Chris Pratt missed the MTV Movie Awards to take part in a half-Ironman triathlon.

The 'Guardians of the Galaxy' star - who was nominated for four prizes at the Los Angeles ceremony - undertook the gruelling event in Haines City, Florida on Sunday (12.04.15) and completed the 1.2-mile swim, 56-mile bike ride and 13.1-mile run in an impressive seven hours, four minutes and 52 seconds.

And the 35-year-old actor even found the time to help one of his fellow competitors when she was stricken with cramp during the course.

Erin O'Connell wrote on his Facebook page: ''You were so kind and encouraging to me when I ran next to you for a few miles on the run and and asked if I was okay when my leg started cramping.

''You did an amazing job out there Chris and have a wonderful heart and spirit. Thank you for your support of wounded warriors and you were such a great motivator for others while on the run!(sic)''

Chris admitted before the triathlon that it was going to be a ''major challenge'' but he felt prepared for it.

He posted on Facebook: ''On Sunday I'm joining former Navy SEAL Mike Day as he participates in a grueling half ironman to raise money and awareness for our nations brain injured heroes.

''The Ironman 70.3 or 'Half Ironman' is an endurance race of swimming, biking and running. It's going to be a major challenge and I've trained long and hard for it. ... I hope to help raise awareness and money for a great cause and true hero.''