MUSCLES ENGAGED Abdominals The abdominal muscles (abs) provide movement and support to your core area. The deeper and closer to the spine the particular abdominal muscle is, the more effect over body posture it will have, and this often contributes significantly to a healthy back. Equipment Used Bosu The BOSU balance trainer stands for "Both Sides Utilized" and is most often used for balance training, various athletic drills and aerobic activities. Exercise Instructions Step 1 Start in a modified push-up position over top of the Bosu with your shoulders lined up over your hands, one leg placed between your arms and your core engaged. Step 2 Keep your hips lowered and your core engaged and drive your knees in towards your chest alternating between legs. Step 3 Continue driving your knees toward the center of your chest until the appropriate number have sets have been completed or the recommended time has elapsed.