We're sorry, but online registration is not allowed for this activity. Group Exercise classes, Yoga & Pilates and personal training are available for full members of the facility. Please contact us during regular business hours for registration information. CORE is a 30-minute workout designed to tone your body and improve your core strength. This is a prerecorded class taught by a YMCA instructor that airs on-site at the branch. Category Exercise, Health and Wellness Location Aerobics Studio at West Chester Branch Instructor Jackie C.