Ground-up developers and owners evaluating value-add projects should consider bulking up their fitness amenities to support a wide range of active lifestyles. — By Sarah Yaussi, National Multifamily Housing Council (NMHC) — The health and fitness industry has undergone tremendous transformation in recent years. Specialized fitness centers like CrossFit gyms and spin studios have challenged traditional fitness centers as the workout destination of choice for many. TRX straps, kettle bells and resistance bands have claimed real estate on the weight-room floor. And the growth of on-demand classes and in-home gyms …