"He goes to a boxing class at least once a week near his home and is by far the oldest in a group of about 12," said a source.
"He is usually quite morose but cheers up enormously during his boxing sessions."
The actor, who has won two Golden Globes for House, has spoken of the toll of his tough work schedule – and the fact that he so rarely sees his wife Jo, 51, and their three children, who have remained at the family's London home.
One of the few things which lifts his mood is boxing.
"It is fascinating," he said. "I swank around thinking I am a big cheese, but you do not feel like that when you are in the ring with a chap who knows what he is doing."
I think he looks great and if it is helping him deal with being apart from his family then more power to him. I would pay to see him in a ring!
