When football players get high it’s tough to determine how they will perform

If the Rams are curious about their trip to Mexico City, where they will face the Kansas City Chiefs next week, they might want to check with Eric Wynalda.

A star on the U.S. men’s soccer team through the 1990s, Wynalda has personal experience with sprinting up and down the field at Estadio Azteca.

His memories of playing in the stadium can be condensed into a single word: “Horrible.”

Let that be a warning to the Rams as they prepare for next Monday night’s game, where the elevation of about 7,300 feet and the often smoggy conditions could be every bit as challenging as their formidable opponent.

“For a physical game like football, it’s a big deal,” said Inigo San Millan, director of the Sports Performance Program and Physiology Lab at the University of Colorado. “Your body is going to say, ‘What the heck is going on? This is not my environment.’”

The Rams hope to ease the shock by practicing all week in high altitude at the U.S. Air Force Academy in Colorado Springs, but research suggests that not everyone’s body adapts in only seven days.

“That’s the risk they are taking,” San Millan said. “And they could pay a price for the rest of the season.”

This will be the third consecutive fall that the NFL, looking to market its brand internationally, has scheduled a game south of the border. Last year, the New England Patriots were 33-8 winners over the Oakland Raiders in the Mexican capital.

Marquis Flowers noticed the difference playing both linebacker and special teams.

“I’m not going to lie, there was one drive when there were a lot of plays,” said Flowers, a former Patriots linebacker who spent the early portion of this season with the Detroit Lions. “You definitely start feeling it.”

Contrary to popular belief, the air we breathe contains about 21% oxygen regardless of altitude. The true culprit is barometric pressure.

At sea level, the weight of the atmosphere helps push air into the lungs, pressing oxygen molecules into the bloodstream where they can feed working muscles.

In thinner air up high, the molecules are spaced farther apart and this process works less efficiently.

Through studies at their Colorado lab, San Millan and his colleagues estimate that for every 1,000 feet of elevation an athlete loses 2% of his ability to consume oxygen.

The metabolic response to this deficit increases glucose consumption and produces more lactic acid, which hampers muscle performance and causes athletes to fatigue about 4% faster.

Those numbers might not sound big, but in Mexico City — approximately 2,000 feet higher than Denver — they translate into 14% less oxygen consumption and almost 30% greater rate of exhaustion.

“The main problem is with the big guys,” San Millan said. “Both on the defensive and offensive line, they are larger, they need more oxygen and, metabolically speaking, they are not as fit as other players.”

Breathing problems and fatigue can be exacerbated by high levels of pollution in a sprawling Mexican metropolis where thermal inversions and dry months can force the government to restrict driving.

The weather next week might do the teams a favor, with forecasts calling for a chance of thunderstorms that could wash the air clean. Still, the altitude alone might impact mental acuity.

In the rush of competition, Wynalda recalls, running downfield wasn’t so awful. But between plays, he said, “you got dizzy and you felt like you were going to pass out. You couldn’t get your bearings.”

When the other team had a corner kick, for example, he and his teammates struggled to react quickly, falling a step behind their opponents as play resumed. In a football game, there are dozens of similar restarts.

“I would think the stop-and-go of it would be really problematic,” Wynalda said.

Teams unaccustomed to competing at altitude have two choices.

Last season, the Raiders flew into Mexico City the day before the game, which is what the Chiefs are doing this year and what experts characterize as a reasonable strategy. It doesn’t allow time for the body to wear down under stressful conditions, so athletes might not feel as bad during those initial 24 hours.

Wynalda recalls that when the U.S. played Mexico in 1993, he and his teammates arrived three days early and felt good during the first practice. Two days later, they were struggling and lost 4-0.

The Patriots chose to train at the Air Force Academy the week before the game. That seemed to work — they won the game — so the Rams are following suit.

As soon as the NFL issued its 2018-19 schedule, the Rams’ athletic trainers and nutritionist researched altitude performance and decided on spending a week in the mountains.

“It was just on the edge where we thought it would be good,” said Reggie Scott, the team’s senior director of sports medicine and performance.

Practicing at altitude, the body eventually compensates by producing more of the red blood cells that capture and transport oxygen molecules. But this process can take one to two weeks, researchers say, so the Rams are walking a fine line.

If the team doesn’t adapt in time, the ramifications could extend beyond an uneven performance Monday night.

A high-altitude environment can cause the body to break down muscle, even within the space of a single week. Players could return to Los Angeles fatigued to a degree that lingers through the bye week and into games against the Detroit Lions and Chicago Bears in early December.

“It can really put you in a hole,” San Millan said. “I’ve seen it many times with athletes.”

So what should teams do?

Marathon runner Meb Keflezighi, who has a long history of training in the mountains, said that when it comes to acclimatization, patience is a virtue.

“You definitely have to respect altitude,” said Keflezighi, who won a silver medal at the 2004 Athens Olympics. “If you pace yourself, you will be stronger.”

The Rams should treat this week almost like recovery time, San Millan said, with players limiting exertion, staying hydrated in low humidity and devoting extra time for rest because altitude can disrupt sleep. It might help that the team adheres to an unconventional regimen even under normal circumstances.

Players rehab and sometimes run Monday, take Tuesday off and limit Wednesday to a couple of walk-throughs. Thursday practice is followed by a short workout Friday and another walk-through Saturday.

Scott and his colleagues will monitor hydration and nutrition, and will place humidifiers in each room. The players have been instructed to take precautions as they adjust.

“Science, man,” cornerback Nickell Robey-Coleman said. “Put your trust in science.”

The Rams probably won’t be in Colorado Springs long enough to develop the enriched blood that runners and cyclists get from training in the mountains for weeks.

Performing well at Estadio Azteca — and returning to Southern California without lingering effects — might be the best they can hope for.

“It’s a very difficult place to play,” Wynalda said. “I don’t know if it’s a healthy thing to do.”

Times staff writer Gary Klein contributed to this article.

david.wharton@latimes.com

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Staff writer Gary Klein contributed to this story.