KINESIOLOGY - Biomechanics

What are the 3 phases of movement

preparation, execution, and follow-through

Describe preparation

body prepares to perform a skill (proper prep to execute properly. For example, bending knees before a jump starting to get into position to be able to produce force

Describe execution

This phase generates momentum and proper technique to carry out the skill. (jumping off the ground)

apply the correct amount of force at the critical moment

main movement

Describe follow-through

body continues with momentum but begins to decelerate and re-estabilish balance (landing jump with bent knees or finishing a race and still jogging afterwards).

Important for accuracy - if follow-through is too early or late= unstability

What are some examples of external and internal forces that affect movement?

external - gravity, wind resistance, surface friction. This can help or hinder movement

internal - when a muscle contracts, generates force to move the bone

Examples of external forces in real life

Beneficial - Skydiving (gravity), tailwind (wind blowing from behind - wind resistance), and soccer cleats (prevent slipping - friction)

Hinder - Climbing stairs, headwind, improperly waxed skis

examples of internal forces in real life

Leg extension and bicep curls

Newtons 3 laws of motion

first law - the law of inertia

second law - the law of acceleration

third law - the law of action-reaction

What is a force

a force is a push or a pull, in the context of the human body, it is always a pull

Describe the 1st law of motion, provide examples to illustrate

A body in motion tends to stay in motion and a body at rest tends to stay at rest unless acted upon by an external force

Give an example of the 1st law of motion

A curling rock

after a curling rock is released, (if it were sliding on a frictionless surface), it would continue to move indefinitely as long as no other forces acted upon it

What is inertia?

The property of matter that causes an object to resist changes in motion. The larger the mass, the larger the inertia, meaning the harder it would be to push this object over (because it has a larger ability to resist changes in motion)

Describe the 2nd law of motion and give examples to illustrate

F=ma

force is proportional to acceleration (when force is applied to something, it will increase its acceleration) and mass is inversely proportional to acceleration

more force , more acceleration

more mass, less acceleration

Give an example of the 2nd law of motion

Sled push:

If the force stays the same, the mass will increase by 2 and acceleration will decrease by a half.

Describe the third law of motion

For every action, there is an equal and opposite reaction.

What is an example of the third law of motion

Swimming

Swimmer accelerates forward because they push backward against the wall (action force), causing a reaction force where the water exerts the swimmer forwards

What are the 3 classes of levers?

Linear motion

Takes place when the body and its parts move the same distance, in the same direction, at the same amount of time

Angular motion

rotational or angular motion is movement around an axis

General motion

What are the first principle of biomechanics?

stability

the greater the mass, the lower the centre of mass to the base of support

the closer the centre of mass to the base of support, the stability increases

how does changing the mass, centre of mass, and base of support provide more or less stability

magnitude

size

mass

all materials that make up the human body

2nd principle of biomechanics

the production of maximum force requires the use of all possible joint movements to carry out the task

for weightlifting you start at the lowest joints, like the ankles and such and all the force continues to be produced all the way to the arms thru the legs and the rest of the joints

3rd principle of biomechanics

sequencing of joint rotation

production of maximum velocity (speed) requires the use of joints in order from smallest to largest

what are the 2nd and the 3rd principles used for?

maximum effort to carry out maximum power and efficient movement

What is the 4th principle of biomechanics?

The impulse-momentum relationship

the greater the applied impulse, the greater the increase in velocity

the greater the pushing force and the greater amount of time to which it is applied to the ball, the greater impulse

what is momentum?

mass x velocity ( p=mv )

an object in motion has momentum

What is an example of how an athlete uses momentum?

Running start to a jump serve or long jump to provide more pushing force over a greater amount of time for more impulse overall.

What is principle 5 of biomechanics?

The direction in which movement usually occurs

• movement usually occurs in the direction opposite that of the applied force

What law of motion does principle 5 relate to

3rd law - for every action, there is an equal and opposite reaction

What is principle 6 of biomechanics

The effect of a force acting at some distance from an axis (angular motion)

angular motion is produced by the application of a force acting at some distance from an axis, that is by torque

what is torque

if an eccentric or off-center force is applied to a body, the force tends to make the body rotate about its axis, this turning effect is referred to as torque

what factors affect torque?

the applied force (rotation easiest when force is applied away from the axis)

the length of the lever arm (force applied perpendicularly to the arm)

the angle of the application of force

What is angular momentum?

angular momentum is the quantity of motion contained within an object or body.

angular momentum is the product of angular velocity and the extent to which the body resists angular motion

what is principle 7 of biomechanics?

the conservation of angular momentum

angular momentum is constant when an individual or object is free in the air

what factors can change the moment of inertia? what is the moment of inertia?

the resistance to angular motion is “the moment of inertia”

the farther a body’s distribution of mass to the axis of rotation, the greater is the body’s moment of inertia

ex. when a figure skater brings their feet in the spin, their mass is closer to the axis of rotation allowing more angular motion, but the moment of inertia becomes greater when the take their feet away from the body because the body’s distribution is further away from the axis.

how can you use principles 2 and 3 to help improve an athlete’s force generation in a swing or throwing skill

describe how changing the mass, centre of mass, and base of support can provide more or less stability

what is general motion

what is the class 1 lever

the fulcrum is located between the point of application of the force (the effort) and the resistance (the load) being moved.

what is the class 2 lever?

what is the class 3 lever

what is an example in the body of a class 1 lever

tricep — the load is at the back of the arm, fulcrum at the middle and effort at the front

what is an example in the body for a class 2 lever?

what is an example in the body for a class 3 lever?

what lever is predominately found in the body? why?