Core exercise and core strengthening programs are important for your health. It's not enough to just do ab crunches and sit ups. To build a strong core you need to exercise a variety of muscles, from your hips to your shoulders. When these muscles contract, they stabilize the spine, pelvis, and shoulder girdle and create a solid base of support for powerful movements of your extremities. A strong, fit core helps your daily activities become easier to do and improves your performance in sports and exercise.