The Collaborative International Dictionary of English v.0.48:

Musculature \Mus"cu*la*ture\, n. [Cf. F. musculature.] (Anat.)
   The muscular system of an animal, or of any of its parts;
   musculation.
   [1913 Webster]

WordNet (r) 3.0 (2006):

musculature
    n 1: the muscular system of an organism [syn: muscular
         structure, musculature, muscle system]

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "musculature":
   beef, beefiness, brawn, brawniness, elasticity, heftiness,
   huskiness, involuntary muscle, muscle, muscularity, physique,
   sinew, sinewiness, sinews, thew, thewiness, thews, tone,
   voluntary muscle