The following diseases are common: First, lumbar spinal stenosis, the narrowing of the spinal canal, the nerve root canal and the intervertebral foramina, which squeezes the spinal nerves and leads to spinal nerve conduction dysfunction, with the clinical manifestations of weakness of the lower extremities, intermittent claudication, sinking of the lower extremities, muscle atrophy and heaviness, and incomplete paralysis of the lower extremities and dysfunction of the bowels in severe cases, lumbar spine CT and lumbar spine MRI can assist in the diagnosis. Secondly, thoracic spinal cord tumor occupation, thoracic spinal cord intramedullary and extramedullary tumor occupation, all of them can occur vertebral bundle compression, causing double lower limb heaviness, weakness, walking difficulty and other clinical symptoms, thoracic spine nuclear magnetic resonance can assist in the diagnosis, and can be localized and measured. In summary, the heaviness of both lower limbs is caused by the spinal cord cone bundle compression.