The timing of the onset of low back pain varies from one type of low back pain to another, mainly because of the different causes of the pain. If sciatica occurs in young and middle-aged people, the most likely cause is a herniated disc in the lumbar spine compressing the nerve roots. The intervertebral disc is located between each vertebra, and when the body is upright at work during the day, the weight of the body can flatten and protrude the disc, and if it protrudes to the back side, it will squeeze the nerve roots immediately adjacent to it, causing lumbago combined with soreness, numbness and pain on the back and outside of the lower limbs. The lumbar region is located in the lower part of the torso and bears the most weight, plus the lumbar region is the most active part of the torso, and as the work day progresses, the more the lumbar discs protrude, so the more the lumbar pain increases. After a night’s rest, the intervertebral discs will be slightly reset, the pressure on the compressed nerves will be reduced, and the low back pain will be relieved, so this type of patient often has less back pain in the morning, or even no pain at all, but after working until noon, that is, the onset of low back pain, and the more pain in the evening. Another type of low back pain has the opposite time, waking up in the morning with the most pain, and after activity, the pain symptoms are reduced. This is because tissue inflammation will accelerate the metabolism of local tissues. After sleeping all night without activity, the waste materials produced by metabolism accumulate in local tissues, stimulating the painful nerves and causing back pain, after getting up and moving, blood circulation increases, taking away some of these waste materials, and the pain will be reduced. There is another kind of back pain that often occurs in the dead of night, which is cancer pain, and this pain can often wake a person from sleep. One characteristic of this cancer pain is that tapping on the painful area will usually intensify the pain, which is the opposite of the general muscle pain that is more comfortable when tapped.