Is there any exercise that will help strengthen your tummy muscles?

Crunches, situps, even squats to an extent.

Your "tummy" muscles form the core of your body. They are arguably the most important muscle grouping of them all.

The simplest way to look at them is this:

Your abdominal muscles have 3 primary functions: To "crunch" the body (as in pull the chin closer to the belly button), to twist the body at the waist, and to stabilize the body as it does everything else.

So basically, while you're exercising you are using your tummy to "hold your body together" and keep it stable. This is what J_9 was talking about with squats. I've also found deadlifts to be of use in this regard.

When it comes to everything else you can do for exercising your tummy, remember that the abdomen has 2 other main functions. For my money, I focus on crunching the abdomen.

Just remember that if you're drawing your chin to your belly button, whether it's by doing a standard crunch or whatever, you're working your entire abdomen. It's an all-or-nothing response on a cellular level.

If you're bending at the waist, but your abdomen isn't crunching, then you're probably using your hip muscles as the prime mover, and the abdomen isn't getting the full results.

Chin to belly button = Good