++
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.
++
++
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,
for ...