Running leg numbness may be caused by the following reasons, 1. There may be vascular lesions in the lower limbs, such as when the large arteries in the lower limbs are embolized or occluded, it may cause poor blood circulation in the lower limbs. In the early stage of such diseases, patients may not feel any clinical symptoms, but once the strenuous activities such as running, it will lead to increased ischemia of the lower limbs, followed by a series of symptoms such as coldness, purple and numbness in the lower limbs. Some patients will have obvious limp, that is, after running for a period of time because of the above-mentioned symptoms of the lower limbs can not be active. 2, this situation may be caused by peripheral nerve lesions, such as in patients with lumbar disc herniation, or sciatica, itself in the lower limbs may have mild symptoms, but once the intense activity of running, it is possible to make the condition worse, followed by numbness in the lower limbs. 3, may also be caused by the peripheral nerve compression, such as the nerve in the lower limbs due to muscle spasm caused by the compression, this running may make muscle spasm aggravated, and then lead to nerve compression aggravated, will appear the symptoms of lower limb numbness.