With only four weeks remaining before England's opening group game of the 2014 World Cup the looming prospect of playing in one of the most extreme environments ever experienced in World Cup history should be at the forefront of manager, Roy Hodgson's, mind. England will meet Italy in the Amazonian capital of Manaus at 6pm on 14 June for what is expected to be a crucial game in deciding the fate of England.
This opening game may prove to be more than just a game of football; it could be a game of survival as temperatures regularly exceed 31ºC (90ºF). But it is not only temperature that will conspire to diminish the performance of the English players, humidity, temperature's ugly brother, will be a key factor. Manaus is in the tropical rain forest region with humidity exceeding 80%. Whilst the temperature will be falling for the 6pm kick-off, the humidity will be rising leaving the players feeling like they're playing in a thick, hot soup!
Why is humidity such a big deal? Humans are homeotherms who tightly control their core temperature within a few degrees to optimise performance. From a normal core (body) temperature of 37ºC we become hyperthermic with just a 3ºC rise leading to a potential fall in performance. Once core temperature starts to rise above 42ºC, just a 5ºC rise, we start to damage cells and enter the danger zone where heat injury and heat stroke are real health issues.
In addition to the significant amount of heat produced during exercise, that's why we get hot and sweaty at the gym! The environmental conditions play a major role in controlling body temperature. The body's primary defence against rising temperatures is sweating however; the key to loosing heat is the evaporation of this sweat and herein lays the problem with humidity. As humidity rises sweat fails to evaporate and the body can no longer control temperature leading to overheating. We've all experienced this, when, instead of evaporating, sweat beads and runs of the body in humid conditions. The double whammy here is the loss of body fluid from excessive sweating as the body desperately tries to control core temperature leads to dehydration which further effects performance.
So what can be done about it? In a word, 'acclimatisation'. The human body is a wonderfully adaptable machine that, given time, is able to bring about change in a variety of systems to reduce the negative impact of the environment. Training in the heat provides the necessary acclimatisation to enhance the English player's chance of playing at their best. But, it doesn't happen quickly, and England will need to act early to ensure optimal adaptation. Traditionally, international teams have used strategies involving 10-14 days of heat exposures however; it may be possible that the same results can be achieved in a shorter time period for some individuals. The important issue here is individual responses. Not all players will respond in the same way or at the same speed.
There are also strategies England can employ pre-game and during-game to offset the environmental impact. Pre-cooling strategies, where the body is cooled prior to competition, has been used by teams including British Cycling to great success. Ensuring full hydration pre-game and providing hydration during the game will reduce the heat stress and, combined with cooling at half-time, a strategy used by other international teams, may off-set the impact of the heat in the second half.
In addition to physiological adaptations, players can adapt their technical and tactical play to reduce the impact of the heat on game performance. The major concern here is that Italy, as a nation, used to much higher temperatures than those experienced in England, will have a tactical advantage.
In short, England has got its work cut out for the first group match. Ensuring optimal acclimatisation leading into the game is the cornerstone of optimal physical, tactical and technical performance. Combined with an early arrival in Manaus and a clear heat-coping strategy for the game, England will be able to reduce the impact of the extreme heat and humidity and provide the best possible opposition for one of the best teams on the planet. Get it wrong and it could be a sweaty mess!
Professor Greg Whyte OBE is speaking at the Cheltenham Science Festival on 6 June 2014 in a session entitled 'World Cup: Coping in the Amazon'