“Understand that the superficial muscles — the six pack or rectus abdominus muscles and the obliques — are designed to flex the spine forward, like in an ab curl or a side-bend. And when they activate, they shorten and pull away from the centre of your body. There’s a tissue down the centre of your belly, the linea alba, and all the ab muscles connect to that line. As your belly grows, that linea alba stretches to make room. The six pack will start to divide and move away from the centre. If you activate those muscles, they’re going to create an even bigger separation. Even when you get up off the couch or out of bed, that’s using your six pack: They shorten and pull away from the centre, tugging on that already-stretched, delicate tissue. Postpartum, almost every woman will have some degree of diastasis recti [ab separation], but the bigger it is, the slower and harder the recovery is.