Add muscles

[moorepants]

Gerritsen, K. G. M., Bogert, A. J. van den, Hulliger, M., & Zernicke, R. F. (1998). Intrinsic Muscle Properties Facilitate Locomotor Control—A Computer Simulation Study. Motor Control, 2(3), 206–220. https://doi.org/10.1123/mcj.2.3.206
has this table:

which should be enough info to set up some muscle groups.