There are two main reasons for sleeping with sore and weak legs at night: First, because the leg muscles are more active during the day, resulting in more local consumption of energy, electrolytes and nutrients, which leads to a decrease in local energy supply, resulting in a feeling of soreness and weakness. Second, because the muscle tissues are not fully relaxed during the night sleep, or there is a significant cold at night, do not pay attention to the warmth, will lead to muscle tissues continue to be in a state of tension, and because of the cold will lead to slow blood circulation, arterial blood supply will decline, therefore, the leg muscle tissues do not get sufficient electrolytes and energy supply, there will be soreness, weakness, weakness. Therefore, try to keep your muscles relaxed during nighttime sleep by putting a soft pillow on the back of your knee, keeping your hips and knees flexed, and be sure to keep your legs warm and not get cold during nighttime sleep.