Two-time Olympia Figure champion Erin Stern may have retired from active competition, but when it comes to coaching her clients, and leaning into longevity, the buff beauty is as active as ever. Recently, Stern took to Instagram to share the moves that keep her bouncing through life, and best of all, no free weights are required. “Agility, mobility, bounce and core—these are the traits that we lose with age,” said the inspirational fitness figur…