Before I answer this one it’s important to know what your core actually is. We’re talking about the group of muscles that make up your trunk. From the bottom of your breast bone (sternum) to your hips (pelvis). It can even be argued that your bum (gluteals) form a part of your core too.
Now let’s deal with a myth.
Your core is not your six pack. If you want one of those, well you’ve already got it. Your six pack is purely the way your rectus abdominus looks. That’s the muscle down the front of your torso. We all have one but most of us have ours hidden away under a layer of fat. If you want to see it you should be concentrating on changing your diet (and lifestyle) so you can burn away the fat that’s covering it up. No exercise will reveal your six pack.
Before I answer the original question let’s talk about what your core actually does. It stabilises your spine and aids movement with trunk rotation while stabilising your spine … and that’s it.
So any exercise that causes instability can challenge your core to varying degrees. Even standing up works your core. Otherwise you would fall over.
The exercises that don’t work so well are the ones that you often see happening in the gym. For starters forget anything that involves lying down. Why would you start in a position where your core doesn’t need to work? Secondly ignore any exercise that only challenges a part of your core (i.e. one muscle only). Your core works best as a team so you’ll want to train it to work as a team.
So, any exercises that includes instability is a core exercise. Cross country running, walking on a beach, mowing the lawn, raking up leaves, swimming, standing on one leg, squatting. All great core exercises.
Here are a few links that will help you too: