BIOMECHANICS 2008

1. BIOMECHANICS2008 Title: Describe how functional anatomy and biomechanical principles relate to performing physical activity Level 2 Credits 4 Assessment Internal

2. This achievement standard requires demonstration of understanding of functional anatomy and biomechanical principles and how they relate to physical activity, through participation and/or observation

3. Lesson 1 Introduction to Biomechanics Lab - Practical lesson in small gym Lesson 2 Biomechanics Video and Motion Forces Lesson 3 Newton’s Three Laws - Law 1 Lesson 4 Newton’s Three Laws – Law’s 2 & 3 Lesson 5 Force Summation and Javelin Throw / Baseball Throw Lesson 6 Projectile Motion Lesson 7 Centre of Gravity, Balance, Stability and Equilibrium Lesson 8 Momentum, Transfer of Momentum and Conservation of Momentum Lesson 9 Phases of execution Lesson 10 & 11 Biomechanical principles are described as they apply to the sequence Levers Lesson 13 Revision Lesson plans

4. Defining Biomechanics Bio = body Mechanics = forces and motion “Biomechanics is the science concerned with how forces (internal & external) act on the human body and the effects these forces have on the motion of the body”.

5. WHAT IS BIOMECHANICS? • It involves the study of Forces and Motion involved in human movement, particularly sport performance. • In other words, biomechanics looks at what is the best technique for generating forces and producing the most efficient motion, in order to maximise sport performance (technique).

6. QUESTION???? • What is the best way to kick a rugby ball?, hit a golf ball?, throw a softball?, shoot a basketball?, hit a tennis ball?

7. Force = “is a push or pull that changes a body's state of rest or motion”. Internal Forces – generated within the body e.g.. forces due to muscle contraction External Forces – acting outside from the body e.g.. gravity FORCES

8. FORCES • In sport athletes primarily produce force within the body by contracting the muscles. Types of Forces Muscular Gravitational Frictional Aerodynamic Contact (ground or another body), Inertial Elastic Centripetal Centrifugal

9. TYPES OF FORCES • Muscular Force = due to the contraction of muscle. • Friction Force = due to two surfaces in contact with each other and the tendency of the two surfaces to oppose each others motion e.g.. mountain bike vs. racing bike tyres, sports shoe soles for various sports,

10. Gravity = is the downward acting force which attracts bodies to the centre of the earth. • Aerodynamic Force = (is a type of frictional force) due to air resistance, where particles of air resist the motion of a body through it. e.g.. use of aero bars for cycling, spin in a tennis serve, swing in bowling a cricket ball

11. Contact= the force involved in a collision of bodies or the ground. e.g.. Scrum or Tackling collisions in rugby, hitting or catching a cricket ball, running • Inertia = the force of an object due to its mass (whether moving or stationary) e.g.. catching a medicine ball vs. catching a volleyball, catching a cricket vs. tennis ball

12. Centripetal= force which is directed in toward the central axis of a rotating body. • Centrifugal= force directed outward away from the central axis of a rotating body.

13. Task • For each of the following, identify the forces acting and what or who they are acting on. • Kicking a soccer ball • Tennis serve • Throwing a javelin • A rugby tackle • Hitting a ball in cricket • Catching a medicine ball • Somersault in gymnastics

14. Newton's 3 Laws You Tube - Three Laws of Motion

15. Newton’s First Law The Law of Inertia (The 1st Law of Motion)

16. Newton's First Law of Motion - The Law of Inertia • A body will remain in a state of rest or in uniform straight line motion, unless acted upon by a force to change that state of rest or motion”. e.g.. Daniel Carter kicking a goal ball will remain at rest until Dan applies a force with his foot. The ball would travel in a straight line into the sky, but is acted upon by gravity and air resistance (wind) to change its motion

17. Newton's First Law of Motion - The Law of Inertia • Moving Inertia An object in motion tends to remain in motion and to travel in a straight line with uniform velocity unless acted upon by some external force. • Stationary Inertia An object at rest tends to remain at rest unless acted upon by some external force.

18. Newton's First Law of Motion - The Law of Inertia • Inertia In order to set in motion a body presently at rest, you need to overcome the tendency of the body to remain at rest. This tendency of the body to remain at rest is called it's stationary inertia. The applied force must overcome the body's stationary inertia for motion to occur. If the force is not great enough to overcome the body's stationary inertia the body will remain at rest.

19. Inertia • A very heavy Barbell has stationary inertia, A large force overcomes this and action occurs. The heavier barbell has greater stationary inertia, force cannot overcome this, motion does not occur and barbell remains at rest.

20. Inertia An object in motion tends to remain in motion and this tendency is called the body's moving inertia. A force must overcome the body's moving inertia in order to alter the body's motion. The motion of the basketball is altered, i.e. the ball is deflected when a force is applied by the hand.

21. Task • Passing and catching different sized medicine balls • Why is more force required to move the larger mass medicine ball? • List 3 examples where the principals of stationary inertia and moving inertia are important aspects of the sport

22. NEWTONS 3 LAWS OF MOTION The Law of Acceleration (The 2nd Law of Motion)

23. Newton's Second Law of Motion = The Law of Acceleration • The acceleration (change in motion) of a body is proportional to the force causing it, and the change takes place in the direction that the force acts. • Newton's Second Law of Motion, the law of acceleration can be expressed as: Acceleration = force / mass

24. Newton's Second Law of Motion = The Law of Acceleration When a body is acted upon by a force...... • The greater the force, the greater the acceleration. • The smaller the mass, the greater the acceleration. • The change in motion takes place in the direction in which the force is applied.

25. NEWTONS 3 LAWS OF MOTION The Law of Action-Reaction (The 3rd Law of Motion)

26. Newton's Third Law of MotionLaw of Action Reaction • Newton's Third Law of Motion states that “ “For every action, there is an equal and opposite reaction.”

27. Newton's Third Law of MotionLaw of Action Reaction For every action there is an equal and opposite reaction; • A force acting anywhere always has a force equal to that acting in the opposite direction • Forces work in pairs opposing one another • The initial force (action force) is opposed by a second force (reaction force) • Three Laws Summary

28. Force Summation • Force generation by the body is explained in terms of force summation the sequential acceleration of body segments, timing of body parts, Range of Motion (impulse) and Stretching Out. • The acceleration of body parts can be greatly improved through the process of FORCE SUMMATION. Force = mass x acceleration

29. Force Summation • In many sporting actions such as kicking a rugby ball, the desired movement is a combination of a number of body parts and the forces each body part generates. • These forces are added together through a sequence of body movements to generate a far greater force. • The correct sequence and timing of body parts permits the athlete to produce a greater force and therefore attain optimal velocity at release or contact.

30. Generating greater force • The body parts that are large muscle groups can generate large forces. The large force causes a large acceleration in that body part. When that body part reaches peak force then the body part has reached peak acceleration, after which the body part would start decelerating (slow down). • Peak force diagram (see teacher notes)

31. Force Summation & Timing • The sequence and timing of the body movements are extremely important in order to obtain maximum force generated by each successive body part and therefore maximise the efficiency of the movement. • Each successive body part should begin to accelerate when the previous limb has reached peak force, and therefore peak acceleration • Look at these examples; Girl throwMan throw • The fewer body parts used = less force

32. Force summation: ROM and stretching out • Impulse: Applying a Force for a longer period of time • Muscular force has to be produced when athletes want to get moving or they want to accelerate an object such as a soccer ball and give it momentum. The force that athletes apply always takes time. When athletes apply force to an object over a certain time , we say that the athlete has applied an IMPULSE to the object. IMPULSE = FORCE x TIME (force is applied for) • The longer the time the force is applied for, the greater the impulse. • Athletes can apply an impulse to their own bodies or to another athlete or to an object.

33. Example of ROM • Javelin • The combination of force and time depends on the needs of the skill and sport. Some skills, such as punches in boxing, require tremendous forces applied over a very short time frame. Other skills like throwing a javelin require forces applied over a longer timeframe. An expert javelin thrower accelerates the javelin by pulling it from way behind his body and releasing it far out in front. Long arms are beneficial as is a backward lean entering the throw position, why? The athlete applies the force for a long period and therefore more overall force is produced. • To do this an athlete will increase the range of motion, which allows them to apply the force for a longer period of time. • Javelin throw

34. Some working examples Use these clips to apply the principles of force summation we have just discussed Carter kick Tennis serve Tennis Serve 2 Hammer throw Caber toss

35. Motion Forces produce three types of motion: • Deformative Motion: changing the shape of the body • LinearMotion : moving a body from one place to another in a straight line. • AngularMotion: or rotation , this is where the body rotates or spins about an axis (either internal axis or external axis)

36. Linear Motion • Where movement occurs in a straight line. During translation, all parts of a body move through the same distance in the same direction in the same time.

37. Angular Motion During angular motion or rotation all parts of a body move in a circular path around a central axis moving through the same angle, in the same direction in the same time.

38. Angular Motion There are two types of axis of rotation: • Internal Axis this is when the axis passes through the body, usually at a joint, e.g.. the lower leg rotating a bending at knee joint occurs. • External Axis this is when the axis is outside the body, e.g.. a giant swing in gymnastics.

39. General Motion • In physical activity the motion that occurs is quite often a combination of linear motion and rotation. • General motion can be described as linear movement of the whole body that is achieved due to the angular motion of some of the body parts.

40. Projectile Motion • Projectile: Any body that is released into the air becomes projectile and the motion of the projectile is governed by a number of factors

41. Forces influencing projectile motion Propelling Force Gravity Air Resistance

42. Propelling force (force at impact or release) The most important force affects the projectile in how far and/or how high it travels.

43. Gravity • Acts equally on all objects, accelerating the object towards the ground. • Gravity acts on the vertical component of the objects motion

44. Air resistance • Air particles through which the object travels, opposes its forward motion. • Air resistance opposes the horizontal component of the projectiles motion. • The lighter the object or the larger its surface area, the more it is affected by air resistance. • Air resistance also increases with speed. e.g. a golf ball drive is more affected than a chip shot onto the green.

45. Air Resistance

46. Quantifying Motion • Having identified the types of motion a body can have; biomechanists need to then quantify (measure) the motion (i.e. describe motion in terms of certain quantities) in order to calculate the forces acting. This information can be used to compare and analyse the efficiency of the motion and movements of the athlete. • When we talk about the motion of a body or object we say it moves through a certain displacement (or distance) in a certain time interval. (i.e. it has a certain velocity). If that velocity is changing then the is undergoing acceleration or deceleration

47. Measuring your motion • See handout and do practical

48. Factors influencing the Flight Path or Trajectory of a projectile Velocity of release Angle of release Height of release Spin

49. Velocity of release • The speed at which the projectile leaves the propelling force (bat if hitting, hand if throwing, ground if jumping)

50. Height of release • Relative to the height at which the projectile lands, whether it is above or below the height at which the projectile was released.