Manchester United's players were introduced to a high-tech cooldown jacket before their training session in Chicago on Friday.
The club's performance department have teamed up with kit sponsors adidas to trial the cooling strategy which is expected to be used widely at the World Cup in the US next summer.
Ed Leng, United's head of physical performance, was heard telling the players they will wear the silver jackets after the warm-up and at half-time of their three games on tour as they limbered up at Soldier Field in Chicago on Friday, while first-team lead performance coach Charlie Owen modelled one for the squad.