When you find sore feet while sleeping, it may be caused by muscle strain, calcium deficiency, etc. The details are as follows: 1, muscle strain: for example, a lot of sports during the day, which will cause a large amount of lactic acid accumulation in the calf area, and in a quieter state at night, you will feel the obvious soreness and pain in the calf, and sometimes muscle spasm; 2, calcium deficiency: calcium ions can inhibit the excitability of muscle joints, when calcium deficiency neuromuscular excitability will increase, which will cause spasmodic pain in the calf, especially at night, which will cause cramps in the calf and leg soreness, leg swelling, etc.