Yahoo Sports How do footballers play in very cold conditions?
Football clubs always strive to keep their performances consistent - regardless of the conditions.
But when it's cold, they have to be particularly proactive to help players perform at their best.
How do teams acclimatise to the cold?
For European games, clubs might travel to countries that have much lower average winter temperatures than the UK.
Chelsea's Conference League match against Astana in Kazakhstan, for example, was played in temperatures of -11C.
To acclimatise, teams will endeavour to train in situ the day before a game to experience conditions as close as possible to those they may face on match day.
Do players warm-up differently in the cold?
It's a matter of tweaking - rather than a complete overhaul.
Warm-ups raise a person's core temperature, and increase blood flow to the muscles - priming the body for activity.
Geoff Scott - former head of medicine and sports science at Tottenham Hotspur - told BBC Sport teams would usually do pre-activation in the dressing room, regardless of the conditions. Players will go through a series of mobility and muscle-activation exercises, using foam rollers and resistance bands.
However, the length of pre-activation (usually about 20 minutes) might be extended before players go out to play in particularly cold conditions.
The on-pitch warm-up time will stay largely the same.
Scott said: "Whether it's zero degrees or -10C, players won't notice much difference - the warm-up is very important regardless."
What do players wear in the cold?
Layering is key. Base layers and undershorts are often worn, but these must adhere to the International Football Association Board's (IFAB) kit regulations around safety and consistency with team colours.
Our extremities - such as hands, feet and the head - are particularly vulnerable to the cold.
Heat can easily be lost due to the poor insulation and surface area of these extremities, and it can also explain why some players wear gloves but also short-sleeved shirts.
Some players have a not-so-secret weapon up their sleeves. Or - perhaps more accurately - in their boots.
Players sometimes make use of toe-warmers. These are like hand-warmers you can buy off the shelves, which produce heat through a chemical reaction once activated.
What about the subs?
After warming up with the team, substitutes will cool off quickly when sitting on the bench. When muscles get cold, and are then put under strain, the risk of injury can shoot up.
Scott said that in colder conditions, substitutes would be instructed to warm up more regularly than usual.
While sitting on the bench, lots of layers will go on - club jackets, snoods, hot-water bottles and blankets.
Managers will also be briefed prior to the game to give medical staff more warning than usual if they are intending to make a substitution. This allows the substitute coming off the bench more time to warm up, and to take off all their layers.
Team physios may be instructed to slow down the changeover process if an injury occurs on the pitch, to allow the substitute taking the injured player's place that little bit extra warm-up time.
What about the goalkeeper?
Explosive movements followed by stationary periods is very much the nature of a goalkeeper's job. But that makes them particularly vulnerable to injury when the temperatures fall.
During the less active periods of the game, muscles can get cold, limiting the range of movement and making it easier to pick up strains or tears.
Scott says in cold conditions, the performance team will instruct the goalkeeper to do more running in the box during periods when the ball is at the other end.
The aim is to keep the muscles warm and primed.
Are there any nutrition considerations?
Emma Tester, who spent three years as the head of nutrition at Tottenham, says achieving a high carbohydrate intake is always the priority - regardless of the conditions.
However this can become more challenging in more extreme environments.
"If you're cold, you shiver or do extra activity to keep warm," said Tester. "This causes a higher glycogen demand, and the body is reliant on glycogen as a fuel source. When you're in these environments, your body is working much harder."
Carbohydrates replenish the glycogen stores in the body.
Tester told us players on the bench should fuel as if they are playing a full 90 minutes. Especially in cold temperatures, players will expend energy shivering to keep warm, and might not always be aware of the energy stores they're using even at rest.
Players will have a combination of carbohydrate-based sports drinks, energy gels, bananas, foods that provide a quick energy release and are easy to digest
Another consideration is dehydration, which is even a risk in colder conditions.
Tester says players might not take on as much fluid because they don't realise they have still lost a lot of water in sweat, despite the temperature.
When you're dehydrated, your body has to work harder to transport nutrients and oxygen around the body. This can affect cognition, so passing accuracy, skill execution and sprint speed can be reduced.
So, substitutes waiting for the call will be watched closely by team nutritionists to ensure they are taking in enough carbohydrates and fluid in colder conditions.
Tester believes we will see more research in the next few years looking specifically at how colder conditions can affect elite football players' performances, particularly in light of the increase in extreme weather events in the UK.
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