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Final

# Biomechanics Final Review.doc

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Western University

Kinesiology

Kinesiology 2241A/B

Bob Vigars

Winter

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Biomechanics Final Review
Pattern: run jump ect, movement pattern
Skill: pattern adapted to a task
Technique: variations of a skill ex. Jump serve
Style: unique timing or specialized moves
Constraints: anything limiting can be human or event
Closed skill: predictable environment for example a free throw, you are using
biomechanical principles
Open skill: unpredictable, execution less ideal
Continuous: can be broken down into discrete but as a whole doesn’t have a definite
begging or end
OPO: is the goal of a movement, for example getting as high up as you can
Biomechanical principles: factors affecting muscle forces (length tension relationship
between muscles) momentum, radius of body parts, kinetic link being used, lift and drag
forces, angle of projection/attack/attitude, rebound and spin of an object, methods of
initiating body rotation
Analysis process: 1. divide into discrete parts 2. mechanical purpose of each part (each
parts opo) 3. biomechanical factors (acceleration, radius ect.) 4. biomechanical principles
to achieve BP 5. critical features necessary for movements of specific skill
Force arm: needs to be not inline with c of g because then you will not create any torque
on the body
Factors influencing movement: magnitude of net torque has a big effect, the amount
created will effect the inertial characteristics of the object in ways or its rotational inertia
or friction factors or the pathway available
Rotary motion: represented by a straight line which starts at the axis of rotation and then
draw it right out to where it rotates therefore you are drawing it out to where it rotates
therefore you are making the radius, both points have the same angle thus the same
angular distance but since the second has a greater linear distance it has a greater linear
velocity
Angular velocity: how fast a rotating body segment changes its position, measured in
radian or degrees/second, 1 radian = 57.3 degrees, either clockwise or counter clockwise
Angular acceleration: rare in human motion, it is equal to angular velocity plus torque, a
large change in angular acceleration causes a great change in angular velocity, where a
small change causes a s small change in angular velocity over a long time, it equal
change in angular velocity over change in time
Average angular velocity: time it takes for a body/segment/object to complete a motion,
useful in quantitative analysis of motion, it equals angular displacement/time, it is an
average for the entire time of the motion
Instantaneous angular velocity: the angular acceleration at a particular point in the ROM
it is equal to radius times angular acceleration, it determines the instantaneous velocity of
any point on a system, you take this off the tangent
R of rotation: symmetrical systems distance from axis of rotation to a precise point on a
rotating system
R of gyration: asymmetrical therefore most objects, distance from axis of rotation to a
point where all the mass is concentrated, it is I=mk(2) or I=mr(2), if mass is spread far
from axis it has a larger radius of gyration Angular momentumL L=inertia times angular acceleration, cant change without external
torque, I is the rotational inertia therefore the bodies resistance 2 change, changing the
inertia will change the angular acceleration drastically
Angular impulse: Tt it is the torque multiplied by time of torque applied, no external
torques can be applied while airborne therefore takeoff is very important, determines
amount of angular momentum created
Conservation of angular momentum: L-Iw, L will stay the same while airborne therefore
you can either change angular accerlation by changing the inertia (smaller position) or
opposite, think of the diver
Turntable demos: twists about longitudinal axis, spins about a-p axis as get smaller you
move faster
Throw pattern: object behind body, sequential for increased high end point velocity,
curvilinear path, mostly wheel-axle, open kinetic link (sequential from larger to smaller)
max distance or velocity, you create angular momentum during the initial seg of body
rotation
Push pattern: all segments behind object simultaneous to increase force, rectilinear path,
mostly lever motions, closed kinetic link, everything moves together
Constraints to throw/push continuum: mass of projectile, volume/size/shape/profile,
target area, strength/power/skill of person
Open kinetic chain: throw or kick, end segment free (e.g. hand) sequential movement
Closed kinetic chainL jump/push end segment restrained, simultaneous
Steps of throw: 1.proximal 2.distal lags behind 3. achieve either max distance for velocity
Magnitude of radius: is influenced by mass of object
Final velocity: final v of hand at the end will determine projective v, the radius is the
perpendicular distance from axis of rotation and release point, the kinetic link will also
effect as will the radius
Kinetic link characteristics: more massive segments at proximal end least massive at
distal end, initial motion caused by torque applied 2 base
Sequential motions: 1.proximal/massive self giving L 2. external T decelerates into
proximal segment 3. to conserve L next segment acceleration (has smaller k) no increase
in momentum just maintain velocity 4. Each successive segment acierates therefore
increase angular acceleration than previous segment due to both the radius getting smaller
and trying to maintain velocity
Airborne reaction rotation: if u initiate a rotation about an axis it will happen opposite
direction at same axis (law of conservation)
Lever motions: flexion/extension/protraction/retraction/abd/adduction. Force creating
Wheel-axle: medial/lateral rotation, prontation/supintion, inversion.eversion, muscle
torque rotates a bone which becomes an axle, wheel is adjacent segment position at an
angle 2 the axle, creates velocity
Mechanical purpose of PUSH: max force/max power (force x velocity) max accuracy
Push pattern + force activates: max strength movements demands simultaneous
segmental rotations, move in rectilinear path, minimize accerlation in movements 2 avoid
injury
Push pattern + power activities: need both force and velocity to move fast, need higher
force in a short time Power in jumping movements: body into space via segmental rotations, need large force,
at take off c of g has high vertical velocity and moderate horizontal velocity and opposite
for opposite goal
Jumping motions: massive segments at end of chain (open ends) small at closed end,
force through c of g, shoulder flexion, trunk extension and extension of legs
Accuracy with velocity: consistency in movements, straight line motion just before
release then rectilinear for short distance, curvilinear than flat will increase distance
Sequence of movements for over-arm: 1. step forward with contra-lateral leg 2. pelvis 3.
trunk rotation 4. transfer L to arm by stopping/reducing L in shoulder 5. shoulder
protection 6. shoulder medial rotation 7. elbow extension 8. wrist/hand flexion
Motion analysis: 1. segments involved 2. movements involved 3. sequence of moments 4.
muscles causing movements
Smaller/ lighter projectiles: allows greater # of segments contribute to performance
allows for larger radius and smaller segments can contribute more
Different performance errors: segmental positioning, sequence of movements/ time lack
of power/strength
Segmental positioning: beginners position more distal segment in front of proximal
Sequencing of movements: beginner may move segments in clocks rather than
overlapping each with adjacent segment therefore making it simultaneous not sequential
4 opo in projection: max horizontal distance (smaller than 45 degrees angle) max vertical
distance (over 45 degree) max accuracy and max accuracy with speed
Projection less than 45 degrees: long throw or jump
Drag: has profile (form) drag or skin friction/surface drag, always resistive but can be
motive
Profile/form drag: magnitude is proportional to area of leading edge of projectile, higher
pressure on leading side and lower pressure on trailing, suction on trailing side, can be
decreased by streamlining, indirect relation between magnitude of flow velocity and
pressure created
V horizontal: have air resistance and ground friction so you want to have a high velocity
or high hit of release but still lower than for vertical, greater projection angle the lower
the horizontal velocity
Vertical target: darts/archery, farther away needs more Vvert
Horizontal target: basketball gold
Aerodynamic drag fore: motion of air flowing past projectile, equal to projectiles velocity
but in opposite direction
Skin/surface drag: air sticks to projectile therefore rougher sticks more, secondary factor
influencing magnitude of drag
V vertical: height of c of g at takeoff plays a big role, location of fingers at take off
effects –greater distance from c of g to finger equals a higher jump, gravity is first
resistive than motive one arm down and one up has greater distance and will cause faster
rotation
Headwind: Vdrage + Vheadwind, increase flow velocity acting on body, increase total
flow velocity acting on body
tailwind Vdrag – Vtailwind, decrease flow velocity acting on body, increase flow
velocity acting on a body skin friction: most noticed at low velocity, rubb

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