Slide 2 We define motion as the action or process of change in
position. Movement is a change in position from one point to
another. Two things are necessary for motion to occur Space (space
to move in) Time (time during which to move) Slide 3 Two Types of
Motion Linear: motion in a straight line. Force generated by
athletes muscles. Ex. Sprinter running down track. Rotational:
movement about an axis Force is off centre resulting in rotation
Body or body part spins around an axis. Ex. Ice skater in spin.
Slide 4 Seven principles are grouped into four categories: 1.
Stability 2. Maximum Effort 3. Linear Motion 4. Angular Motion
Slide 5 Stability The ability to maintain ones balance is crucial
in sport. Principle #1 The lower the centre of mass, the larger the
base of support, the closer the centre of mass to the base of
support, the greater the mass, the more stability increases. Slide
6 Centre of mass point at which a person or objects mass is
concentrated. Line of gravity vertical line passing down through
centre of mass to ground Base of support area between the
supporting limbs. Slide 7 Maximum Effort Principle #2 The
production of maximum force requires the use of all the joints that
can be used. Athletes should perform slower, controlled movements
and high intensity. Body segments usually move at the same time.
Slide 8 The more joints used in a movement the more muscles
contracting = more force exerted. Football kickers (soccer style)
use one more joint movement (hip rotation) to provide greater
force. Slide 9 Slapshot in hockey involves the legs, shoulders,
arms and stick. Leaving out one joint would reduce the shots force.
Slide 10 Principle #3: The production of maximum velocity requires
the use of joints in order from largest to smallest. Larger, slower
joints start the movement and faster joints contribute once the
preceding joint reaches peak speed. The aim is to reach maximum
velocity of movement at impact or release. Slide 11 Maximum
velocity can be achieved by combining the speed of previous
movements and transferring this speed to the final segment or
implement hand, foot, stick etc. used to propel another object.
Slide 12 Examples Basketball jump shot large leg muscles begin
motion then other joints in sequence pelvis, trunk, shoulder,
elbow, wrist and fingers on follow through. The speed at the end of
a body segment or implement is directly proportional to the
implements length. Golfer use longer club to hit ball farther Slide
13 Momentum is amount of motion an athlete or object has developed.
Linear momentum is amount of momentum developed in a straight line.
Impulse: the application of force over a period of time that
results in a change in the amount of momentum an athlete or object
has. Slide 14 Joint range of motion is amount of movement at a
joint. Streamlining: is minimizing the surface area of an object in
the direction of motion and making this surface as smooth as
possible so that the flow of water or air past the object is smooth
Slide 15 Principle #4: The greater the applied impulse, the greater
the increase in velocity. If a skill requires maximal application
of force, the joint should be moved through a larger range of
motion. Force is applied for longer and impulse is greater. Ex.
Player jumping the highest is one who bends their knees the
deepest. leg strength Slide 16 Often occurs in reverse absorption
in catching or controlling a puck or ball. Momentum is dissipated
over time or distance through absorption Prevents injuries as well
Landing. Ex. Catching a ball, move hands inwards to increase time
force is applied. Slide 17 Principle #5: Movement usually occurs in
the direction opposite that of the applied force. Newtons 3 rd Law
every action has an equal and opposite reaction. When an athlete
pushes against any playing surface or piece of equipment. When the
athlete exerts a force the surface (water, ground ice) pushes back
with the same force and in the opposite direction. Spearing
Injuries Slide 18 Some forces operate in directions opposite that
of movement. Air and water resistance are important factors in many
sports. Skiing, speed skating, swimming, cycling Slide 19 Counter
by streamlining. Change body position to decrease air resistance
speed skater Swimmers full body swimsuit streamline body position
for skiers cyclist helmet position Slide 20 Angular Motion Angular
motion plays a key part in all sport. Circular motion that occurs
around an imaginary line called the axis or rotation. Moment of
force or torque. Slide 21 Principle #6 Angular motion is produced
by the application of a force acting at some distance from an axis,
that is, a torque. Athletes are concerned about Three kinds of
torque rotations of entire body off centre force rotation of
individual body segments muscles produce torque rotation of
projectiles impart spin. Slide 22 Injuries from torque - pitcher
shoulder Opponent imparts torque off centre force to knock athlete
off balance. E.g. tackle, check Sumo vs Rampage Slide 23 Principle
#7 Angular momentum is constant when an athlete or object is free
in the air. Once airborne an athlete will travel with a constant
angular momentum Ex. Diver rotates in air, momentum constant while
in air. Can change rate of rotation by repositioning limbs or
trunk. Hangtime
