth Wright, an integrative physiology professor at the University of Colorado's Sleep and Chronobiology laboratory, and other researchers at the school have done extensive work with the "body clock" or "circadian clock." That's the internal clock that essentially tells your body when to sleep and when to wake up.
Researchers can track it by measuring the amount of melatonin circulating in a person's blood at a given time. In a good sleeper, melatonin levels rise a few hours before bedtime, stay high through the night and settle back down to daytime levels when a person is poised to wake up.
If your body clock doesn't match day and night hours, it can cause grogginess and other health issues. Wright and University of Colorado researcher Christopher Depner have authored a study that showed that even one all-nighter can alter levels and "time of day" patterns of more than 100 proteins in the blood, including those that influence metabolism, blood sugar and energy.
Wright said it can be an issue for people who suffer from jet lag or have shift work as part of their jobs.
Broncos coach Vance Joseph spends "a lot of time, a lot" thinking about how the team travels. In his first season, the team left on Fridays for road trips with earlier kickoffs, something John Fox also did as Broncos coach. But this season he elected to have the team leave on Saturdays for all of the trips "to get our best work in here at our own facility before we go."
"It's a natural advantage for the home team. When you travel, you're down three points, I think, before you ever walk in the stadium," Joseph said.
"Teams are more comfortable, the crowd noise -- that's huge for an offense. But really, it can affect you if you let it, so you can't let it.
"You have to do whatever you can to help the guys, and then you have to ignore it at some point and go play. If you're a good team or a team that's going to compete for the playoffs, you go play when it's time."