USAF ACADEMY, Colorado – San Francisco 49ers Tight End George Kittle played one NFL game at a significant altitude.

Kittle’s only trip to a mile high came on September 25, when the Niners played the Denver Broncos. His recollection of how the altitude in Denver – 5,195 feet – affected him was that he was “a little out of breath”, but he also noted that he was still returning to football form after his groin injury.

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When the Niners travel to Mexico City – 7,503 feet high – for a Monday Night Football game with the Arizona Cardinals at Azteca Stadium (8:15 pm ET, Sportzshala/Sportzshala+/ABC), Kittle did what he often does, when he has a question: he called the Kansas City Chiefs a tight end Travis Kelsey For advice.

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Kelsey plays in Denver every year and had 92 yards and a touchdown against the Los Angeles Chargers in 2019 when they played in Mexico City.

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“He said the height was just tricky,” Kittle said. “He plays in Denver every year too, so he said it’s definitely a big change from what they’ve played before… I know it’s going to be something.”

Kittle wasn’t the only 49 rider who expected height to be an issue. In fact, as soon as the NFL announced the Mexico City matchup in the spring, the 49ers, led by head of player health and performance Ben Peterson, began looking at options to try and mitigate the effects of the height.

10 NFL games were played in Mexico City, four in the regular season. The teams that preceded the Niners and Cardinals had two views on acclimatizing to altitude: as early as possible or as late as possible.

In some ways, Monday night’s game will be as much a battle of scientific philosophies as a football one.

On Peterson’s recommendation, the Niners took the early route, arriving in Colorado on Tuesday to practice Thursday, Friday and Saturday at the Air Force Academy – at 6,621 feet in a football stadium – and acclimatize.

The 49ers will head to Mexico City Sunday afternoon, hoping their time in Colorado will give them an edge.

“You want to practice at that altitude because the more days you spend at it, the more your body gets used to it,” Shanahan said. “So hopefully that will make things easier for us on Monday night.”

The Cardinals took a different approach as strength and conditioning coach Buddy Morris opted for a modified program that included exercise bikes and lifting masks for the Cardinals to use at their training facilities. They will arrive in Mexico City on Saturday.

“We felt like the program we could create here for all the high altitude training was really good and wouldn’t break our routine,” said Cardinals coach Cliff Kingsbury. “They have been doing this for the last two or three weeks. All of our guys have tried to prepare for this, but I know it will be a problem either way, whether you do it or not.”

However, acclimatizing to altitude is not as easy as simply spending time at high altitudes.

It takes about three weeks to fully adjust to altitude, according to Inigo Sun Millan, research assistant professor in the Department of Physiology and Nutrition and School of Medicine at the University of Colorado at Colorado Springs. That doesn’t mean the 49ers can’t take advantage of a week in Colorado ahead of Mexico City.

“That’s not enough time to fully adapt to the altitude,” Sun Millan said. “That’s enough time to at least not suffer from the effects of altitude.”

According to Sun Millan, even semi-acclimatization can only happen if the 49ers take the right steps. For 27 years he has worked with many athletes, including Olympic medalists and Tour de France winners, studying the effect of height on athletic performance.

As Sun Millan explains, the problem with acclimatization is not the amount of oxygen in the air. The real problem comes from barometric pressure.

Under normal conditions at sea level, the weight of the atmosphere can help bring oxygen into the bloodstream, which nourishes the muscles. In a place like Mexico City, the barometric pressure is lower, resulting in a drop in oxygen saturation.

Athletes may find it difficult to breathe at altitude due to reduced blood oxygen levels. In their study, Sun Millan and others estimate that for every 1,000 feet above sea level, someone loses 2% of their ability to use oxygen, and the subsequent time to feeling exhausted is about 4% faster.

This means that in Mexico City, the Nines and Cardinals will be able to consume about 14% less oxygen and reach exhaustion about 28% faster than at sea level.

The body has built-in adaptations to help in the form of an increase in red blood cells, which Sun Millan calls “oxygen taxis” so that there are enough of them to deliver the right amount of oxygen to the necessary tissues in the body.

However, the key to getting the Nines to work is to not push yourself too hard during this week. San Milan said overtraining is typical for athletes trying to adapt to altitude, but they should really spend the first week with little physical activity.

Shanahan said Monday that the Niners won’t be making major changes to how they train, but they didn’t practice until Thursday despite arriving in Colorado on Tuesday.

“That’s where there’s a double-edged sword in such a short period of time,” Sun Millan said. “In one week, you can adapt to some extent. But then again, looking at the possible side effects, you will see players not sleeping well, they may not recover well. Training needs to be significantly changed.”

In addition to your training regimen, two other key factors in altitude adaptation are sleep and nutrition.

Sun Millan said that when he works with athletes, he implements a modified meal plan in the first week that includes adding about 30% more carbohydrates and protein to their diet to maintain energy levels.

The task of the Nine is not only to make sure they do everything right, but also to manage so many players at the same time. While San Milan can track four or five athletes at the same time, doing a blood test every five to seven days, the task is more difficult for a roster of 53 people.

In terms of sleep and nutrition, Kittle said there is a humidifier in every room at The Broadmoor to humidify the air, and there is an emphasis on drinking plenty of water and eating “as much as possible.”

This week the Nines also got a glimpse of how the speed of a soccer ball can increase in less dense air, something widely shared. Brandon Aiyuk noted on Thursday.

Responses from players this week have been that the altitude hasn’t been “too bad” on the training ground, although it’s felt the most when “playing together” meaning it can be difficult to get over long commutes on Monday at both sides.

For their part, the Nines seem happy with the decision to get a taste of the heights in Colorado, even if it comes with the low temperatures and snow.

“It’s good that we’re doing it now, so when we get to Monday it won’t be a shock.” – Midfielder Fred Warner said.