England manager Roy Hodgson had his players train in three layers of clothing at the team's camp in the Algarve to replicate the scorching conditions at this summer's World Cup.
The Three Lions' head of performance services Dave Reddin advised the squad to wear special pads underneath their tracksuit tops to allow his team to assess how they fared in the heat.
"The players wore sweat pads for part of today's training," Sky Sports News quotes Hodgson as saying. "We tested how much they sweat, how they will be able recover and what can be best done for them to help them.
"They will be analysed in terms of the extra heat we tried to generate. It is part of our process which Dave [Reddin] and his team have formed - it's about learning to be comfortable being uncomfortable.
"There are going to be uncomfortable moments [in Brazil] and you've got to learn to get comfortable with that."
England have been drawn in Group D of the competition, along with Costa Rica, Italy and Uruguay.
The team's opening match against Italy on June 14 will take place in the jungle city of Manaus, where humidity reaches as high as 80%.
