An expert trainer says this is the one core move she gets all her clients to practice before they start strength training

A woman lies on her back performing a dead bug exercise on an exercise mat in her living room. Her left leg and right arm are extended along the floor, while her left arm and right leg are elevated.

You might have read or heard a trainer advise you to engage your core before executing a move.

But if you’ve ever been confused about exactly what that means or how to do it, then you’re not alone.