The two most current trainings I’ve taken for pilates and barre have emphasized “elongated neutral spine,” as opposed to tucking or flattening. This is also consistent with one of my favorite yoga presenter’s (Sadie Nardini) anatomy training, which I’ve taken both online and studied with her in person.
I agree that flat back is old school and neutral spine is the way to go.
People have altered their spine to being straight, losing the natural lumbar curve because of always pressing the low back into the floor. It takes a long time to get the spine back to the natural, neutral curvature.
Normal back cues may not always be good if normal is a tilted pelvis.
When teaching anyone mat exercises neutral spine is biomechanically correct. As others have indicated, if a client has tight hip flexors, they will automatically be anteriorly tilted or conversely if they have tight hamstrings &/or tight hamstrings with spinal extensors(as seen in stenotic patients), they will present with a posterior tilt.
Neutral spine is referring to the pelvis on the lumbosacral junction. An area that is commonly injured, weak, possesses muscle imbalances and should be addressed first with ANY TYPE of client for optimal results…