Organization, flow, and structure are good and consistent. The objectives at the beginning of each chapter and the terms/chapter quiz at the end are beneficial.
The text is not culturally insensitive or offensive in any way. It is unbiased and inclusive of all races, ethnicities, and backgrounds.
This is a pretty comprehensive text for introductory fitness & wellness concepts. The only mechanism discussed is recruitment of more motor units, when there are at least a few different ways that nerves can generate more force.
Accuracy can be difficult at times to determine, as there are several claims being made that are not accompanied by in-text citation. There is also one chapter that does not list references, but rather notes (that I assume the author wrote) that indicated they needed to find references and update the format.
The content is highly relevant and seems up-to-date. One very minor suggestion would be to mention type IIb muscle fibers are often times referred to as type IIx. Students will see that a lot if they read the literature, so it would be helpful for them to have seen it in text beforehand.
Overall, basic terminology and concepts are explained very clearly for introductory learners. One suggestion for improvement would be to have more diagrams/pictures, specifically when discussing anatomy (e.g. anatomy of motor units).