Harry made the video call from his home in California.
The room erupted into laughter when the Duke of Sussex teased competitors over the time they’ve had to prepare for the Games, which were last held in 2019.
“You realise that no-one, not just you guys, no-one’s got any excuses for not being fit now,” he teased.
The event took place at a final training camp for those involved before the games take place in the Netherlands this month.
Harry also prompted laughter as he spoke to his former royal army physical training corps instructor Vic Wales.