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.
Click for more of my blog posts on low back pain.
Steve Parker, M.D.
Paleo Diabetic 
I completely disagree with the “credentialed experts.” Credentialed experts can also disagree. From firsthand experience, I know that bad posture causes trigger points in numerous areas — esp. my back and neck — which thankfully I can fix myself at home using various natural means. I’ve also injured my back when attempting lift something heavy with bad posture. When I get sloppy with posture when working out, again, I pay for it with injury. Anyway, I highly recommend Claire Davies book Trigger Point Therapy Workbook. It has saved me literally thousands of dollars over the years. I never take pain meds — as I have also had great success with supplements to decrease acute inflammation. I also like the Sarno approach regarding the power of the mind to aid or impede pain/healing. Anger and negativity make the body muscles tighten up — not good for many things. I also highly recommend acupuncture — 2 sessions allowed me to avoid an allegedly “necessary” elbow surgery. I am not against meds per se, but if alternatives work for some people, their experience must be honored. Many roads lead to Rome — each person has to find what works for them.
Thanks for your input, A.
I’m familiar with Sarno’s book, I think called “Healing Back Pain.” It’s not just about backs.