A muscle strain is the stretching or tearing of muscle fibers. A muscle strain can be caused by sports, exercise, a sudden movement, or trying to lift something that is too heavy. Symptoms of a muscle strain include pain, tightness, swelling, tenderness, and the inability to move the muscle very well.
Update Date 5/9/2015
Updated by: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.