The "Princess of Pop," who turns 39 today, regularly showers her 20 million or so followers with pics and videos of her intense gym sessions and somehow manages to look absolutely incredible in all of them.
Her "Hit Me One More Time" heyday may have passed, but the pop icon can still play sold-out shows all over the world. That relentless workout regimen surely helps her power through performances.
Needless to say, no one's wondering how this mom-of-two has the body of model nearly half her age.
Enjoy Brit's hottest fitness moments in the gallery above, and see all of her fiery workout clips below: