One leg usually can’t make the effort is the feeling of weakness, this situation has two reasons can lead to: 1, may be caused by cerebrovascular accidents, common is cerebral infarction or cerebral hemorrhage, usually in addition to a foot of muscle strength decline, will also be accompanied by the same side of the upper limbs of the decline in muscle strength, accompanied by numbness, fatigue and other sensations, the serious will also have dizziness, facial paralysis, or even coma, etc. 2, may be caused by lumbar spine disease compression of the nerve roots of the lower limbs. Lumbar spine disease compression of the nerve roots of the lower limbs and caused by common lumbar disc herniation, lumbar spinal stenosis or lumbar spine slipped, compression of the nerve roots of the lower limbs on one side of the symptoms of fatigue, numbness, but usually accompanied by the symptoms of the lower limb nerve pulling pain.