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