LYNN-Anybody who wants to work off a belly full of Thanksgiving turkey and stuffing can do so free of charge Friday at the Greater Lynn YMCA.The YMCA is holding its annual Turkey Blast exercise program during which the community is invited to try out fitness classes at the 20 Neptune Boulevard facility.”Friends and the whole family are invited to come down and experience our new and old programs,” said Sharon Dobbyn, the fitness director. “Group classes are a great motivator for your post-turkey slump day.”Although admission is free, Dobbyn said the YMCA appreciates the donation of toys for its Toys for Tots drive, which has a reception station in the building lobby.The free classes begin at 10:15 a.m. with a spinning class led by Dobbyn, followed by Tae-Bo at 11 a.m., Butts & Guts at 11:30 a.m., Zumba at noon, Total Fitness at 12:30 p.m., Step at 1 p.m., yoga at 1:30 p.m., Zumba with Joseat at 2 p.m. and Barbell Pump at 2:30 p.m.