Chapter 21

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

• 1. Explain how each of the following influences the action of swinging bodies: weight of the body, length of the pendulum, angular momentum, potential-kinetic energy, centripetal–centrifugal force, and friction.
• 2. Describe how to initiate pendular action, increase the height of a swing, alter the period, change grips, and dismount safely.
• 3. Explain how each of the following influences the flight path of unsupported bodies: angle of projection, vertical velocity, gravity, and angular momentum.
• 4. Describe how to initiate and control rotation of unsupported bodies.
• 5. Analyze the performance of a suspension and a nonsupport movement, following the outline for kinesiological analysis described in Chapter 1.

Climbing, hanging, swinging, and other suspension activities were more commonly engaged in by our early ancestors than by members of more recent generations. The modern version of these brachial activities is seen in the trapeze activities of the aerial artist at the circus, in gymnastics events on the high bar, parallel bars, uneven bars, and rings, and in various forms of hanging on ladders and ropes in the gymnasium and on the playground. Success in suspension activities depends on considerable strength and endurance, particularly of the hand, arm, and shoulder musculature, and the ability to adjust body positions to counteract or take advantage of the forces acting on the body (Figure 21.1). Ladder, rope or rock climbing, and brachial locomotion are modifications of locomotion. Where swinging movements of a suspended body are involved, the principles of a pendulum, angular momentum, and centripetal–centrifugal forces are major considerations.

###### Figure 21.1

Movement of the body in suspension. This maneuver on the still rings illustrates the need for good muscular development in the arms and shoulders. Courtesy of Springfield College.

### Principles Related to Hanging and Hand-Traveling Activities

• 1. In hanging activities the muscles of the arm and shoulder girdle must contract to protect the joints. The pull of the body’s weight puts stress on the joints by tending to separatethem.
• 2. Hand traveling is a locomotor pattern governed by the principle of action and reaction. As in walking, force applied against a supporting surface in one direction causes the body to move in the opposite direction. Hand traveling sideward on a bar or rail without swinging is achieved by alternately moving one hand away from the other hand, and then moving the second hand toward the first. As the first hand moves, the second hand pushes laterally against the apparatus. Both hands share the weight equally for a moment, then the second hand is released and brought toward the first hand while the first hand is pulling laterally on the apparatus.
• 3. The action used in hand-climbing activities is essentially a pull-up action. In rope climbing, ...

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