Chapter 17

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

• 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.

### Joint Action Patterns

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 Application

#### Momentary Contact

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 ...

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