Lately we've been seeing Reese Witherspoon throwing the softball around, both preparing for a movie and playing with her kids. Even if you don't have kids of your own, coaching a youth team can be a great way to get in shape and feel good at the same time.
Even though you're not actually on the team, you'll run around plenty when trying to keep a team of teens or kids in check. You might want to try coaching a sport you played in high school, but you can also sign up to help coach a game you've only played recreationally. Many local teams can always use coaches, even if they aren't super experts.