Please note: This is a companion version & not the original book.Sample Book Insights:#1 The core is the main link between the two extremities of your body: your legs and your trunk. It is the basis and support from which any movement gains momentum. If you want to achieve any of the more advanced bodyweight movements, you must work your core.#2 Working your core will not only prevent back pain, but it will also limit injuries. By working your core, you will make your bones stronger over time.