Stretching back with cramps may exist muscle spasm, poor blood circulation in the muscles or the existence of lumbar diseases. 1. Muscle spasm: stretching will cause most of the muscle contraction, due to a long period of inactivity will lead to muscle weakness, activity will occur after the muscle spasm, thus causing the symptoms of cramps. 2. Poor blood circulation: poor blood circulation in the back muscles due to various reasons, coupled with the contraction of the muscles caused by stretching, may result in transient ischemia, causing the symptoms of cramps. 3. Lumbar diseases: If there are diseases such as lumbar disc herniation or lumbar muscle strain, it will induce or aggravate the symptoms after stretching, and cramp is one of the clinical manifestations. It is recommended that patients should go to the hospital for examination to identify the cause and targeted treatment, at the same time, should change habits, daily life need to exercise, strengthen muscle strength.