Chapter 2

At the conclusion of this chapter, the student should be able to:

• 1. Classify joints according to structure and explain the relationship between a joint structure and its capacity for movement.
• 2. Explain how the schedule of ossification of epiphyseal cartilage is related to the nature of activities suitable for different age groups.
• 3. Name the factors that contribute to joint range of motion and stability and explain the relationship that exists between range of motion and stability.
• 4. Assess a joint’s range of motion, evaluate the range, and describe desirable procedures for changing it when indicated.
• 5. Name and define the orientation positions and planes of the body and the axes of motion.
• 6. Demonstrate and name fundamental movement patterns using correct movement terminology.
• 7. Isolate and name single joint actions that are part of complex movements.
• 8. Perform an anatomical analysis of the joint actions and planes of motion for a selected motor skill.

It is customary—especially for students of human movement and exercise—to begin the study of anatomy with a detailed study of the bones, then to proceed to the joints, and then to the muscles. This path of investigation sometimes dampens the enthusiasm of students, whose chief focus of interest is movement. Therefore, this chapter and the next emphasize the concept of the total musculoskeletal system as a mechanism for motion. It is hoped that by using this concept the student will find the study of the structural elements of this system more meaningful.

As the phrase implies, the musculoskeletal framework is an arrangement of bones and muscles. Adjacent bones are attached to one another by joints, which provide for the motion of the articulating bones, and the muscles that span the joints provide the force for moving the bones to which they are attached. Mechanically, the total bone–joint–muscle structure is an intricate combination of levers that makes possible a great number of coordinated movements, ranging from the small hand and finger motions used in assembling a television set or playing the piano to the total body movements of a swimmer or a pole vaulter. Any single one of the levers involved in such movements is relatively simple.

In physics we are taught that a lever is defined as a rigid bar that turns about a fulcrum (fixed axis or pivot) when force is applied to it at some specific point. An anatomical lever, therefore, is simply a bone that engages in an angular or turning type of movement when a force is applied to it. This force may be the contracting force of a muscle attached to the bone, or it may be an external force such as gravity or an external weight. If the force is muscle, it is always a pulling force, because muscles, being flexible, are unable to push; they can only pull. If the force is external, such as when a weight is too heavy to ...

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