The most common cause of acute back or neck pain is a muscle injury, in which muscle fibers stretch too far and tear. Muscle injury may be caused by overuse, such as from heavy lifting, as well as by repetitive motions that put continual stress on the back or neck muscles.
While a muscle injury may not sound like a serious issue, the resulting pain can be severe. Most muscle injuries alleviate within 6 weeks using treatments such as over-the-counter pain medicines, heat or ice therapy, or stretching exercises.