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47 Cards in this Set
- Front
- Back
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Definition of linear momentum
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-A quantity used to describe the
change in a system’s state of motion -Vector -Measure of impact |
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Equation for linear momentum
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P=mv
Momentum= mass X velocity (kg m/s) |
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Equation for average force using linear impulse
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F(ave)= (mv final- mv initial) / change in time
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Definition of linear impulse
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Quantity to describe changes in
linear momentum |
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Equation for linear impluse
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Impulse= F*change in time
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Describe a 2nd class lever system
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Force----Load----Fulcrum
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COG of the body
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Can be inside or outside the body
DOES depend on the shape and distribution of body segments The point at which all the body's mass seems to be concentrated |
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Units of Torque
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Nm or ft-lb
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When a muscle contracts, the torque produced is affected by...
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The motive component of muscle force
The overall magnitude of the muscle force produced |
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What is the fuction of a pulley system
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to change the direction of the motive force in order to be at a better advantage for force
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What is the direction of a force component that is stabilizing a limb?
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parallel to the force arm (bone) and in the direction of the joint
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What is the direction of a force component that causes rotation of a specific limb segment around a proximal joint?
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Perpendicular to the force arm (bone) and in the direction of the limb segment
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Give an example of a tri-phasic firing pattern
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In lab, when we did the arm to chest thing
Any quick, goal-directed movements! |
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A springboard diver changes from pike to tuck...what happens the PATH of his COG
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It will not be affected (continue to fall straight toward the water) because he uses only INTERNAL FORCES of his body to do this
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How do you find the force exerted to keep something on a circular path
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F= (mv^2)/r
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Define electromechanical delay (EMD)
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The delay between the EMG electrical stimulation and the resulting measurable tension in the muscle
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State the type of muscle fibers that Henneman Size principle applies to and briefly describe in words what this principle states
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Type I, IIa, and IIb.
The fibers with the smallest soma are recruited before the ones with larger soma. |
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A forward rool occurs in the mover's __________ plane
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sagittal
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Give two examples of biarticular muscles
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gastrocneimus
biceps brachii |
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Consider mass and weight...which is scalar and which is a vector
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Mass is scalar
Weight is a vector |
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What are the three types of strength training exercises?
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Isometric
Isokinetic Isotonic |
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Isometric
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no change in muscle length
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Isokinetic
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constant angular velocity
NOT constant muscle speed |
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Isotonic
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equal tone/equal tension
accelerated movement |
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How do you find impulse?
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change in momentum
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What are some advantages of isokinetic devices
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-Therapist can control the velocity of the exercise
-Provides resistance as a percentage of force applied by the subject (accommadates for skeletal leverage, pain, fatigue -accurate measurement of strength, endurance, and power -resistance only when effort is applied |
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What are some DISadvantages of isokinetic devices
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-Tests groups of muscles rather than individual
-only concentric contractions -not sport or task specific movements -expensive and impractical |
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What influences the rotational inertia of a spinning body
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the distance r each body segment is away from the axis of rotation
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4 Sensory systems contributing
posture-relevant information |
Proprioception
Vision Vestibular Touch |
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What are the 3 levels of the motor hierarchy
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Voluntary Movements
Postural Reflexes Stretch Reflexes |
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Describe postural reflexes
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Involuntary
Slower than stretch reflexes Involve multiple muscles (antagonist) and cross-over Spinal cord and brain stem, up to cerebellum 70-120ms!! Stimulated by external force Sensed by proprioception, vision, touch, vestibular sense |
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Describe stretch reflexes
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25-60ms!!
Stimulated by sudden stretch of muscle. Involves one efferent and one afferent nerve pathway (monosynaptic) Spinal cord ONLY Sensed by proprioception only |
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What are the major postural muscles
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Abdominal
Paraspinal (lower back) Quads and hamstrings Tibialis and gastrocneimus |
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What does a force platform meaure and what is it used for?
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vGRF and CFP (center of foot prssure) to determine postural control and body sway
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Describe a 1st class lever system
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See saw (atlanto-occipital joint)
Force----Fulcrum----Load |
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Describe 3rd class lever system
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Most muscles in human body
Load^----Force^---fulcrum |
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Why are humans at an advantage for ROM?
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Human muscles are usually attached
close to the joint axis. Thus, when the muscles shortens, a relatively small change in muscle length causes large linear displacement of the limb center of mass |
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The Muscle-skeletal System
Key Concept No. 1 |
Human movement is the result of the
application of internal (muscular) and external forces (e.g., gravity) to the body. => skillful movement is NOT the sole result of muscular innervation. |
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The Muscle-skeletal System
Key Concept No. 2 |
Only a portion of the generated
muscle force translates into visible limb motion. The remaining portion either stabilizes or destabilizes the joint. |
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The Muscle-skeletal System
Key Concept No. 3 |
Given muscular redundancy, some
muscles provide large amounts of rotary force, while others function as joint stabilizers. Change in limb orientation or joint angle can change the function of the muscle during movementGiven muscular redundancy, some muscles provide large amounts of rotary force, while others function as joint stabilizers. Change in limb orientation or joint angle can change the function of the muscle during movement |
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The Muscle-skeletal System
Key Concept No. 4 |
To a large extent, the human
musculoskeletal system consists of third class levers with short muscle force arms. => mechanical disadvantage for force. |
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The Muscle-skeletal System
Key Concept No. 5 |
Given that many muscles are
attached closely to the axis of rotation, small amounts of muscle shortening cause large distal limb displacements. => advantage for ROM and speed. |
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Factors influencing muscle torque
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Number of fibers
Fiber arrangement Angle of attachment Length of force arm |
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What does the force platform measure?
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The electric analog signal is converted into digital data yielding six
measurements: !Forces generated: < Fx < Fy < Fz !Torques: < Tx - in the frontal plane < Ty - in the sagittal plane < Tz - in the transverse plane |
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What can you derive fromt he force platform measurements? (Force and torque in the three planes)
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< Center of foot pressure (CFP)
< CFP sway path < CFP sway area |
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What is postural control?
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In biomechanical terms POSTURAL CONTROL implies
keeping your COG within the base of support. !A loss of POSTURAL CONTROL implies that the COG left its base of support. |
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Pedar systems can be used for gait analysis. What variables are used to analyze gait?
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Stance phase
Swing phase Double support time Nonsupport time |
