Chris Wolston in Nature:
Albert Einstein mastered the violin. Richard Feynman banged bongos. Following in the tradition of multi-talented physicists, Federica Bianco likes to take a break from her research to punch people in the face. Bianco, an avid boxer who is also an astrophysicist at New York University, flew to Richmond, California, for her first professional bout in April. It did not go well for her opponent. Bianco pinned her competitor to the ropes with a flurry of punches and did not let up until the referee called the fight. It took just one minute and twenty seconds. “I didn't want to stop, but she was taking too much punishment,” Bianco says.For Bianco, boxing is not just a hobby; it is a total mind-and-body escape from her work. “As a scientist, I'm thinking about all sorts of things all the time,” she says. “The ring is quiet. You get tunnel vision. The other person is trying to take off your head and you have to deal with that.”
There's even a bit of evidence of a correlation between professional excellence and excellence in a leisure pursuit:
There is plenty of evidence that scientific research and leisure pursuits can coexist. A study published in 2008 found that Nobel prizewinners were more likely than other scientists or members of the public to have long-standing hobbies. Notably, the prizewinners were about 1.5 times more likely to actively pursue arts and crafts than were members of the US National Academy of Sciences (R. Root-Bernstein et al. J. Psychol. Sci. Technol. 1, 51–63; 2008). For this sample, hobbies turned out to be better predictors of Nobel-level greatness even than reported IQ, which does not vary much between 'top' and 'average' scientists.
Why? Obviously, that's how the mind works. Unity of Being.