A strain is a stretching
injury to a muscle or a musculotendinous unit caused by mechanical overloading. This type of
injury may result from an unusual muscle contraction or an excessive forcible stretch. Although there usually is no external evidence of a specific
injury, pain, stiffness, and swelling exist. The most common sites for muscle strains are the lower back and the cervical region of the spine. The elbow and the shoulder are also supported by musculotendinous units that are subject to strains. Foot strain is associated with the weight-bearing
stresses of the feet; it may be caused by inadequate muscular and ligamentous support, over weight, or excessive exercise such as standing, walking, or running.