This article lists three movements that you can try and switch things up to challenge your body.
You will start by laying on the floor, then you will raise your shoulders off of the ground along with your feet. Finally you will raise your arms above your head, and make sure to keep your core engaged the entire time. Hold this position for as long as you can, slowly building up the time.
While lying on the ground, raise your legs straight up you will slowly lower them to one side, back to the middle, and then to the opposite side. Try this movement out with kettlebells to start, when that gets too easy up the intensity by stabilizing your core and body with no support of the kettlebells.
Once again you will be lying on your back with your shoulders and legs off of the ground. Keeping your arms long, back in a neutral position, and knees in a 90 degree angle you will bring your knees and chest closer together. Make sure to remain strong in your abdomen the entire time and do not round or arch your back.
In all, it is good for our bodies to change it up a bit and challenge it with a different type of stimulus. Routine is great but sometimes it needs to be broken in order to continue to see progress with your goals!