1. Sporting activity cannot be defined purely as linear motion.
Angular Motion
Sporting activity cannot be defined purely as linear motion.
Even for the sprinter there is considerable angular motion.
The legs and arms are rotating about their particular axis.
With angular motion, resistance to change in motion depends not only upon mass, but also on the DISTRIBUTION OF THE MASS AROUND THE AXIS. This is called the moment of inertia of the object.
The closer the mass is to the axis (centre of gravity), the easier it is to turn.
RUNNING
It is easier to run by bending the legs on recovery, because it is easier for the quadriceps to lift a bent leg (lower moment of inertia) than one that is straight.
TENNIS
Children use smaller racquets because they can swing the smaller racquet more easily than the larger one. The junior racquet has a lower moment of inertia because it has a lower mass.
DELTOID RAISE STRAIGHT ARM VERSUS BENT ARM
Bent arm is easier because centre of gravity is closer to the axis making rotation easier. TRY IT AND SEE!
EDU2MP Movement Perspectives

2. Movement Axes When standing:
The vertical axis runs from head to foot through the body’s centre of gravity.
The frontal axis runs from side to side through the body’s centre of gravity.
The sagittal axis runs from front to back through the body’s centre of gravity.
Use one cocktail stick for each axis and show it on jelly baby sweets. Eat afterwards mmmm.
If the axis (cocktail stick) were not a pole but a sheet of card – discuss planes.
The transverse plane is a horizontal plane which divides the body into upper and lower halves.
The sagittal plane is a vertical plane which divides the body into right and left halves.
The lateral (coronal) plane is also a vertical plane and divides the body into front and back. DRAW!
EDU2MP Movement Perspectives

3. There are three axes of movement around which movement can occur.
Movement Axes
There are three axes of movement around which movement can occur.
Vertical
Horizontal
(Frontal)
Anterior/Posterior
(Sagittal)
EDU2MP Movement Perspectives

4. Angular Kinematics Angular distance and displacement When a rotating body moves from one position to another, the angular distance through which it moves is equal to the length of the angular path. The angular displacement that a rotating body experiences is equal in magnitude to the angle between the initial and final position of the body. Angular movement is usually expressed in radians where 1 radian = 57.3° Angular speed, velocity and acceleration Angular speed = angular displacement ÷ time Angular velocity = angular displacement ÷ time Angular acceleration = (final angular velocity - initial angular velocity) ÷ time Angular Momentum Angular momentum is defined as: angular velocity x moment of inertia The angular momentum of a system remains constant throughout a movement provided nothing outside the system acts with a turning moment on it. This is known as the Law Conservation of Angular Momentum. In simple terms, this means that if a skater, when already spinning, changes their moment of inertia (they move their arms out to the side) then the rate of spin will change but the angular momentum will stay the same.
EDU2MP Movement Perspectives