From a new tip out of Prevention Magazine - Balance on one leg to improve core muscles. (i)
I love any opportunity to work my core without doing sit-ups. Here's how it works. When your body is unstable, your core muscles engage to keep you from falling. If you concentrate on holding them tight it will be even more effective.
So how do you take advantage of this instability? Do one-legged squats or add a glute press or knee lift to your lunges. Use a Bosu ball or wobble board for squats and lunges. Stand on one leg while you do upper-body moves or hold a light weight overhead when you do lower-body exercises. I also balance on one foot while brushing my teeth, cooking, or getting ready in the morning (not a good idea while applying mascara).
Any other ideas for throwing yourself off-balance?
(i) "10 Flat Belly Shortcuts" by Alyssa Shaffer, Prevention, December 2009.