Hi @maggie25. I've been told that both flexion and extension are risky as they put extra load on the spine that can lead to fragility if done too often. Ideally, we want to build strength and endurance in the muscles that support the spine, so we can hold it in "neutral" position while doing everyday activities as well as sports. The approach is suggested by Stuart McGill, PhD, a Canadian researcher who studies biomechanical forces on the spine. He wrote book called The Back Mechanic. I found the book useful for learning how to move more safely. Perhaps you would like it, too.