Spring Fitness in Full Effect ... Sweat It Out With the Stars!

Fitness during spring ... is in full swing! And, American actor and singer Max Ehrich kickin' off bulk season with this fit photo!

We've got a rock-solid photo gallery of stars breaking a sweat, including studs like Mark Wahlberg, Jason Derulo, and Alex Rodriguez. And not to fret, we've got ladies in there too! Catch a good glimpse at workout babes like Kate Upton and Khloe Kardashian ...