Marriage to Scarlett Johansson isn't slowing down Ryan Reynolds. In a blog posted on thehuffingtonpost.com, Ryan reveals that he's running the New York City Marathon in tribute to his father and actor Michael J. Fox, who are both stricken with Parkinson's disease. "A year and a half ago, I had the privilege of meeting Michael. Like so many before me, I found it impossible not to be touched by his story of overwhelming strength, passion and relentless commitment to help those afflicted with this insidious disease," writes Ryan. "The man is inspiration exemplified. In a moment of extremely poor judgment, I offered to do something big for him — I offered to compete in the New York City Marathon. Which was, well ... dumb." Ryan jokes, "It's my hope my own goal of becoming the first person in history to sob uncontrollably for 26.2 miles straight may inspire you to give something, too."

To donate to Ryan's cause, click here.