When exercising, it is easy to have muscle cramps in the lower limbs, commonly for calf muscle cramps, the specific reasons are as follows: 1, muscle fatigue, when excessive exercise, especially when prolonged strenuous exercise, due to more than muscle exercise load, prolonged in anaerobic metabolism muscle ischemia, hypoxia will cause leg cramps. At the time that there is severe pain and inability to move, need to immediately deal with such as massage, etc. 2, muscle injury, when the exercise, especially when the intense exercise, muscle contraction is easy to cause strains. This can lead to cramps and pain, inability to move, severe local tearing pain and swelling, pressure pain. 3, lumbar spine disease compression nerve caused by the lumbar spine disc protrusion, due to increased load on the lumbar spine during exercise, easily lead to increased pressure on the lumbar spine to stimulate the nerves, resulting in muscle cramps in the lower limbs, need MRI examination to confirm the diagnosis.