A muscle strain is an injury that damages the internal structure of the muscle. It may be small or severe enough to cause internal bleeding and lengthening of muscle fibers. If the damaged parts of the muscle pull away from each other, it is called a muscle rupture.

Muscles of the Back
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A muscle strain is caused by tension or stress applied to the muscle that it cannot withstand. There are several ways that this can happen:

  • Muscle may not be ready for sudden stress
  • Tension may be too much for the muscle to bear, such as lifting a weight that is too heavy for you
  • Muscle is used too much on a certain day

Certain areas have muscles that are more likely to be strained than others, including:

Muscles that cross two joints are at the greatest risk.