WORCHESTER, MA—The YMCA is doubling the size of two of its fitness centers and building a new athletic center in Massachusetts as part of a $15 million project. The Greendale Y branch will spend about $5.5 million on refurbishing its locker rooms and lobby, adding space for youth and exercise programs and building a new fitness center. The Central Y plans to expand the size of its fitness center and retrofit the locker rooms, and the Westboro Y will add a second pool and also expand its fitness center. Work on the Glendale and Central Ys will begin in September, and the renovation at the Westboro Y will start next spring.