Action star Matt Damon surprised onlookers at Florida's Escape to Miami Triathlon on Sunday (05Oct08) when he turned up to take part in the gruelling race.
The Bourne Identity actor joined his stepfather Jay Jones and family friend Barry Hetherington as part of a running team.
Damon sprinted 6.2 miles (9.97 kilometres) in 59 minutes and 54 seconds, and was met at the finish line by his wife Luciana Barroso and newborn daughter Gia.
After the race, he joked, "I knew I was in trouble when the old guy with the oxygen tank passed me."
Damon's brother Kyle competed in the whole triathlon and recorded a time of 2 hours, 23 minutes and 40 seconds, finishing in 27th place.
And it was his sibling who convinced Damon to enter the running, swimming, and cycling competition.
He tells the Miami Herald, "My brother talked me into it. I was doing this movie this summer, The Informant, where I had to put on all this weight, and my brother told me, 'October 5, save the date'."
And the exercise will come in handy for Damon's next unspecified project. He adds, "I've got to get in shape for the next thing I'm doing."
Damon is not the first celebrity to take part in such high-energy activities - Jennifer Lopez and Matthew MCConaughey both completed the Nautica Malibu Triathlon in California last month (Sep08), while Katie Holmes ran the New York City Marathon last November (07).