Which muscle is primarily involved when moving from a supine position to sitting?

Which muscle is primarily involved when moving from a supine position to sitting?

• A. Rectus abdominis
• B. External oblique
• C. Transverse abdominis
• D. Iliopsoas

Answer: (A)

Moving from lying flat to sitting up mainly requires bending the spine to bring the chest toward the pelvis. The rectus abdominis is the primary muscle that produces this trunk flexion, pulling the ribcage toward the pelvis and curling the spine forward to lift you into a seated position. The external oblique can assist with flexion and also helps with side bending and rotation, but it isn’t the main driver. The transverse abdominis provides core stability rather than producing the big bend of the trunk. The iliopsoas mainly flexes the hip, so it helps more when the legs are involved in lifting the torso, but for pure moving from supine to sitting, the spine-flexing action of the rectus abdominis is the key.

Moving from lying flat to sitting up mainly requires bending the spine to bring the chest toward the pelvis. The rectus abdominis is the primary muscle that produces this trunk flexion, pulling the ribcage toward the pelvis and curling the spine forward to lift you into a seated position. The external oblique can assist with flexion and also helps with side bending and rotation, but it isn’t the main driver. The transverse abdominis provides core stability rather than producing the big bend of the trunk. The iliopsoas mainly flexes the hip, so it helps more when the legs are involved in lifting the torso, but for pure moving from supine to sitting, the spine-flexing action of the rectus abdominis is the key.