The spine is a highly complex structure, consisting of multiple
intervertebral joints capable of multi-degree of freedom movement.
Due to this complexity, its control is regulated by a vast array of
seemingly uniquely designed muscles. How these muscles generate
force determines spine movement, loading, and stability; thus, it is
important to understand how all the muscles function and interact as
a complete system. The use of electromyography has been critical in
determining how the spine muscles are activated and load the spine
under a variety of conditions (e.g. Marras and Granata, 1997; Larivière
et al., 2003; Kavcic et al., 2004; Dufour et al., 2013). However,
knowledge of the fundamental structural design of these muscles, a
powerful determiner of function, is lacking and requires further study.