Chronic left-sided back pain may be associated with chronic muscle strain caused by prolonged holding in one position, physical labour or bending over at work. Many patients may experience pain on one side of the back due to the asymmetrical exertion of the back in certain positions at work. In addition to this, heart problems should be monitored. Atypical angina may present with chest tightness, chest pain radiating to the left scapular region and left back pain.