Principles of actuation in the muscular system of fish

Over the last 20 years, there have been tremendous intellectual and technological advancements in the fields of muscle biophysics, biomechanics, and musculoskeletal modeling. These advances have fueled a revolution in integrative muscle physiology. Whereas 20 years ago the notion of understanding the function and design of a muscular system from the molecular to the whole animal level was a dream, it is now becoming a reality. Fish represent an exceptional model for understanding the function and design of the muscular system of vertebrates. There are two fundamental reasons for this preeminence. First, the unique anatomical separation of the different muscle fiber types has made fish the most tractable model (i.e., the use and properties of the different muscle fiber types can be most easily studied). Second, fish utilize the broadest range of movement than any vertebrate. This diversity of movement imposes a wide array of challenges on the muscular system of fish and at the same time enables physiologists/biomechanists to observe how these challenges have been met. These features have permitted us to extract a number of general principles of actuation and control that have evolved over millions of years. Rather than summarizing the considerable literature on fish muscle function and fish swimming, this paper will focus narrowly on a relatively few studies that permit us to extract principles of actuation. These principles may in turn provide some insights into the design and construction of autonomous underwater vehicles (AUVs).