The actor is in the U.K. for the London premiere of his new film Men in Black 3, and he took time out from the promo trail to show off his sporting side during an exercise class with some of the country's fittest men and women.
The star shot hoops on the basketball court with Olympics team captain Drew Sullivan, before jokingly tackling the hurdles with Perri Shakes-Drayton. He also sparred with heavyweight boxer Anthony Joshua and attempted the long jump with Yamile Aldama.
And despite his buff image, Smith insisted he wasn't athletic until he began working out for his movie career.
He told reporters, "I've always loved sports - I love basketball and I love boxing. But I've never considered myself an athlete. I was a little bit goofy until I was about 14 or 15. The first time I ever saw myself look good athletically was in the first Bad Boys.
"(Director) Michael Bay shot me running in slow-motion and I thought, 'Hey, that doesn't look half bad' but other than that, I've never been really athletic."
Smith also revealed he would attend the Olympic Games in London over the summer (12).