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At the conclusion of this chapter, the student should be able
to:
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- 1. Name the common problems associated with the diverse
forms of receiving impact.
- 2. Explain how the work–energy, impulse–momentum,
and pressure-area relationships apply to receiving the impact either
of one’s own body or of external objects.
- 3. State the principles related to avoiding injury while receiving
impact and furnish an application for each.
- 4. State the principles related to maintaining and regaining
equilibrium while receiving impact and furnish an application for
each.
- 5. State the principles related to accuracy and control while
receiving impact and furnish an application for each.
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The word impact is derived from
the Latin word impingere, “to
press together.” Impact is further defined as force of
contact, violent collision, striking together. Receiving impact
is opposing or resisting in some manner the force with which a moving
body tends to maintain its speed and direction. Impact may be from
one’s own body, as in landing from a jump or fall, or imparted
by external objects, as in catching or spotting.
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Impact of one’s own body is experienced following any
fall through space. Such falling motion, which occurs subsequent
to a jump, a dive, or an accidental fall, has a rapidly increasing
velocity because of the uniform acceleration effect of gravitational
force. When the body lands on a supporting surface, impact has been
said to occur. The impact is felt as the force of contact. Likewise, impact
is experienced in a horizontally moving body when the motion is
stopped as a result of contact with a resisting surface, such as
a wall or another obstacle.
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Examples of receiving impact from external objects are commonly
seen in sports. Baseballs are caught or fielded with the hands,
hockey balls and pucks are received with a stick, soccer balls are trapped
with the feet, and blows from an opponent’s fist are received
by various parts of the body. Examples of receiving impact are also
seen in industry and in daily life. Cartons and tools are tossed
from one person to another, red-hot rivets are caught in tongs,
and victims from a fire are caught in nets or air bags.
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Impact generally has a negative connotation, but there are benefits
to controlled impacts, such as mechanical loading of bone during
walking. Specifically, it is widely accepted that bone will adapt
to the mechanical stresses placed upon it. Intuitively, it is apparent
that the bones of adults and adolescents will not adapt in the same
manner, yet the bones of both groups are altered by mechanical loading
(Ruff et al. 2006).
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Problems and
Concepts
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What are the particular problems involved in these diverse forms
of receiving impact, and what are the principles that enable us
to solve these problems satisfactorily? In the reception of the body’s
own impact, the chief ...