People tend to refer to the abdominals and the core synonymously, but this is a common mistake. While the ab muscles consist of only four groups of muscles, the entire core consists of 11, which means that strong abs don’t necessarily account for a strong core. Why choose to work the core over just the abs? ‘A high functioning core leads to a better-looking core’, says Allison. Instead of crunches, which only work your rectus and can actually shorten it, causing pain and injury,  incorporate plank holds, squats and mountain climbers, which will work all the major muscle groups connected to your core.