CORE STRENGTH. There is nothing more important than having a strong core. The entire TRX class focuses on stabilizing your core midlline muscle groups. Don't let that fool you - you will work ever inch of your body. This is by far one of the most demanding 50 minute classes you will ever take. You will sweat, you will burn, you may even cry a little. After taking this class you will not only be toned, but your core will be strong enought to back it up.