Silvia is looking for a more complex core exercise. She wants to work her coordination and balance as she also works her abs and her back muscles. Which exercise BEST fits her needs?

a bridge
crunches
the bird dog
lunges

The bird dog exercise BEST fits Silvia's needs. The bird dog exercise is a challenging core exercise that requires coordination and balance. It targets the abs and back muscles while also involving the muscles in the hips and shoulders.