MUSCLES ENGAGED Obliques Many people put a lot of focus on working their abs but forget their surrounding neighbors; the oblique muscles. Obliques serve as stabilizers, and are used in almost every physical activity. Exercising your obliques should be a very important part of your workout program. Back (lower) The lower back is often not trained because it is not visible in the mirror. If you have weak lower back muscles, there is nothing to help pull back against the spine, putting you at risk of developing poor posture (hunched over). Weak lower back muscles can also lead to lower back pain. Equipment Used Stability Ball A stability or exercise ball is a ball constructed of soft elastic and filled with air until firm.Most stability balls range from a diameter of approximately 35 to 85 centimeters (14 to 34 inches). Exercise Instructions Step 1 Start with your feet anchored against a wall. Position your body onto the stability ball so that it is underneath and supporting your hips. Keep your body turned sideways and have your hands placed beside your head. Step 2 Keeping your lower body locked into postion, curl up to the wall using only your obliques and core muscles. Step 3 Lower yourself back down to the starting position, stretch out your side and repeat action.