England players have taken specially-devised digital capsules to give head coach Thomas Tuchel a better understanding of how his squad will respond to the heat at next year's World Cup finals, sources have told ESPN.
Sources say the Football Association created the pills -- which were used during England's training camp in Spain this week -- ahead of Saturday's World Cup qualifier against Andorra.
ESPN reported on Tuesday that England were using artificial pitchside tents with heaters inside to recreate the temperatures they will likely face in the United States, Canada and Mexico next summer.
Sources have now revealed that the players swallowed capsules containing digital technology before undergoing strenuous bike work to produce data. Afterwards, analysts were able to remotely scan the tablet to create a profile from -- measuring the internal temperature of a player's body, and how quickly they were able to cool down
Tuchel will then be able to determine how individuals are likely to cope with extreme temperatures as the capsule provides information on the length of time players could play at an optimum level before beginning to tire.
There are fears that at least four of the host cities could exceed the 32C (89.6F) mark which FIFA rules dictate would trigger automatic cooling breaks in each half, around the 30th and 75th minutes.
Research led by Queen's University Belfast suggested as many as 14 of the 16 stadiums that will be used could reach the 'potentially dangerous' level of 28C (82.4F)
Speaking last week, Tuchel referenced a preseason tour to the U.S during his time in charge of Chelsea and said: "It is important to see matches now in America, and in Miami at three in the afternoon.
"The actual experience is for the players, but I have done preseason there in Orlando and I will be very surprised if we do not suffer. Suffering is one of the headlines for this World Cup."