At the conclusion of this chapter, the student should be able
- 1. Classify activities involving push or pull patterns
according to the nature of the force application.
- 2. Name and discuss anatomical and mechanical factors and
principles that apply to representative push or pull activities.
- 3. Analyze the performance of someone performing a push-pull
skill under each of these force application conditions: momentary
contact, projection, or continuous application. Follow the kinesiological
analysis outline presented in Chapter 1.
A person pushes a table across the room, a boxer jabs at an opponent,
a traveler lifts a suitcase onto an overhead rack, an archer shoots
an arrow from a bow, and a schoolteacher lifts open a window. As
widely diverse as these activities seem, they all have a common
denominator: Each involves moving an external object, either directly
by some part of the body or by means of an implement, in a pushing
or pulling pattern.
In pushing and pulling patterns of motion, the basic joint actions
are flexion and extension in one or more of the extremities. The
joint actions in the upper extremities are characterized by flexion and
extension in the elbow while the opposite movement is occurring
in the shoulder. In the lower extremities, extension occurs simultaneously
in the hip, knee, and ankle. This simultaneous and opposite joint
action is a primary characteristic of push-pull patterns. All joint
motions occur at the same time or very near the same time.
The simultaneous nature of the joint motions in push and pull
patterns produces a rectilinear path of motion at the distal end
point of the segments involved, as opposed to a curvilinear path.
Such a rectilinear path means that all forces produced by segmental
motion are applied directly to the object and that this force is
applied in the direction of motion. Keeping this in mind makes it apparent
that the primarily simultaneous push-pull patterns are of greatest
value when it is important to apply a large force (overcome a large
resistance) or to apply a force with maximum accuracy. All the forces
involved are applied directly in line with the object being moved.
There are no large-magnitude tangential forces.
A push, pull, or lift may be applied either directly or indirectly
to an object. In the latter instance, the push or pull pattern is
used to develop potential energy in an elastic device such as a
bow or slingshot. When the elastic structure is released, it imparts
force to the movable object, causing the arrow or shot to be projected
into the air.
Nature of Force
Movements such as striking and hitting are characterized by momentary
contact made with an object by a moving part of the body or by a
held implement. The object itself ...