Hello Thank you for trusting HealthcareMagic Dear possible causes for pain while lifting weights are 1. Rotator cuff tears; This is a common cause of pain in the upper arm caused by damage to one of the tendons of the rotator cuff - a group of muscles that surround the shoulder joint and control the movement and stability of the shoulder. 2.Shoulder impingement:This is a collective term for anything that reduces the amount of space in part of the shoulder, known as the subacromial space, which places pressure and friction on the rotator cuff. It is a common cause of shoulder and upper arm pain affecting approximately 20% of people at some point usually caused by repetitive overhead activities such as throwing or swimming, aging, posture or genetics. 3.Frozen shoulder:Thickening and tightening of the joint capsule, a fluid filled sac that surrounds the glenohumeral (shoulder) joint.Treatment: Rest from aggravating activities, ice, rotator cuff exercises to strengthen and stretch the muscles and steroid injections. If the impingement is caused by small bone spurs in the subacromial space, surgery will be required to remove them, known as a subacromial decompression. If symptoms not improved please consult your doctor he will examine and treat you accordingly. Take care. Regards Dr. Penchila Prasad Kandikattu Internal Medicine Specialist