A breath of fresh air? England in peril as they hit the high ground in Mexico City

KANSAS CITY, Missouri, July 2 : The first signs may come before kickoff. A faster heartbeat. Deeper breaths. Perhaps a restless night's sleep. 

As England prepare for Sunday's World Cup last-16 clash with Mexico at the Azteca Stadium, they are confronting the reality of playing at 2,200 metres above sea level with little time for their bodies to adjust.

Thomas Tuchel's side face a different opponent in Sunday's clash - thin air - which Tim Meyer, Germany's team doctor at six World Cups and a leading expert on sports medicine, said was "quite a decisive advantage" for Mexico.

Mexico City's elevation impairs aerobic capacity because less oxygen is physically dissolved in the blood, making it harder for the body to push oxygen into the cells and delaying recovery.

In a paper published in the journal Sports Medicine in March, lead author Chris Esh of Loughborough University and colleagues including Meyer constructed the worst possible situation during a tournament.

"It's exactly this one," Meyer told Reuters. "You can do a lot in preparation, but what you can hardly do is acclimatise, or even sufficiently adapt, to altitude before you are at altitude.

"When you don't have enough time, it's really, really difficult. It will probably be the most strenuous game for the English team."

Tuchel has acknowledged the problem.

"My understanding is that we cannot adapt to the altitude," he said after Wednesday's 2-1 last-32 win over DR Congo.

"That is just a huge advantage that Mexico will have. It just takes too much time. We have only three days in between this match. It's physically just not possible to adapt to the altitude, which is quite high."

ALTITUDE IMPACT

Altitude's impact on sport is well established. Meyer pointed to the 1968