Download What Should We Know By Now? Why Kinesiology is important to

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What Should We Know By Now?
Why Kinesiology is important to your field (specifically)
Basic Kinesiology Terms: qualitative/quantitative, kinetics/kinematics, scalar/vector quantities,
force/weight mass/matter, distance/displacement, velocity/speed volume, static/dynamic, mechanics,
efficiency/effectiveness
All bones in body (name, location, function, basic structure)
Properties of bones, articulations, muscles
Factors: influencing bone development, joint mobility/stability, force production
Planes, axes, joint motions, range of motion (ROM)
Muscle fiber types, GTO’s, SEC, Muscle spindles, Motor Neurons, Motor Units
Skills be able to view a picture/motions and determine joint involvement, motion, degrees of movement,
plane/axis
Chapter 3 Basic Biomechanical Factors & Concepts
We will now view the body as if it were a machine.
“Mechanics”
“Biomechanics”
Mechanics in the Body
Musculoskeletal system may be thought of as a series of simple machines
used to increase mechanical advantage
Machines function in four ways
o balance multiple forces (see saw)
o alter resulting direction of the applied force (pulley)
o enhance force in an attempt to reduce force needed to overcome a resistance (wheel barrow)
o enhance range of motion & speed of movement so that resistance may be moved further &/or
faster than applied force (shovel)
 primarily how the human body functions
3 Types of Levers (p. 72)
First-Class Levers
o Produce balanced movements when axis is midway between force & resistance (e.g., seesaw)
o Mechanical advantage in speed & range of motion when axis is close to force (scissors vs metal
cutters)
o Mechanical advantage in force production when axis is close to resistance (crowbar)
o First-Class Levers in the Body
 Head balanced on neck in flexing/extending
 Elbow extension in triceps applying force to olecranon (F) in extending the forearm (R)
at the elbow (A)
Second-Class Levers
o Mechanical advantage in force production, since a large resistance can be moved by a relatively
small force (FA is always > RA)
o Wheelbarrow, Nutcracker, Loosening a lug nut
Second-Class Levers in the Body
o Plantar flexion of foot to raise body on toes where ball (A) of foot serves as axis, ankle plantar
flexors apply force to calcaneus (F) to lift resistance of body at the tibial articulation (R) with
foot
o Relatively few 2nd class levers in body
Third-Class Levers
o Most common in human body
o Mechanical advantage in speed & range-of-motion movements
o
o
o
o
(RA is always > FA)
Requires a great deal of force to move even a small resistance
Paddling a boat
Shoveling - application of lifting force to a shovel handle with lower hand while upper hand on
shovel handle serves as axis of rotation
o Biceps brachii in elbow flexion using elbow joint (A) as axis, biceps brachii applies force at its
insertion on radial bone (F) to rotate forearm up, with its center of gravity (R) serving as point of
resistance application
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Factors Influencing Force Transferred to Objects
Kicking, throwing, striking
Length of Lever & Torque
In body muscle forces pull bones around axis & create “torque”
Torque – a rotary force (force that moves around an axis)
o force x force arm
Weight of ball creates torque
o resistance x resistance arm
o wt. of ball x distance ball is from axis
o To lift ball, torque created when muscle contracts must > torque created from gravity pulling on
ball
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How Limb Length Affects Torque
Resistance (ball) = 5 lbs; Resistance Arm = 12 inches; Torque = 60 units
To hold ball still I need:
Torque = 60 units if
Force Arm = 2 inches; Force = ? F x FA = torque; 30 lbs
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How Limb Length Affects Torque
Resistance (ball) = 5 lbs; Resistance Arm = 18 inches; Torque = 90 units
To hold ball still I need: Torque = 90 units
Force Arm = 2 inches; Force = ?; 45 lbs
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Same applies to bats and rackets
Longer limbs create “mechanical disadvantage in force production”
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How Limb Length Affects Speed of Motion
However, objects held in longer limbs travel a greater distance in a given time period & so can move
with higher velocities or speeds
Tennis player can hit a tennis ball harder with a straight-arm drive than with a bent elbow because the
lever (including the racket) is longer & moves at a faster speed
baseball pitcher, golf, football punter, etc.
kids leg lengths in running
running speed (cycling rate)
While they will need more force to move limb, they have a “mechanical advantage in speed and ROM”
Effect of Angle of Attachment on Force
If small angle, most of the tension will produce a force pulling along the bone will tend to stabilize joint
stabilizing component
Closer to 90 angle will have a much larger rotary component of force
Muscle angles change throughout ROM and affects the ability to move objects
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For each muscle, some angles provide mechanical advantage, other angles provide less on an advantage
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Nautilus’s “cam”
1970’s Arthur Jones created resistance machines to try to follow strength curves called the “cam”
variable resistance
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Systems in Motion follow Newton’s Laws
Law of Inertia (1st Law)
A system in motion tends to remain in motion at the same speed in a straight line unless acted on by a
force
system at rest tends to remain at rest unless acted on by a force
Muscles produce force to start, stop, accelerate, decelerate & change the direction of motion
Inertia - resistance to action or change (resistance to acceleration or deceleration)
reluctance to change status; only force can change status
> mass of an object > its inertia
greater mass, more force needed to change an object’s inertia
Law of Inertia
Examples
Sprinter in starting blocks must apply considerable force to overcome his resting inertia
Runner on an indoor track must apply considerable force to overcome moving inertia & stop before
hitting the wall
Thrown or struck balls require force to stop them; Force is required to change inertia
Any activity carried out at a steady pace in a consistent direction will conserve energy
Any irregularly paced or directed activity will be very costly to energy reserves
Ex. handball & basketball are so much more fatiguing than jogging; a distance runner speeding up and
slowing down
Law of Acceleration (2nd Law)
 in acceleration is directly proportional to the force causing it and inversely proportional to the mass of
the body: A= F/M
or
F = MA
Acceleration - the rate of change in velocity ()
To attain speed in moving the body, a strong muscular force is generally necessary (Vf – Vi)/time
Mass - the amount of matter in the body
affects the speed & acceleration in physical movements
Application: athletes acceleration abilities
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Law of Reaction (3rd Law)
For every action there is an opposite & equal reaction
As we place force on a surface by walking over it, the surface provides an equal resistance back in the
opposite direction to the soles of our feet
Our feet push down & back, while the surface pushes up & forward
Force of the surface reacting to the force we place on it is ground reaction force
Application: Pose Method of Running; skateboarding, running on sand
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Homework
review websites on page 84; complete review, laboratory, and worksheet exercises pages 84-86
complete reading of chapter; re-organize notes, create note cards etc.
write down questions of material you are struggling with to ask next class
find a way to apply information to your life
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