Subtitles section Play video Print subtitles Prolonged sitting in the flexed posture. Part one: biomechanical symptoms - lower body. Do you recognize this sitting position? Do you sit most hours of the day? Do you feel discomfort or pain in your upper or lower back? What happens to your body when you slump in your chair for too long? Prolonged sitting in this position will in time cause rigidity and tightness in the tight muscles, and we can see them colored in blue. And these are chronically short muscles, what we call locked short. In addition to the posterior leg muscles, the hip flexors are also chronically short from prolonged sitting. Rigidity in the hip flexor is a direct cause of weakness in the antagonist hip extenders. Muscle imbalance. Muscle imbalances are the number one cause of lower back pain. What happens to the sacroiliac joint? The joint between the sacrum and the pelvic bones. The sacroiliac joint and the sacroiliac ligaments are under load. What happens to the lumbar spine? Here, we can see a neutral spine and lumbar flexion. In prolonged slumped posture, the lumbar spine is flexed over time. Damage includes increase in posterior analyst strain, damage to the analyst of the disc, increase in intradiscal pressure. What happens to the connective tissues? Flexed postures place stress on the posterior passive tissues. In addition, the posterior ligaments are also impaired. In the second part of the video, we'll learn the biomechanical symptoms in the upper body.