Jessica Biel Shows Off Her Impressive Muscles for a Good Cause

Jessica Biel is taking part in The USO’s Flex 4 Forces movement, to show support for servicemen and women and their families for Independence Day.

“Join me and @The_USO as we honor and support our servicemen and women! I hereby nominate @TheRock to join in on the #gunshow #Flex4Forces,” Jessica captioned the photo, showing off her impressive bicep! Jessica nominated Dwayne “The Rock” Johnson – who may have one of the best flexes in Hollywood.

PHOTOS: Check out the latest pics of Jessica Biel

Jessica is one of the biggest celebs to take part in the movement so far – expect to see some more throughout the holiday weekend!