Jose Mourinho and his Manchester United squad went straight to the club's training ground for a two-hour session after arriving back in England from China on Tuesday.
The cancellation of Monday's International Champions Cup clash with Manchester City due to an unsuitable pitch in Beijing meant Mourinho wanted a work-out for his players, and he put them through their paces between 0630 and 0830 local time.
Afterwards, the Portuguese hailed the players for their commitment so soon after an 11-hour flight.
Mourinho told the club's official website: "They are a great group of boys and the intensity of the session shows they are very professional in their outlook."
United's next pre-season friendly sees them go to Gothenburg to face Galatasaray on Saturday before returning to Old Trafford for Wayne Rooney's testimonial against his former club Everton on August 3.
They then take on champions Leicester City at Wembley in the Community Shield on August 7 before opening their Premier League campaign at Bournemouth a week later.