The official App for FIT640. Download the app to book your classes, manage your schedule, and stay up to date on upcoming events. FIT640 is THE fitness destination in NH’s Seacoast. We don’t just burn calories, we train smarter. Our strength and resistance program SmartFit640 & cardio program BURN640 are based in science, and designed to utilize each of the 640 major muscles in the human body for maximum results. We Coach, You Win. Come feel the difference!