"The muscular system gives humans their shape and helps them move their body. Without muscles, people would look very different--and they wouldn't be able to move! This inside guide to our muscles uses . . . examples, discussion questions, sidebars, and fact boxes to dive in to what makes the muscular system work. Age-appropriate language is used in conjunction with detailed photographs and diagrams to explain key concepts such as main muscles in the body, ways muscles can be strengthened or weakened, and the primary functions of the muscular system, including maintaining posture, strength, and movement"--Provided by publisher.