Functional training exercises are important for developing overall core strength and preventing lower back pain. (ab-core-and-stomach-exercises.com)
This will help you to develop good overall core strength and endurance. (verywellfit.com)
This exercise on its own can build amazingly strong and defined abs as well as great overall core strength so it is a must do exercise for anyone wanting to master the most difficult bodyweight exercises, having said that, it should only be attempted by people who have trained for some time and already posses a good level of overall body strength as it does have a high risk injury factor if you attempt it before you are ready. (unique-bodyweight-exercises.com)