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Ch 8 Biomechanics

Clinical Kinesiology Chapter 8

The study of forces and the motion produced as a result of those forces: mechanics
Using principles and methods of mechanics and applying them to the structure and function of the human body: biomechanics
In terms of biomechanics, ________ deals with factors associated with non-moving systems, while __________ involves factors associated with moving systems. statics / dynamics
Dynamics can be divided into ________ and _________. kinetics and kinematics
_________ deal with the forces that cause movement in a mechanical system, while __________ involves the time, space, and mass aspects of a moving system. kinetics / kinematics
The branch of kinematics that focuses on how bones move through space: osteokinematics
The branch of kinematics that deals with the manner in which joint surfaces move in relation to each other. arthrokinematics
ANY push or pull action or influence that moves or deforms and object: force
A quantity having both magnitude and direction: vector
A quantity that ONLY describes magnitude (ie. volume, length, area, mass): scalar quantity
The tendency of a force to cause rotation around an axis: torque
A vector that describes speed (measured in units like feet per second, or MPH): velocity
A change in velocity: acceleration
Name Newton's 3 Laws of Motion: 1) Law of Inertia 2) Law of acceleration 3)Law of Action/Reaction
The amount of matter a body contains mass
The property of matter that causes it to resist any change in its motion in either speed or direction: inertia
A force developed by two surfaces: friction
The law of motion that states that an object at rest tends to stay at rest and an object at motion tends to stay at motion: Newton's 1st Law of Motion: The Law of Inertia
The law of motion that states: The amount of acceleration and the ability to change direction depends on the strength of the force applied to the object. Acceleration is inversely proportional to the object's mass. Newton's 2nd Law of Motion: The Law of Acceleration
The law of motion that states: For every action, there is an equal and opposite reaction (The reaction is ALWAYS = in strength to the action, and occurs in the opposite direction) Newton's 3rd Law of Motion: The Law of Action/Reaction
What are the 2 types of forces that cause body motion? Internal forces and external forces
The type of force is caused by muscle contraction, ligament restraint, and bony suppport: internal forces
The type of force is caused by gravity, weights, friction, or even another person: external forces
PTs and PTAs must be able to use their knowledge of _______ and _______ forces when treating patients. internal / external
Knowing hoe internal and external forces work allows us to determine: How muscles are ________, how to _________ muscles, and how to help the patient perform specific _________. working / strengthen / activities
The force that results when 2 or more forces are acting along the SAME LINE (whether it be in the same or opposite directions): linear force ie) 2 people pulling a rope
Force that occurs in the SAME PLANE, in the same or opposite directions: parallel force ie) Jewett brace
2 or more forces that act from a common point (at the object), but pull/push in different (divergent) directions. This produces a resultant force: concurrent forces
The net effect of 2 divergent forces pushing or pulling the same point on an object: resultant force (it is somewhere in between the two concurrent forces) ie) anterior and posterior deltoids...have common insertion, but different origins.
When trying to find the resultant force of 2 concurrent forces, use the __________ method. parallelogram
Force is a ________. It has an ________ _______, a ________ ____ _______, and a __________. point of application, line of pull, magnitude
Type of force that occurs when joint surfaces are being pushed closer together: compression
Type of force that occurs when joint surfaces are pulled apart: traction (or distraction)
Force that occurs parallel to the surface of the joint: shear
Occurs when two or more forces act in equal but opposite directions to result in a turning effect: force couple ie)scapular rotation
The ability of force to produce rotation around an axis: torque (or 'moment of force')
The amount of torque a lever has depends on these 2 things: 1) the amount of force exerted 2) the perpendicular distance from the muscle's line of pull to the axis (moment arm or torque arm)
What is the equation for torque? Torque = Force x Moment Arm
The amount of torque a lever has depends on the ________ exerted, and the length of the ________ _______. force / lever arm
Torque is greatest when the angle of pull is at ____ degrees, and ________ as the angle of pull either decreases or increases. 90 / decreases
As a joint moves toward 0 degrees (ie. elbow extended), the moment arm decreases and nearly all the force generated by the muscle is directed at the joint, compressing it. This is __________ _________. stabilizing force
When most of the force generated by the muscle is directed at rotating the joint (happens when the distance between the line of pull and the joint are larger -- joint at or near 90 degrees) this is ________ _________. angular force
The presence of the patella increases the _________ ______ of the knee joint, allowing for better rotation. moment arm
True or False? As a muscle contracts through its range of motion (ROM), the amount of angular, stabilizing, and dislocating force remains constant. FALSE!!!!! As a muscle contracts through its range of motion (ROM), the amount of angular, stabilizing, and dislocating force CHANGES.
Moment arm and angular force is greatest at ____ degrees. 90
As the joint moves BEYOND 90 degrees toward 180 degrees (or more like 150 degrees in the case of elbow flexion), the moment arm decreases, producing a force directed away from the joint. This is a _________ ________. dislocating force
A joint becomes less efficient at moving or rotating when the joint angle is at the __________ or near the _______ of joint range. beginning / end
The presence of the __________ at the knee joint increases the moment arm of the quadriceps muscle by holding the tendon out and away from the femur, increasing the ________ ________. patella / angular force
When an object is balanced and all torques acting on it are even, it is said to be in a state of _____________. equilibrium
How secure or unstable the state of equilibrium is depends primarily on the relationship between the object's __________ ____ __________ and ___________ ____ ____________. center of gravity (COG) / base of support (BOS)
The mutual attraction between the earth and an object: gravity
_________ ________ is always directed vertically downward, toward the center of the earth; for our purposes, the ground. Gravitational force
The balance point of an object at which weight on all sides is equal: center of gravity (COG)
The planes of the body intersect at the: center of gravity (COG)
In the human body, the COG is located in the midline, slightly anterior to: the second sacral vertebra (S2)
The imaginary vertical line passing through the COG, toward the center of the earth: line of gravity (LOG)
The part of the body that is in contact with the supporting surface: base of support (BOS)
What are the 3 types of equilibrium? stable, unstable, neutral
When an object is in a position where disturbing it would require its COG to be raised it is in a __________ state of equilibrium. stable ie) brick laying on its long side.
When only a slight force is needed to disturb an object, it is in the state of __________ equilibrium. unstable ie)person standing on one leg; pencil on its tip
Force is a _________ quantity. vector
When an object's COG is neither raised or lowered when it is disturbed, it is in ___________equilibrium. neutral ie) ball rolling
The wider the _________ ____ _________, the more stable the object. base of support
If the LOG moves outside of the ________ ___ ________, the object becomes unstable. base of support
How does walking with crutches on only one leg change the LOG and BOS? Crutches increase the patient's BOS (makes it a triangle). The LOG will fall in the CENTER of the patient's BOS.
The lower the ________ ___ _________, the more stable the object. center of gravity (cog)
The _________ ___ _________ and the ________ ____ ________ must remain in the ___________ ____ __________ in order for an object to remain stable. center of gravity (COG) / line of gravity (LOG) / base of support (BOS)
Stability increases as the the base of support (BOS) is ___________ in the direction of the __________. widened / force
What does mass have to do with stability? The greater the mass, the greater the stability (remember the linebacker/halfback example)
What does friction have to do with stability? The greater the friction between the supporting surface and the BOS, the more stable the body will be.
People have better balance while moving if they focus on a __________ ________ rather than a ____________ ___________. stationary object / moving object (remember crutches example)
A ________ is rigid and can rotate around a fixed point when a force is applied. lever
The fixed point around which a lever rotates: axis (or fulcrum)
In terms of levers, the ________ is what causes the lever to move. force (or effort)
In terms of levers, the _________ must be overcome for motion to occur. This can include the ________ of the part being moved, the pull of gravity on the part, or an external weight being moved by the part. resistance (or load) / weight
The distance between the force and the axis: force arm (FA)
The distance between the resistance and axis: resistance arm (RA)
In this type of lever, the axis is located between the force and resistance: first class lever (FAR)
First class levers are designed for _________. balance
What is an example of a first class lever in the body? Name the force, axis, and resistance. The head sitting on C1 (atlas). Axis: C1 Force: exerted by muscle (trapezius for extension and sternocleidomastoid for flexion?) Resistance: weight of the head
When the force arm (FA) is __________ than the resistance arm (RA), there is a greater mechanical advantage. longer
In this type of lever, the resistance is in between the force and the axis: Second class lever (ARF) ie) wheelbarrow
Second class levers are designed for: power
What is an example of a second class lever in the body? Name the force, axis, and resistance. Plantar flexion lifting the body weight. force: force of the gastrocnemius muscle. resistance: body weight. Axis: ball of foot.
In this type of lever, the force is in between the axis and resistance: Third class lever (AFR) ie)rotating boat tied to dock
This is the most common lever in the body: Third class lever (AFR) ie) screen door on spring
The third class lever is designed for: motion
Name a third class lever in the body. Name the force, axis, and resistance. The biceps flexing the elbow. Axis: elbow. Force: upward force produced by biceps. Resistance: weight of hand
Mechanical advantage of a lever is determined by: dividing the length of the force arm (FA) by the length of the resistance arm (RA).
Feature of levers and machines that represents the relation between the force arm (FA) and resistance arm: mechanical advantage
Forces that are perpendicular or away from a surface (compression, traction, // forces (shear): normal forces
Opposing forces that are equal response to gravity or other force: reaction forces
A grooved wheel that turns on an axle with a rope or cable riding in the groove: pulley
What is the purpose of pulleys? To change the direction or the magnitude of the force
What are the types of pulleys? fixed and movable pulleys
What kind of lever does a fixed pulley act as? first class lever (FAR)
The type of pulley that is ONLY used to change direction (not magnitude): fixed pulley
What is an example of a fixed pulley in the body? The lateral malleolus acts a pulley, changing the direction of the force of the peroneus longus tendon.
The purpose of this type of pulley is to increase mechanical advantage: movable pulley
With this type of pulley, only half the amount of force is needed to lift the load because the amount of force gained has doubled: movable pulley
Created by: taranorwood