Up in the gym ... NBA player Klay Thompson slipped out of his jersey and threw on some gym attire during his time off the court. Kate Upton also worked on her fitness regime and picked up some iron and to no one's surprise, Dwayne Johnson looked swole AF and Rock-ed a pair of short shorts.

Khloe Kardashian is all about prioritizing her mental health and fitness and showed off her Klassic Kardashian Kurves ... rowing right into the new year!

And, Chris Pratt got his blood pumping with the assistance of celebrity fitness trainer Simon Waterson and made sure to snap the sweaty proof ... pics or it didn't happen, right?!