And now we know why.
The 35-year-old was busy competing in the Half Ironman triathlon in Haines City, Fla., and it was all for a good cause.
"If you voted for me or #GOTG for the #MTVMovieAwards that's really awesome of you, I appreciate the support. Sadly I will be missing the show," he wrote on his Facebook last Tuesday. "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," he further explained. "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."
The triathlon was clearly no walk in the park, consisting of a 1.2-mile swim, a 56-mile bike ride and a 13.1-mile run. But Chris completed the course in 7 hours, 4 minutes and 52 seconds.
Pratt has been dedicated to his fitness after impressively shedding 60 pounds to get in action hero status for last year’s Guardians of the Galaxy.
"I have more energy," he told Esquire last August about the benefits of being in-shape. "I sleep better. My sex drive is up. Blood's flowing. I'm less susceptible to impulse. I'm in a different mode."
Check out the video below to see Chris doing more good deeds with his pal Chris Evans, when the two visited Christopher's Haven -- an organization that provides a place for families of children being treated for cancer in nearby Boston hospitals -- after the former Parks and Recreation star lost his Super Bowl bet!