No, according to these three credentialed experts at The Conversation. A snippet:
There is a common belief that “good” posture is important to protect the spine from damage, as well as prevent and treat back pain. Good posture is commonly defined as sitting “upright”, standing “tall and aligned”, and lifting with a squat technique and “straight back”.
Conversely, “slump” sitting, “slouch” standing and lifting with a “round back” or stooped posture are frequently warned against. This view is widely held by people with and without back pain, as well as clinicians in both occupational health and primary care settings
Surprisingly, there is a lack of evidence for a strong relationship between “good” posture and back pain. Perceptions of “good” posture originate from a combination of social desirability and unfounded presumptions.
Steve Parker, M.D.