Biomechanics Flashcards
What are the 5 phases of skill movement?
Preliminary, back swing, force-producing, critical instant, follow through
What are preliminary movements?
Prepare to perform the skill, getting into the ready position.
What does the backswing do?
Aid in force production, allows for force to be created.
What do force producing movements do?
Produce the force for the impact
What is the critical instant?
The movement at impact/release
What is the follow-through?
Recovery movements, continuation of all the previous movements
What are the biomechanical principals?
Stability Maximum effort (maximum force and maximum velocity) Linear motion (applied impulse and direction) Angular motion (angular motion and angular momentum)
Principle #1 Stability
Stable balance requires:
- Low centre of gravity
- Wide base of support
- COG within the base
- Large mass
Principle #2 Maximum Force
Maximum Effort
The production of maximum force requires the use of all joints that can be used.
Principle #3 Maximum Velocity
Maximum Effort
Human movement requires the use of all joints in order from largest to smallest.
Principle #4 Applied Impulse
Linear Motion
The greater the implied impulse , the greater the increase in velocity.
Principle #5 Direction
Linear Motion
Human movement occurs in the direction opposite of the applied force.
Principle #6 Angular Motion
Angular Motion
Angular motion is produced by the application of a force acting at some distance from an axis or a torque.
Principle #7 Angular Momentum
Angular Motion
Angular momentum is constant when an athlete or object is free in the air.
What is gravity?
A force that exerts a downwards pull on everything
What is the COG of a person?
Imaginary point where masses are concentrated (balance point)
What is the line of gravity?
A line passing straight down through the COG to the ground (perpendicular)
What is mass?
Measure of the resistance of the athlete or object to linear motion.
What happens with greater mass?
Greater resistance to motion
What happens with lower COG?
Higher stability
How do you lower COG?
Bend knees and waist
What does lowering the COG do?
Makes it more difficult for opponents to push them off balance.
What is the base of support?
The feet and the space between then?
What happens with greater area of BOS?
Higher stability
Where do we want COG to be? Why?
As close as possible to the middle of the BOS. For more stability.
What is the line of gravity related to stability?
If LOG falls out of BOS there is less balance
What happens with increased mass?
Increased stability
What is mass good for? Bad?
+ Makes it harder to fall of balance
- May affect speed
What happens with more external weight?
More stability problems
Why do athletes want to be unstable?
To increase ability to move more quickly in a certain direction.
What does dynamic balance do?
Maintains stability while moving
What is force?
Push or pull that causes motion
What is acceleration?
Rate of change of velocity
Newtons Laws
1-inertia
2-acceleration
3-action and reaction
How do you get maximum force?
Slower, controlled movements at a high intensity
How are the skills of maximum velocity performed?
Sequentially-large and slow to small and fast joints
What is good and bad with a longer implement?
+Greater speed at end of lever
- Takes greater force
- Less control
Preliminary movements of overhand baseball pitch
-Pivots on throwing arm leg and turns body sideways to batter
Backswing movements of overhand baseball pitch
- Swings stride leg upward while flexing pivot leg to increase stability
- Hips rotate backward even more and COG moves farther back from base
What do the preliminary movements of overhand baseball pitch do?
Bring the muscles of the hips and trunk to a position where they can contribute maximum force to the throw.
What do the backswing movements of overhand baseball pitch do?
From this position, the pitcher can use as many joints as possible and move them through a maximal range of motion to accelerate the pitching arm.
Force-producing movements of overhand baseball pitch
- Extending supporting led and driving body forward onto front foot
- Hips rotate to face batter
- Forceful rotation of hips and shoulders causes the trunk to rotate rapidly
- Speed is transferred to pitching arm when pitcher stops rotating trunk
- Shoulder is forcefully medially rotated with the upper arm at 90° to the shoulder
- Elbow is extended, forearm pronated, and some wrist flexion at release
Critical instant of overhand baseball pitch
When ball is released
- Body is fully extended, throwing arm is extended above shoulder and slightly in front of head
- Back leg is extended
- Trunk leans away from throwing arm
- Head leans to side away from throw
Follow-through of overhand baseball pitch
- Throwing arm continues from release down and across from of body (continue to lean forward)
- Throwing arm is relaxed and the velocity of the arm is dissipated over the greatest time and distance possible to prevent injury
Stationary motion
(Stable motion)
Occurs when body is balanced and there is no significant movement.
Linear motion
Movement of an object in a straight line. Described by how far and how fast.
Example of stationary motion
Handstand
Example of linear motion
Athlete on bobbled going down track
When is linear motion produced?
When forces are applied directly through the COG.
Angular motion
Occurs when the body or a part undergoes rotation.
Example of angular motion
Somersaults, spins
What is the result of application of force?
Angular/rotary motion OR translatory motion
Angular/rotary motion
Object turning about an axis OR object moving through an arc
Translatory motion
Whole object being moved from one location to another. Can be rectilinear (linear) or curvilinear.
Rectilinear (linear) motion
Movement of the object as a whole with all parts moving in the same direction, same distance, and uniform speed.
What does rectilinear (linear) motion involve?
The point of application of force being on a line perpendicular to the LOG and parallel to the surface being acted upon.
Curvilinear motion
Object moving in a curved (not circular) path from one place to another (parabolic curve).
What does curvilinear motion involve?
- Any projectile acted upon by gravity in which its motion goes from liner to curved
- COG of projectile following the parabolic curve and not changing in mid-flight unless a new external force is introduced
Which two types of motion are often found at the same time? What is this called? List examples.
Angular + transitory = general motion
- Wheels of car rotate to cause it to move forward
- Person rotates limbs to move forward
- Footballs
- Frisbees
Momentum
Amount of motion that an athlete has developed. Depends on mass and velocity.
How do you calculate linear momentum?
mass x velocity
Impulse
Application of force over a certain time to change the amount of momentum in an athlete/object.
Joint range of motion
ROM of a joint
Streamlining
Making athlete/object as smooth as possible so that the flow or water or air past it is smooth.
When the lines of flow are parallel.
How is streamlining achieved?
By minimizing the surface area facing flow and making it as smooth as possible.
What type of motion is all other types produced by?
Angular motion
Where is the axis of rotation when the whole body is rotating(cartwheel)?
The point of contact with the ground, so it may be always changing.
Where is the axis of rotation when airborne?
Through the COG
Angular velocity
Velocity of an athlete/object/body segment in angular version.
Moment (torque)
Tendency to rotate about an axis of rotation.
How is moment calculated?
magnitude of force x distance of weight from axis of rotation (radius)
Moment of inertia
Measure of resistance to angular motion.
How is moment of inertia calculated?
mr²
m=mass
r=radius (distance from axis of rotation)
Angular Momentum
Quantity of angular motion
When is angular momentum of interest?
When athletes are spinning freely in the air or want to control rotations on a low-friction surface.
How is angular momentum calculated?
moment of inertia x angular velocity
OR
(angular distance² /time)(mr² )
When does angular momentum for rotations need to be created? Why?
Before take-off because it is constant after.
How can athletes alter their angular motion?
Increase inertia to decrease angular velocity.
Decrease inertia to increase angular velocity.
When do athletes rotate?
When off-centre forces are applied to their bodies.
How can an object’s flight be made more stable?
By applying spin.
Why are irregularities on an object in flight?
It will set up turbulences, which will produce uneven forces, which creates an erratic flight.
High pressure on a ball
Low velocity where the layer of air on the ball is moving opposite air flow.
Low pressure on a ball
High velocity where the layer of air on the ball is moving in the same direction as air flow.
