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40 Cards in this Set

  • Front
  • Back
The application of mechanical laws to living structures, specifically to the locomotor system of the human body.
The constant, external force of attraction between the center of the earth and objects near it.
Center of Gravity
The point of the body about which all the parts exactly balance each other. The whole weight of the object may be assumed to act at this point.
Line of Gravity
Line of force from the center of gravity to the center of the earth.
Base of Support
The area of and between the points of contact with the floor. Major factor in the stability of an object. The larger the base of support, the more stable the object - may be at the cost of mobility.
Any rigid bar that turns about a fulcrum when a force is applied to it and overcomes a resistance force as it turns.
A simple machine composed of a small wheel, sometimes turning in a block, with a grooved rim in which a chain or rope runs to raise a weight attached at one end by pulling on the other end.
Anatomical location of the C.O.G.
Approximately just anterior to the upper 1/3 sacral vertebrae when the body is in the anatomical position.
What might effect the location of the C.O.G.?
The arrangement of body segments in space, weight distribution, addition or deletion of external mass, even breathing changes the location of the center of gravity.
Anatomical location of the L.O.G.
In anatomical position, drawn from umbilicus strait to the floor, equidistant between feet. From the side view, posterior to the axis of the hip, anterior to the axis of the knee, and approximately one inch anterior to lateral malleolus.
What are three factors that influence mechanical stability?
Size of the base of support, height of the object's center of gravity (the lower the C.O.G. the greater the stability), where the line of gravity falls in relation to the base of support (keeping the L.O.G. within the B.O.S. greatly enhances stability.
An action of one body on another producing either a push or pull.
What are the characteristics of ALL forces?
Magnitude of the action, line of application, sense, point of application.
What is magnitude in relevence to Force?
How much force is being applied.
What is Line of Application in relevence to Force?
Line along which force acts. A line through the C.O.G. will result in linear motion. A line above, below, or to the side of the C.O.G. will result in rotation.
What is Sense in relevence to Force?
Direction of the force application.
What is Point of Application in relevence to Force.
Exact point at which the force is applied to an object.
Linear Force System
All forces occur along the same line of application and in the same plane. (Tug of war or sitting to standing).
Parallel Force System
All forces occuring in the same plane but not along the same line of application. (teeter-totter)
What are the parts of a lever and their anatomical equivalents?
Lever arm, anatomically equivalent to bones (primarily long bones). Fulcrum, anatomically equivalent to joints. Effort, anatomically equivelent to muscles. Resistance, anatomically equivalent to body weight. Can be any external resistance however.
First Class Lever
The fulcrum is located between the resistance and the effort.
What is an example of a First Class Lever?
Cervical flex/ext and full elbow extension by triceps.
Second Class Lever
The resistance is located between the fulcrum and the effort.
What is an example of a Second Class Lever?
When rising on the ball of the foot.
Third Class Lever
The effort is located between the fulcrum and the resistance.
What is an example of a Third Class Lever?
Biceps action. Most lever systems within the body are third class levers.
Mechanical Advantage
A measure of the efficiency of a lever. (MA) is the ratio of the effort arm (EA) to the resistance arm (RA).
When is a lever considered efficient?
When it has an MA greater then one.
What is the efficiency of a First Class Lever?
Lever can be efficient or ineffient.
What is the efficiency of a Second Class Lever?
Lever is always efficient because the effort arm is longer then the resistance arm.
What is the efficiency of a Third Class Lever?
Lever is always inefficient because the effort arm is always shorter than the resistance arm. It enhances speed and range of motion.
What are hte externally applied forces to the human body?
Gravity, Friction, Buoyancy, and Manual and Mechanical forces
A force exists whenever an oject is made to slide on another line of application that is parallel to contact surface, friction force produced is in the opposite direction of movement = parallel force system. Friction may also be a component of internally applied forces.
Water resistance exerting a force upward. This force is equal to the weight of the volume displaced.
Manual and Mechanical Forces
Forces applied in physical therapy procedures. Manual muscle testing and assistive and resistive exercises.
What are the components of internally applied forces?
Muscles, ligaments and joint capsules, bones, and joints.
What is the relevence of Muscles in internally applied forces?
Exerting forces through contraction.
What is the relevence of Ligaments and Joint Capsules in internally applied forces?
Tension of fascia and ligaments guide or limit motion by acting as levers which make them stabilizing force.
What is the relevence of Bones in internally applied forces?
Major determinant of the efficiency with which the force is applied (levers).
What is the relevence of Joints in internally applied forces?
Act as fulcrums of motion.