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(A) The relationship between muscle stretch ratios in selected LAM, PC, IC and PR muscle bands and (B) foetal head descent in the birth canal. The shaded region denotes the values of stretch tolerated by non-pregnant appendicular striated muscle without injury. (C) Initial and final muscle length. (D) Maximum corresponding stretch ratio of each LAM muscle corresponding to foetal head descent. Reproduced with permission of [26]. Copyright NIH Public Access, 2005.
