Celebrities including Jennifer Aniston, Jurnee Smollett, Jessica Alba and George Takei are pointing to lifting weights as the single biggest change they have made to their fitness routines. Their message is that strength work builds muscle, protects bones and delivers confidence at any age. “Strength training has made the biggest difference for me,” she said, adding that trainer Dani Coleman keeps her “getting stronger.” Related: How Jennifer Aniston Stays Fit and 'Unlocks New Levels of Strength' at 56 Jennifer Aniston has a refreshingly simple approach to staying fit: keep moving. She credits martial arts, gymnastics, dance and strength training from her Dark Angel days for her athletic build.