EXPLAINED: How altitude will affect England's World Cup clash against Mexico

Well, England don't have long to reflect on yesterday's dramatic win over Congo, because an arguably tougher task awaits them in just a few days' time.A round of 16 clash against Mexico, which will be played here at the famous Azteca Stadium, over 7 ,000 feet above sea level, with the topic of altitude already becoming a major talking point going into this game.

It's such a difficult game, talent -wise, I don't think they've got a player that will get in the England team.But when you're playing where they're playing with the fans and in that stadium and with the altitude above sea level, I think this is a difficult, difficult game.I think this is a heads or tails football match.I wouldn't be shocked if we didn't win this football match.If it was anywhere else in the world, I would expect us to win it.But in Mexico, I think it's a difficult game.

Right.Well, our sports news correspondent, Garen Hughes, has joined us in the studio to look at the science behind this.We're all a bit worried, well England fans are a bit worried.I'm neutral.I wish I could be more neutral sometimes.But how much of a factor is this all going to be Sunday night?

Right, I am not going to lie, this is going to be a factor.Let's break it down, Pete, what exactly the effects of altitude are for elite athletes.I will get to these, but these are four things that I've picked out.That you will breathe more, an increased breathing rate, which leads to an increased heart rate.You'll dehydrate quicker.Also, your sleep patterns disrupted, certainly in the first two or three days when you go from an altitude that is maybe more akin to what we live at, close to the sea level,

than being in excess of 7 ,000 feet where Mexico City is, where the Aztec Stadium is as well.Right.Why?When you are at altitude, there are fewer oxygen molecules in the air.So when you're breathing them in for your body to absorb them, you have fewer red blood cells.They can't absorb them.

So you're trying to breathe more.You breathe quickly to try and get more of the oxygen molecules in that you can transfer around your body.Because you're working a bit harder with your breathing and your heart rate, what's going to happen?You are going to fatigue quicker.So roughly the rule of thumb is maybe over 90 minutes or 120 minutes, your fatigue levels could increase by up to 15, maybe even 20%.I think 15 % is probably closer because the England players are really fit and it's not exactly so they didn't know.

that this was happening.They can't do everything to acclimatise, they can do very little, but they will have done what they can do, and the players will psychologically be aware of what's happening.But fatigue levels are going to be...They are going to be higher.But it doesn't mean that Jed Spence, Mark Gaye, even Harry Kane, if he gets into a sprint, that they will go any slower.Speed will not change.

Yeah.It's just the recovery after that and the endurance.That's what really the effects of altitude are.The reason I put this one in It's when you go from sort of close to sea level up to the altitude they're at, it does affect your sleep.And England are going into Mexico tomorrow, so they're going to have two nights sleep.in Mexico City at altitude where because of the dehydration risk because you need to hydrate more it also knocks on with your sleep pattern can sometimes be for a lot of people not everybody Pete but it can affect sleep patterns and what do we know for elite athletes not just England footballers but elite athletes they need their rest and recovery and if you don't get your proper rest and recovery when it comes to the 90 minutes that you need to be at 100 %

to beat Mexico if you're at 99 or 98 or 97 % well we know at this level it's the 1 % gains which get you through so that is a potential as well.What can they do to try and navigate their way through this then?Ideally have been in Mexico City for a week already.I have been to countless altitude camps with elite sports, a lot of Olympic sports, rowing, athletics.You hear they're training at altitude.

What does that mean?

Because you're actually training the body to be used to having less oxygen in the air, oxygen molecules, and getting your body to create more red blood cells.England do not have the time.for their bodies to be able to produce enough red blood cells.Two or three days there, their body is not going to adjust to the point of where, you know, a Keeley Hodgkinson or the Team GB8 rowers would have been in for that long that they could have got all the red blood cells they need.So they either should have gone in a week ago or, there's another school of thought, Pete, go in late.going really, really late.

So your body gets to altitude and it's kind of going, whoa, what's wrong here?It doesn't know, but it goes into fight mode.And you fight it through.There's a knock on those that when you leave your recovery, you're going to be absolutely knackered.But there is a school of thought, and rugby players have looked into this.Lions Tours, for example, when they played in South Africa.

They've been down at sea level, Cape Town, Durban, around the area.They've had to go to Johannesburg.They try and go in on some of the tour matches, not the test matches.Tour matches, trying to go as late as possible to Johannesburg, which is only 1 ,000 foot lower, or just over 1 ,000 foot lower.And your body just finds a way of coping.If you're in it for two or three days, your body will fight it, but then it will realize, what's going on here, and it will slow everything down.

You don't go into that fight mode.So there's a school of thought.Either you've got to be in a week before to fully acclimatise, or you get in a week before.as possible.Now, Thomas Tuchel, we know what's really good.He's just not bothered.

And I really like this about him.He knows all this is happening.He knows they're at a disadvantage.But his feeling is, just get on with it.

Yeah.

The players have a lot, a lot of heat training already in their bodies that would help them.So I think the heat and the humidity will not be the problem for us.We are used to that.We are used to that from training times and we are used to it from our prep camp in Florida.My understanding is that we cannot adapt to the altitude.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 is physically just not possible to adapt to the altitude, which is quite high.We knew that before, so this is just a disadvantage with which we will have to deal.

So, Garan, quickly, two rules of thought then.Going early, they haven't got time, or going late.What are England going to do?To be honest, they're going in tomorrow.

Right.

Somewhere in the middle.

I don't know.Listen, the thing is, it affects everyone differently.Sure.And England will have been prepared.They'll have plans in place.They're just doing this as quickly as possible.

But they're going in tomorrow.But the school of thought has either gone in a week ago or going as late as possible.OK.Well, hey, this might be a new thing.going somewhere in the middle.The other thing is, are England better than Mexico?

If they're better at football, they just beat them anyway.Yeah, fair play.Great stuff going.