Never do thoracic extension exercises
Thanks!
Thoracic extension=flat back posture.
Also, avoid a fixed spine during movement. Fixed spine=spinal cord injuries.
I mean, please do avoid a flexed low back. But the thoracic spine should never, ever be forced into extension. The solution to thoracic flexion is always more thoracic flexion. The natural curve of the lumbar and thoracic spine is an s curve -flexion on one and extension on the other -a posture that can take hammer blows to the ribcage. The natural curve of the cervical spine is, of course, extension.