shoulder and upper back muscles causes these muscles to tear (on a microscopic level). Your body tries to prevent this tearing by forcing these muscles to knot up. This results in muscle spasms.

Middle back ... to pain in the middle of your back. In addition to both sharp and dull pain, strains and sprains may cause swelling, difficulty moving, bruising, and muscle spasms.

Medically reviewed by Andrea Chisholm, MD FACOG Are you experiencing back pain during pregnancy? If so, you're not alone. While most pregnant people feel the aching in their lower back, some report ...