Knes 300 - Principles of Human Movement

1. Knes 300 - Principles of Human Movement • Course Objectives 1) Learn about the relationship between mechanical principles and moving bodies. 2) Apply your knowledge of these mechanical principles to well-known skills. Why analyze movement? - Minimize injury, maximize performance, optimize technique.

2. Knes 300 - Principles of Human Movement • Qualitative vs. Quantitative Approaches Qualitative Description of quality without the use of numbers. Quantitative Involving the use of numbers. Ex. Long jump - “That was a long jump” vs. the jump was 18 feet in length

3. Qualitative good poor long heavy flexed rotated dope tight Quantitative six meters three seconds fifty turns two players ten dollars 45 degrees 55 mph Qualitative vs. Quantitative Descriptors

4. Qualitative vs. Quantitative Descriptors Qualitative does not mean ‘general’. A man walking down the street may also be stated ‘a man is walking very slowly, appears to be leaning to the left, and is bearing weight on his right leg for as short a time as possible’. Both Q and Q are important in the biomechanical analysis of human movement and while researchers rely heavily on quantitative techniques, clinicians, coaches, and teachers or physical activities regularly employ qualitative observations of their patients, athletes, or students to formulate opinions or give advise.

5. Biomechanics • The science involving the study of biological systems from a mechanical perspective. • Statics and Dynamics are two major sub-branches of mechanics. Statics is the study of systems in a state of constant motion (at rest or constant velocity). Dynamics is the study of systems in which acceleration is present. • Kinematics - describes the appearance of motion. • Kinetics - the study of forces associated with motion (since F=ma then acceleration is important variable in kinetic analyses).

6. Chapter 1 - Sport Mechanics • Mechanical Principles • Technique • Traditional training methods • How to use this information

7. Chapter 1 - Sport Mechanics • Mechanical Principles Basic rules that govern an athlete’s actions. Ex. - Diver and gravity - optimal flight path - Wrestlers helped by gravity when getting opponent off balance - Ski jumpers using air resistance

8. Chapter 1 - Sport Mechanics • Technique - Patterns and sequence of movements that the athletes use to perform a sport skill. - Certain sports include a single skill such as discus throwing while tennis includes forehands, backhands, serves etc. - Each skill has a specific objective that with ‘good’ technique may be achieved with the highest degree of efficiency and success.

9. Chapter 1 - Sport Mechanics • Traditional training methods - Many coaches and athletes still follow old, traditional methods in their workouts. - Trial and error methods demonstrate a lack of understanding of mechanical principles. - Copying world champions disregard differences in physique, training and maturity. - Analyze performances and teach movement patterns that produce efficient technique leading to better performances.

10. Chapter 1 - Sport Mechanics • How to use this information - Learn to observe, analyze, and correct errors in performance. - Assess the effectiveness of innovations in sport equipment. - Assess training methods for potential safety problems. - Assess the value of innovations in the ways sport skills are performed. - Know what to expect from different body types and different levels of maturity.

11. Chapter 2 - Starting with Basics • Body weight • Mass • Inertia • Speed, Velocity and Acceleration • Gravity • Force • Vectors • Projectiles

12. Chapter 2 - Starting with Basics • Body weight - Newton’s third law states that “For every action there exists an equal AND opposite reaction” - Body’s mass pulls on the earth and the earth’s mass pulls on the body. Scale reading reflects this mutual pulling taking into account the earth’s gravitational pull. The earth’s gravitational pull varies according to location (the further AWAY from the center of the earth, the smaller the gravitational pull - the less you weigh).

13. Acceleration at Sea Level by Latitude

14. Chapter 2 - Starting with Basics • Mass - All objects that have substance or matter have mass. - The human body is composed of bones, muscles, fat, tissues and fluids all of which are substance or matter and have mass. - A heavyweight wrestler has more mass than a gymnast resulting in greater attraction between the earth and the wrestler than between the earth and the gymnast.

15. Chapter 2 - Starting with Basics • Inertia - Resistance to action or to change. - The desired of an object to continue doing whatever it’s doing - even when it’s moving. - All objects want to remain motionless, but if a force moves them, then they want to continue moving in the same direction at a constant speed.

16. Chapter 2 - Starting with Basics • Distance Total ground covered or traveled. A scalar. • Displacement As the crow flies - A straight line between the beginning and the end. Measured in cm, m, km. A vector • Speed Distance divided by time. 100 miles traveled in two hours average 50 mph. • Velocity Displacement divided by time. 100 meters south divided by 10 seconds equal 10 meters per second in the south direction.

17. Chapter 2 - Starting with Basics • Speed, Velocity and Acceleration - A sprinter running the 100 m in 10 sec has an average speed of 10 m/s or ~ 22 mph. This average speed indicates that the sprinter must have been going faster and slower at times to average the 22. - Velocity is a more precise description of speed - Giving it direction. Thus it includes both speed and direction - 20 mph due south. - The rate at which velocity changes is termed acceleration. It may be positive or negative.

18. Chapter 2 - Starting with Basics • Gravity - It is constant and it accelerates falling bodies at a rate of 32 feet per second per second or 9.8 meters per second per second. - It affects performance because the effects of gravity change the further you are from the center or core of the earth. - Ex. Mexico vs Moscow distances (elevations and equator).

19. Chapter 2 - Starting with Basics • Center of Gravity - The earth’s gravitational pull on the athlete is concentrated at the athlete’s center of gravity. - It represents the center of how the mass is distributed from head to toes. Muscle and bone are more dense and thus have more mass squashed into the space they occupy and thus the earth pulls more on those parts. - Ex. Males higher cog then females (hips) - Cog changes as limbs move and can be outside the body.

20. Chapter 2 - Starting with Basics • Force - A push or a pull that changes or tends to change the state of motion of an athlete or object. Force vector - refers to when the direction and amount of force is known.

21. + = + Force Vectors - Addition Tip to Tail = Parallelogram

22. _ Force Vectors - Subtraction _ = + + = Tip to Tail

23. Force Vectors - Multiplication x 2 = + = Tip to Tail

24. c a b What is a+b+c and 2c-a+3b and –c-b+a and a-b-c and –a-b-c? How many vectors can you add?

25. Motion • Linear • Rectilinear (skydiver, putt on level ground) • Curvilinear (parabolic trajectory, cannonball) • Angular (Rotary) • Rotates about an axis (wheels, spin dives, joints, curveballs) • General • Combination of linear and angular (sprinting)

26. Projectile Motion • To increase the horizontal distance (range) of a projectile you need to consider: • The velocity at release • The angle at release • The height at release

27. 5 4 3 2 1 0 Maximum height (m) 0 1 2 3 4 5 6 7 8 9 10 11 Range (distance) (m) Factors Influencing Projectile Trajectory This scaled diagram shows the size and shape of trajectories for an object projected at 10 m/s at different angles.

28. Chapter 2 - Starting with Basics • Newton’s Laws - Law of Inertia - a body will remain at rest or continue to move at a constant velocity unless acted upon by an external force. - Law of Acceleration - the acceleration of an object is directly proportional to the force causing it, it is in the same direction as the force and it is inversely proportional to its mass. - Law of Reaction - for every action there exists an equal and opposite reaction.

29. Chapter 3 - Getting a Move On • Action - Reaction • Momentum • Impulse • Work • Energy • Rebound • Friction

30. Chapter 3 - Getting a Move On • Action - Reaction This again is referring to Newton’s third law (Law of Reaction). Ex. Sprinter pushing against the blocks and the earth pushing back on the attached block to propel the sprinter forward. The force produced by the sprinter’s muscles overcome inertia and she accelerates. This acceleration is proportional to how much force she applies the the time frame over which it is applied, and it is inversely proportional to her mass.

31. Chapter 3 - Getting a Move On • Momentum A moving athlete/object is an example of mass on the move. Because a certain amount of mass is moving we refer to this as the a/o momentum. It describes the quantity of motion that occurs. To increase momentum the a/o needs to increase either its mass or its velocity or both. Important in sports that have collisions and impact - football, bowling, billiards. Increase mass by putting on muscle to increase power and speed. Car accidents experts reconstruct crash scenes by determining which car had greater momentum.

32. Momentum Testing the new Armed Forces barriers... From time to time someone asks what the concrete barriers are in front of controlled and secure buildings.  When told that the barriers will stop traffic, even trucks, from approaching the secure building I usually get a look of disbelief.  Looking for some footage like this to prove the point, in this test, the following parameters were used.  Read them and then watch the film. Truck = 65,000 lbs. Speed = 50 mph Kinetic Energy = 5.5 MILLION ft. lbs. Stopped in 24 INCHES!

33. Truck Video

36. Chapter 3 - Getting a Move On • Impulse To accelerate or to produce movement, an athlete needs to produce muscular force and create momentum. This force always takes time to produce and we refer to the application of force over a certain amount of time as impulse. Ex. Karate blow - Large force - short period of time. Bones 40 times stronger than concrete. Javelin throw - large force - long period of time. Strength and flexibility are important. High jump - large force - medium period of time. Not a full squat, but a quarter squat and rocking over the heel and backwards lean increase the amount of time over which to produce force.

37. Chapter 3 - Getting a Move On • Conservation of Linear Momentum Total amount of linear momentum of colliding bodies will be the same before and after the collision. If one body gains momentum then the other must lose momentum. Collisions cannot create or dissipate linear momentum but rather transfer it from one object to another. m1v1 + m2v2 = (m1 + m2) (v)

38. Conservation of Momentum • In the absence of external forces, the total momentum of a given system remains constant. A 90 kg hockey player traveling with a velocity of 6 m/s collides head-on with an 80 kg player traveling a 7 m/s. If the two players entangle and continue traveling together as a unit following the collision, what is their combined velocity? Known: m1= 90 kg m2=80 kg v1= 6 m/s v2= -7 m/s m1v1 + m2v2 = (m1 + m2) (v) (90 kg) (6 m/s) + (80 kg) (-7 m/s) = (90 kg + 80 kg) (v) 540 kg m/s – 560 kg m/s = (170 kg) (v) - 20 kg m/s = (170 kg) (v) v = 0.12 m/s in the direction of the 80 kg player’s original direction of travel

39. Chapter 3 - Getting a Move On • Work Mechanical work defined as force times distance. Ex. Filling shelves, throwing the javelin, ball slowed by turf, lifting weights. Different from physiological work in that for MW the object needs to move. A static or isometric contraction would involve PW but not MW. Unit is the Joule.

40. Chapter 3 - Getting a Move On • Power The rate at which work is done. It may be expressed as P = W/t or P = F x V In the metric system unit for Power is the watt Which is equivalent to 1 joule/second

41. Chapter 3 - Getting a Move On • Energy Defined as the capacity of an a/o to do work. Mechanical energy has three forms. Kinetic, Potential and Strain energy. Kinetic - moving energy KE = ½ * m * v2 Potential - location/position energy PE = m * g * h Strain - stored energy

42. Chapter 3 - Getting a Move On • Conservation of Energy As a diver begins to fall towards water her potential energy is transformed into kinetic energy. A ball thrown into the air has both kinetic and potential energy throughout its flight or parabolic trajectory Ex. Rib cage testing device for crash dummies.

43. Chapter 3 - Getting a Move On • Rebound When objects/bodies separate (move apart) after a collision or impact occurs. Angle of incidence and angle of reflection/rebound measured with respect to the vertical. Coefficient of elasticity/restitution refers to the degree (amount) of recoil/bounce that objects have. The greater the bounce the greater the coefficient (value between 0 and 1) with 0 signifying a completely inelastic object and 1 signifying a completely elastic object.

44. Angle of Reflection/Rebound Incidence Rebound

45. Chapter 3 - Getting a Move On • Rebound Affected by temperature and rebounding surface. Heat causes balls to bounce more while artificial turf also will cause a greater bounce.

46. Chapter 3 - Getting a Move On • Friction Force that occurs when an object moves or tends to move while in contact with another object. Reduce - wax skis, curling, bowling lanes Increase - rough gloves, cleats

47. Mechanical Behavior of Bodies in Contact What is friction? • force acting over the area of contact between two surfaces • direction is opposite of motion or motion tendency • magnitude is the product of the coefficient of friction () and the normal reaction force (R); F = R

48. Chapter 3 - Getting a Move On • Friction Three types - static, sliding and rolling. Static - seen in resting bodies, resists initiation of movement. Sliding - force that develops when two objects are sliding past each other. Rolling - when round object rolls past another. Factors affecting friction: forces pressing two surfaces together, nature (texture) of surfaces, actual contact area.

49. Chapter 3 - Getting a Move On • Friction Pressure = Force / Area One box exerts greater pressure against the floor than the other, thus squashing the microscopic irregularities found even on the smoothest of surfaces and by so doing it creates the same contact area as the other box.

50. Dynamic Fk = kR Static Fm = sR Friction Applied external force Mechanical Behavior of Bodies in Contact For static bodies, friction is equal to the applied force. For bodies in motion, friction is constant and less than maximum static friction.