The reasons why patients have cramps at night are as follows: 1, calcium deficiency: the most common cause is calcium deficiency, calcium ions can inhibit the excitability of the neuromuscular junction, the excitability of the neuromuscular junction increases when calcium is deficient, children often show hand and foot twitching, increased excitability of the nervous system, often appearing to cry at night, adults will appear calf cramps, that is, at night there will be gastrocnemius muscle 2, local muscle injury: for example, through strenuous sports appear acute muscle strain, muscle in the injury will appear protective contraction and spasm, so there will be cramps, especially at night when the injury, muscle cramps will become particularly obvious.