The Navy SEAL Physical Fitness Guide 7
Muscle Structure and Function
The three major types of muscle are:" Cardiac muscle
" Skeletal muscle
" Smooth muscle
This discussion will be limited to skeletal muscles which, by converting chemical
energy to mechanical energy, produce movement. We will present a description of the
subtypes of skeletal muscles, including their characteristics and distribution. Although
there may be many new subtypes of skeletal muscle fibers, generally skeletal muscle can
be characterized into three basic types:
" Slow Twitch Oxidative (Type I)
" Fast Twitch Oxidative-Glycolytic (Type IIa)
" Fast Twitch Glycolytic (Type IIb)