<![CDATA[Bowing movement (ruku') in Islamic prayer requires repeated spinal flexion, which may impose mechanical stress on the spinal structures, particularly in lumbar region. This risk is potentially aggravated in individuals with spinal disorders such as disc degeneration or Hernia Nucleus Pulposus (HNP). Although ruku' posture is a routine daily activity among Muslims, biomechanical investigations into stress distribution during this posture remain limited. This study used finite element model (FEM) to examine von Mises stress distribution in intervertebral disc (IVD) at L4/L5 and L5/S1 levels during flexion movements from 0° to 90°. The geometric model was generated from a CT scan of a 55-year-old male patient. The simulation was conducted under an axial load of 500 N, which was resolved in accordance with the flexion angle's direction. The spinal structure was designed to include the cortical bone, cancellous bone, annulus fibrosus (AF), nucleus pulposus (NP), and related ligaments. The results showed that an increase in the flexion angle led to a substantial accumulation of stress, specifically inside AF and NP. L5/S1 segment demonstrated the greatest stress levels, with distribution mostly focused in the anterior portion of the disc. The highest stress in L5/S1 AF escalated over five times at 90° flexion relative to the upright posture. This pattern indicates a possible posterior displacement of NP, which may theoretically increase the biomechanical risk factors associated with disc herniation over time. Repetitive and intense bowing movements (ruku') can exert significant mechanical stress on the lower lumbar spine, specifically at L5/S1 segment. These results underscore the significance of biomechanical comprehension in religious activities and provide a foundational numerical framework to inform future musculoskeletal investigations regarding postural safety.]]>
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