Chapter 3: Kinetic Concepts of Human Movement

Question 1

Biomechanics

Answer 1

the science that studies living things from a mechanical perspective

• Uses principles based around motion and forces to ultimately lead to improved performances, greater efficiency and accuracy at all sport levels

Question 2

How to Plan for a Biomechanical Analysis:

Answer 2

1. Identify the question of Interest (what the athlete is struggling to do)
   
   2. Determine the best perspective to view the movement from(front-on, Side-on, top view)
   3. Decide how many times the skill movement needs to be performed. Repeated observation can help in finding errors.
   4. Consider other factors(subjects clothing, visibility, setting, lighting)
   5. Visual or digital recording observations( digital recordings can mean movements can be replayed)
      
      6. Consider the characteristics of the performer(age, gender, anthropometry, skill level)

Question 3

Measurement Tools for a Biomechanical Analysis:

Answer 3

• Video Analysis: collect qualitative and quantitative data, can be reviewed repeatedly
• Apps such as Dartfish, Coaches Eye: can collect qualitative and quantitative data which allows video footage to be captured and analysed.

Question 4

Force

Answer 4

defined as a push or pull movement

- Force = Mass X Acceleration(F=ma)
- Force is measured in Newtons(N) which = 1kg of mass at 1m/s
    - E.g. Gravity acting on an object, someone kicking a ball

Question 5

Ways Force can effect an object:

Answer 5

• Changes the shape of the object(stretch, squish or twist)

- Moves the object(start moving from rest, speed up or down change direction)

Question 6

Types of Force:

Answer 6

• Friction
• air/water resistance(drag)
• Gravitational Force
• weight

Question 7

Friction

Answer 7

Friction is a force that resists the motion of one object against another

occurs when two substances are in contact with each other and they oppose the motions of each object

• The greater the mass of an object, the more friction and therefore greater force required to move it
• If the applied force is more than the level of friction, the object will begin to move

Question 8

How to increase friction in sports

Answer 8

• Studs in footy(increase surface area)
  
  • Magnesium chalk in gymnastics(increases friction between bars and hand)
    
    • Grips on cricket bats

Question 9

How to decrease Friction in sports

Answer 9

• Downhill skiing(wax on skies to make them travel faster)

- Lubricant on a bike chain(decreases friction around the bike chain)

Question 10

Air/water resistance (drag)

Answer 10

when an object or body moves through air or fluid, a drag force will be experienced

• Drag force opposes the direction of motion of an object, slowing it down

Question 11

Air / water resistance (drag) is affected by

Answer 11

• Air density
  
  • Cross-sectional area of the body
    
    • Speed of the object (faster speed, increased drag)

Question 12

How Athletes minimise Air/water resistance (drag)

Answer 12

• Technique(manipulating body positions)

- Clothing and fabric designs

Question 13

Gravitational Force

Answer 13

the downward force that acts on all objects of earth

• The acceleration of gravity on earth is 9.8m/s2

Question 14

Weight Force

Answer 14

a measurement that is affected by gravity and is measured by newtons

• Weight = Mass x Gravity(in N’s)
• If you were to measure your weight on a planet with different gravity, your mass would remain the same however your weight would change due to the differences in gravity

Question 15

Inertia

Answer 15

the tendency for a body or object to resist change to its state of motion (whether the object is moving or at rest) unless acted upon by an external force

- The greater the mass of an object, The greater the inertia, the greater the force needed to move it
    - If a force smaller than the inertia of an object is applied, there will be no change in the objects motion

Question 16

Momentum

Answer 16

the amount of motion an object has and its resistance to changing that motion

- Momentum = Mass x Velocity (in kg m/s)
- When two objects collide, they will move in the direction of the object with the greater momentum

Question 17

Conservation of Momentum

Answer 17

the total momentum before a collision is equal to the total momentum after a collision

• E.g. In golf, before contact is made, the ball has zero momentum and the golf club has all the momentum. After the shot is made, the momentum will be transferred onto the ball which will move off with high momentum and the momentum in the club will eventually decrease to zero

Question 18

Summation of Momentum / Force Summation

Answer 18

the sequential and coordinated movement of each body part segment to produce maximum velocity

• E.g. Throwing - momentum generated in lower body is transferred to the hips and trunk, then the shoulder and elbow, and finally to the wrist.

Question 19

Principals of Force Summation

Answer 19

• Use muscles that have the greatest inertia to begin with
• Recruit as many muscle groups as possible to generate more force
• Transfer momentum from one body part to the next when at maximum velocity
• Ensure a stable base to keep momentum
• Ensure there is an appropriate follow through to prevent unnecessary deceleration of body parts

Question 20

Impulse

Answer 20

• refers to the manipulation of an objects momentum by either increasing or decreasing the objects velocity
• Impulse = Force x Time
• A change in the momentum can result from a large force being applied over a short period of time or as a result of a small force over a long period of time
• E.g. Softball strike(Force > time) / Ball rolling over green(force < time)

Question 21

Newtons Laws of Motion

Answer 21

1st = Inertia
2nd = Acceleration(F=MA)
3rd = Action/Reaction

Question 22

Acceleration

Answer 22

the speed of a body’s initiation is proportional to the force applied to it and in the direction in which the force is applied

• To produce maximal force, acceleration and mass should be at its highest
• E.g. For a baseball bat, the higher the mass and the faster it can be swung, the higher force that can be transferred to the baseball
• However if the bat held is too heavy to be swung by an athlete, it is counterproductive as the person cannot accelerate it enough, therefore maximum force cannot be generated
• If the bat is too light, the player would be able to swing with maximum acceleration however due to the low mass of the bat, their force output will be still low

Question 23

Action / Reaction

Answer 23

for every action, there is an equal and opposite reaction

• Whenever an object exerts a force on one object, there will be an equal and opposite force exerted by the second object on the first
• E.g. In order for a soccer player to move to the left, force must be applied to their right
• E.g. In order to jump upwards, you must exert force downwards into the ground