Britney Spears hit the gym in Calabasas, CA, yesterday, which she twittered was her final day of rehearsals for her upcoming Femme Fatale tour. Britney tweeted, "So electric! This is going to be the best show of my career." The Femme Fatale tour kicks off in Sacramento on June 16, and on Tuesday she announced European dates in September, October, and November. In addition to all her workouts and dance training, Britney has gotten in some great onstage practice for her racy performance with Rihanna at the Billboard Music Awards last month. Britney also recently shot her video for "I Wanna Go," which is already her third single off the hit album. Britney will have the support of her man, Jason Trawick, when she hits the road, and says she's excited to be able to bring her boys, Sean Preston and Jayden James, with her for some of the fun as well.