Biomechanics

Principle of Force Summation

• This principle is the combination of forces produced by different parts of the human body
• In order to produce an optimal amount of force (maximum force summation), the body parts needed for a movement must be used in a sequential order and within a certain time frame

• The greater the number of joints used in a movement, the greater the applied force.
• The joint actions, however, must be used in a proper sequence without gaps or breaks in the movement. Joints supported by large muscles that are in the centre of the body should be used before the joints supported by small muscles that are found at the distal ends of arms and legs

Force summation

• Maximum force and momentum is produced when a person is able to use as many muscles as possible in the correct order
• Generally, force is produced by using the large muscles first which is then transferred to the smaller muscles to complete a movement
• The more body parts (joints and muscles) that are involved in completing a movement, the greater the force that is possible to generate and transferred to a skill or movement

Range of motion

• A synovial joint has a certain range of motion through which it can move
• Though a joint's range of motion, the muscles associated with that joint produce internal forces
• The greater the range of motion, the greater the force that can be generated

Order of body segments

• When forces are transferred between joints and body segments, they need to be transferred in a logical order or sequence
• For effective force summation, we need to use our large muscles to generate force the is transferred in sequence through progressively smaller and more distal (Further away) muscles

Timing of body segments

• Not only do we need to use body segments in the correct order, we also need to have correct timing. This allows for maximum transfer of force
• For this to happen, each body segment should be used when the one before it reaches it’s peak force
• This coordination maximises force production

In a tennis serve, list what order of the muscles should be used for a successful serve:

1. Leg
2. Hips
3. Torso
4. Shoulder/arm
5. Wrist/hand

What would occur if the movements needed to carry out tennis serve were not in order or timed correctly?

-If the movements needed to carry out the tennis serve were not in order or timed correctly, there wouldn’t be a lot of force used. Their movement will also be uncoordinated.

Task:

1. Place a small object on the ground, close to your feet.
2. Stand against a wall. Your back and glutes must be touching the wall. You can not bend your knees.
3. Try and pick the object up

This will be impossible because you cannot use the right order of body segments (muscles and joint) to complete the task.

1. Basketball
2. Shooting a free throw
3. Legs, Hip, Torso, Shoulder, wrist

3/4/17

LO: To demonstrate understanding of force summation

Quiz:

1. What two things are produced if muscles are used in the correct order and at the correct time? Force and Motion
2. What would be the outcome if an athlete does not use their muscles in the correct order? The movement will be uncoordinated and they will not be able to use a lot of force
3. In relation to Newton’s 2nd law - how could you make yourself run faster? By applying more force, because you cannot change your mass in the moment
4. How does newton’s 1st law relate to discuss?  The discuss will not stop moving unless acted upon by an external force or will remain stationary
5. What does F=ma relate to? Why? Second because the 2nd law says how the more mass and acceleration the more force are being used
6. Name 3 ways to ensure to ensure you are stable?  
1. By making sure your vertical line of gravity is within your base of support
2. Having lower centre of gravity
3. Having bigger base of support so the vertical line of gravity will remain inside
7. In relation to stability, what is an advantage of being shorter? Being shorter means the centre of gravity is lower making yourself more stable

Relate this graph to force summation in a forearm hit in tennis. Full sentence!

By using muscles and joints in the correct order and time, you will increase in speed or velocity building up momentum to produce more force

Questions

1. If you were to teach a Y7 student to throw a tennis ball, what muscles would you expect them to use and in what order? Legs, hips, torso, shoulder, arm, wrist
2. If the student wasn’t throwing very far after showing the to use their muscles order, what is a factor that would you have to look at in relation to force summations? The timing of using the muscles

5/04/16

Quiz:

1. State Newton’s 1st law. An object will stay stationary or will keep moving unless acted upon by an external force.
2. State Newton’s 2nd law. Amount Acceleration depends on the mass and the size of force being used.
3. State Newton’s 3rd law. For every action, there is an equal and opposite reaction.
4. Define force summation. Force summation is the sequence of which muscle and joints to use from larger to smaller on the right time.
5. How does the COG relate of BOS? Centre of gravity has a vertical line going straight down. Having that line inside the base of support makes a person stable.
6. How does the VLG relate to stability? If the VLG is within the base of gravity. That person is stable or balance. If it’s not, the person will be unstable or unbalanced

Newton’s 2nd law is about acceleration. The size of acceleration depends on the mass and the amount of force being used. The movement I’m discussing is a football kick. Newton’s 2nd law relates to a football kick by having the right amount of force for the ball to reach its destination. The more force i put into the ball, the greater the acceleration. If I put less force, the lesser the acceleration. The bigger the mass of ball being kicked, the more force is needed for the ball to accelerate.

Newton’s 1st law is about how and object will remain stationary or will keep moving at a constant speed unless acted upon by an external force. The movement I’m discussing is a football kick. A football will remain stationary unless acted upon by an external force which in this case is me kicking the ball. The ball should keep moving at a constant speed but due to an external force like air resistance and friction of the grass. The ball will keep on decelerating into a stop.

Projectile Motion

A Projectile is..

• Any object that flies through the air e.g. your body on a trampoline, a ball released from your hand, a fruit falling from the tree

Projectile motion is …

• The way that a projectile moves through the air

Q. What are the projectiles that we have in sport

A. a shuttlecock, any kind of ball used in sport

Gravity

As weight increases, the effect that gravity has on the projectile increases

What does gravity actually do?

Gravity pulls everything to the core of the earth.

AIr resistance

Is affected by 4 different things

1. Surface area (Increase, so does air resistance)
2. Surface type (Rought, increased air resistance)
3. Speed increases, increases air resistance
4. Weight decrease, increased air resistance

Angle of release

A low angle will have less time in the air to travel

A high angle will use up too much force going high and not enough for distance

An angle in between of 45˚ will have the perfect combination of distance and time in the air to travel

Height and speed of release

Height of release

• The higher an object is released the more time it has in the air to travel

Speed of release (velocity)

• The faster an object is travelling before it is released, the further it will go

Levers

• Used when force is applied.
• Can be divided up into 3 different parts:

1. Fulcrum - pivot point that the movement happens (normally the joint)
2. The load (effort) - weight that needs to be moved
3. The force (output) - the place that the force is applied. It is the effort of the muscle contracted.
4.