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Ch 8 Biomechanics
Clinical Kinesiology Chapter 8
Question | Answer |
---|---|
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 |