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Every body segment has what two things, as it relates to gravity?
- A center of gravity;
- Is acted on by the force of gravity
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What is the line of gravity (LOG) and what direction does it apply force?
- Downward direction of the force of gravity on an object;
- applies force vertically, towards the center of the earth
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What is the center of gravity (COG)?
- (FBC)
- The point of exact center around which the body freely rotates;
- Point around which body weight is equal on all sides;
- Point of intersection of the three cardinal body planes
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Where does the COG lie in the body?
Approximately anterior to the 2nd sacral vertebra when the body is in anatomic position
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Does the body's COG change?
Yes, it changes as the segments of the body move away from the anatomic position
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What is the based of support (BOS)?
Area of contact between the body and supporting surface
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How is balance maintained?
When the COG remains over the BOS.
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What is stability?
The firmness of balance, where the COG falls withing the BOS.
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How do you attain increased stability?
When the COG is closer to the BOS.
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How do you attain maximal stability?
When the COG is placed over the center of the BOS.
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What is the rotation of a segment of the body dependant on?
- The magnituide of the force exerted by the effort force and the resistance force;
- The distance of these two forces from the axis of rotation
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What does changing the torque do, in term of exercise?
Provides a method for altering the difficulty of an exercise when weight is applied.
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What does applying weight to an extended arm do? What happens if you move the weight closer to the body?
- Changes the COG of the arm to more distal positions, requiring greater muscular support to maintain the arm in a horizontal position.
- Moving closer to the body, less muscular effort is required.
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How do pulley systems in a gym work in terms of resistance?
They don't act in a vertical direction (like free weights), but exert effects that vary according to the angle of the application.
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What is distractive force, and why is it used?
- Weights applied to the extremeties that exert traction;
- Used to promote normal joint movement in rehabilitation exercies, but they can also be injurous or undesirable.
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What are the 4 types of motion?
- (TRVM)
- Translatory
- Rotary
- Velocity
- Momentum
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When does translatory motion occur?
- When a freely moveable object moves in a straight line when a force is applied on the center of the object;
- When the object is free to move in a rectilinear or curvilinear path, regardless of where the force is applied
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What does rotary motion occur?
- When a force is applied off center to a freely moveable object;
- When the object is free to move only in a rotary path, regardless of where the force is applied.
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What is velocity?
The distance traveled in a period of time
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What is acceleration, as it relates to velocity?
Refers to increasing velocity
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What is deceleration, as it relates to velocity?
refers to decreasing velocity
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What is momentum?
- The mathematical product of the mass and velocity of a moving object;
- M = mv
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What is a lever and how are they used?
- A rigid bar that revolves around a fixed point or axis (fulcrum);
- Used with force to overcome resistance
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What are the parts of a lever? Define those parts.
- Axis - pivot point between the force and resistance;
- Force Arm - distance from the axis to the point of application of force;
- Resistance Arm - distance from the axis to the resistance
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What is a first-class lever, and example in the body?
- The axis between the force and the resistance arm and the force arm may be greater than, smaller than or equal to the resistance arm.
- Acting like a seesaw;
- Neck
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What is a second-class lever, and example in the body?
- The resistance lies between the effort force and axis of rotation, and the force arm is greater than the resistance arm.
- Acting like the wheel of a wheelbarrow;
- Plantarflexion pushing off ground
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What is a thrid-class lever, and example in the body?
- The effort force lies closer to the axis of the lever than the resistance, and the force arm is smaller than the resistance arm;
- Every muscle of body serves as 3rd class-lever
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How do levers apply to the body?
- Joint = axis (fulcrum)
- Contraction of skeletal muscles around the joint = force
- Moving segment = resistance
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