Bending the knees to close the abdomen will back pain may be caused by the movement posture is not standard, lumbar muscle injury, lumbar spine disease and other reasons. 1. Exercise posture is not standard: do not have a standard posture when bending knees and abdominal movements, long-term non-exercise, exercise is too strenuous and other reasons, may lead to the emergence of back pain. Pay attention to the standard posture, moderate exercise, and avoid excessive exercise. 2. Lumbar muscle injury: Doing knee bending and abdominal exercise causes lumbar muscle injury, or lumbar muscle injury, which may cause pain in the lower back. 3. Lumbar spine disease: patients with lumbar spine disease such as lumbar disc herniation and lumbar spine slippage may suffer from lumbar spine disease, and they may also suffer from lumbar pain when they do the exercise of bending knees and tightening abdominal muscles, because the curvature is too large, which leads to excessive force on the lower back area. Bending the knees to close the abdomen lumbar pain can be appropriate local hot massage to relieve, if you can not relieve should be timely consultation, under the guidance of the doctor’s clear diagnosis and treatment. Daily attention should be paid to lumbar warmth, more rest, avoid improper exercise on the waist muscle loss.