As you swing your arms down and forward with force, your back body has to decelerate the mass and momentum of the arm swing. The back works along with the posterior chain just like it does in life activities. This exercise is safe for diastasis and pelvic floor issues only if you are able to manage pressure. If you are unsure if you are managing pressure pay attention to if you feel any outward bulging or downward pressure as you swing the arms forward. Make sure that you forcefully exhale as your arms travel down in front of you.