Weakness in the thighs is mainly due to three reasons. 1, due to excessive muscle exertion in the thigh area, such as strenuous exercise, long distance travel, local consumption of a lot of electrolytes, energy and nutrition, there will be a decline in energy supply and weakness, and due to strenuous exercise and more lactic acid, lactic acid accumulation, will also lead to local acidity and tenderness, manifested as weakness. 2, due to in When resting, the muscles are not fully relaxed, the muscles are in a tense state, which will consume a lot of nutrition and energy, and because there is often a cold situation at night, it will cause the muscles to be more tense, the arterial blood supply decreases, the nutrient energy decreases, so it will aggravate the feeling of weakness. In addition, the venous return will also be contracted because of the cold, resulting in a decrease in return flow, resulting in the accumulation of metabolic products, aggravating the feeling of weakness. 3, because the nerve roots of the lumbar region are compressed, such as lumbar disc protrusion, especially the lumbar 1, lumbar 2, lumbar 3 parts of the disc protrusion compression nerve roots, will lead to a feeling of weakness on the front side of the thigh.