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02-11-2009 11:24 AM |
muscles of breathing we discussed the accessory muscles of the upper chest—the rhomboids and the pectoralis minor. This Scientific Key looks at the accessory muscles of the lower chest and abdomen, specifically the rectus abdominus, quadratus lumborum and the psoas. Let’s look at each of these muscles in turn.
The psoas and quadratus lumborum are inter-related muscles in that contraction of one evokes contraction of the other through neurophysiological connections. This works well because both muscles wrap around and stabilize the lumbar spine (see right).
© 2007 Raymond A. Long MD.
© 2007 Raymond A. Long MD.
The quadratus lumborum originates on the medial iliac crest and inserts on the lower border of rib 12 (and the lumbar vertabrae). Contracting this muscle acts to arch the lumbar spine and draw the floating ribs down (see left).
The psoas does not actually attach to the ribcage and so is not truly one of the accessory muscles of breathing. Contracting the psoas does, however, signal the quadratus lumborum to contract. The psoas also helps stabilize the lumbar spine during seated breathing exercises. To learn more about this important muscle please click here for “Awakening the Psoas.”
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