I found a copy of this 1794 book, A Treatise on Muscular Action. This was a pioneering work on exercise. Apparently the author, John Pugh, invented apparatus for strengthening the muscles. The book doesn't illustrate the apparatus but it is mentioned in the testimonials at the beginning of the book.
What it does illustrate in elaborate detail, with engravings by Thomas Kirk, is the structure of muscles under tension and the grouping of muscles working with and against each other.
It is these engravings that are interesting to artists both interested in figure drawing and in action comics or animation.
The illustrations compare favorably to the work of such artists as Burne Hogarth, who has an equally strong line and way of illustrating groups of muscles in action.
Text at Amazon.com: A treatise on the science of muscular action. By John Pugh, anatomist.
Used copies of A Treatise on the Science of Muscular Action at Amazon.com.
Dynamic Figure Drawing
Dynamic Anatomy: Revised and Expanded Edition