A 12-year-old boy claims to have scaled the equivalent of Mount Everest without leaving his house by going up and down stairs 2,507 times in under 24 hours.
Seth Charles, from Sheffield, set himself the challenge after the virus outbreak meant he had to rethink a planned climb of Scafell Pike.
He was hoping to fundraise outdoors for a boxing training trip in the US.
Seth's mum Rachael said he started the stair climb at 05:30 BST on Tuesday and finished at 04:45 the next day.
"I was so relieved it was over. I was so tired I just wanted to go to bed," said Seth.
"My legs are pretty sore but I'm ok."
Mrs Charles, 45, said: "I just couldn't believe that he carried on going, I was just dead on my feet just being there and helping him count. But he did it."
She said the keen boxer only stopped for food and was supported by his younger sister, who kept a tally for him.
"We originally thought it would take him 10 hours, but realised we had got our maths wrong.
"They've trained him quite well at this boxing centre. They do stairs there, but they've never done that amount before."
Mrs Charles said he climbed up and down the 3.53m tall staircase in his house and by the end of the challenge, he had completed a total of 85,238 steps.
Mount Everest stands at 8,848m above sea level.
Seth, who trains at Sheffield Boxing Centre, reached the finals of the national championships last year.
He is part of a group of amateur boxers at the club who are raising money to go to San Francisco on a training camp later this year.
But it is not yet known if the trip will be rescheduled due to the coronavirus pandemic.