A trainer says this bodyweight exercise is the core move she thinks everyone should be doing

Woman on her back side on to the camera with legs bent in the air. she's on a high rise balcony with blocks of flats behind her.

The core is one of—if not the most—important area of your body to train. And it becomes even more crucial with age as muscle mass, balance and coordination naturally decline over time.

Building a strong core can keep you steady on your feet, reduce back pain and help you maintain good posture.