Here are three body-weight core exercises you can do anywhere. No equipment is required and they provide challenging work for the abdominal, oblique, and erector spinae muscles. Descriptions and videos are provided via links to the EXRX website.
First are V-ups, advanced sit ups that require not just abdominal strength but also balance. Try holding for a few seconds before releasing.
Second are lying twists for the obliques. These are also referred to as “clocks.” They can be done with legs bent, or legs straight which is more challenging.
Last are supermans, which require lying prone and lifting the arms and legs off the ground simultaneously using the glutes and erector spinae. The advanced version also brings your knees off the ground so your entire body is balanced on the pelvis region.