Lesson 13.1 APPLIED BIOMECHANICS

Transcription

1 Lesson 13.1 APPLIED BIOMECHANICS ~ ~ ~ TOPICS COVERED IN THIS LESSON (a) Reviewing Biomechanical Principles (b) Functional Movement and Movement Efficiency 2015 Thompson Educational Publishing, Inc. 1

2 Focussing Question ~ ~ ~ What are some purposes for the biomechanical analysis of functional movement? 2015 Thompson Educational Publishing, Inc. 2

3 Human Movement Analysis Biomechanical concepts and principles provide a basis for human movement analysis. The goals of movement assessment vary depending on the desired outcome; some goals include: To fine-tune an athlete s movement techniques to reduce the risk of injury or to improve performance; To modify a worker s movement patterns to delay the onset of fatigue on the job; or To provide feedback about a person s progress in regaining movement proficiency while undergoing rehabilitation Thompson Educational Publishing, Inc. 3

4 Review of Biomechanical Principle 1 Maintaining and controlling our balance is an important aspect of movement proficiency. How stable or balanced an individual is depends on four factors, as stated in biomechanical principle 1. Principle 1: The greater the mass, the lower the centre of mass to the base of support, the larger the base of support, and the closer the centre of mass is positioned to the base of support, the more stability increases Thompson Educational Publishing, Inc. 4

5 Review of Biomechanical Principles 2 & 3 In many activities, we must exert maximum effort in order to accomplish a specific task. Exerting maximum effort involves biomechanical principles 2 and 3: Principle 2: The production of maximum force requires the use of all possible joint movements that contribute to the task s objective. Principle 3: The production of maximum velocity requires the use of joints in order from largest to smallest Thompson Educational Publishing, Inc. 5

6 Review of Biomechanical Principles 4 & 5 Biomechanical principles 4 and 5 are related to linear motion motion that takes place when a body or its collective parts move the same distance, in the same direction, in the same amount of time. Principle 4: The greater the applied impulse, the greater the increase in velocity. For example, by applying a large impulse, a hitter in cricket, tennis, and baseball can strike the ball so that it leaves the bat with greater velocity. Principle 5: Movement usually occurs in the direction opposite that of the applied force. For example, in making a cut, a soccer player will push his or her foot against the ground to make a change in direction away from an opponent Thompson Educational Publishing, Inc. 6

7 Review of Biomechanical Principles 6 & 7 Biomechanical principles 6 and 7 are related to rotational motion. Also called angular motion, rotational motion is movement around an axis. Our bodies have many such axes they are called joints. Joints serve as axes of rotation for the movement of our limbs. The human body as a whole can also rotate freely about one (or more) of the three anatomical axes. Principle 6: Angular motion is produced by the application of a force acting at some distance from an axis; that is, by torque. Principle 7: Angular momentum is constant when an individual or object is free in the air Thompson Educational Publishing, Inc. 7

8 The Law of Conservation of Angular Momentum When rotations are introduced, a trampolinist who is high in the air has generated angular momentum: the product of the rate at which the athlete is rotating, known as angular velocity, and the extent to which the athlete s body resists angular motion. Resistance to angular motion is known as the moment of inertia. The law of conservation of angular momentum states that the total angular momentum of a rotating body remains constant if the net torque acting on it is zero Thompson Educational Publishing, Inc. 8

9 Assessing Functional Movement Functional movement is movement that is a product of the world we live in. Such movement places demands on our core musculature and ner vous system. Functional movement also usually involves multidirectional and multi-joint movements. Biomechanists and other movement professionals assess functional movement in order to improve not only a person s movement proficiency, or competence, but also their movement efficiency Thompson Educational Publishing, Inc. 9

10 Efficiency of Movement An efficient movement is one that uses the least amount of energy to complete a task. The tasks that humans perform vary widely, from walking, to competing in a sport, to working on an assembly line, and so on. Inefficient movements can lead to errors in performance, fatigue, injur y, or even death. Moving efficiently helps people sustain their energy output for as long as possible. Wasted energy (known as an energy leak) leads to fatigue more quickly Thompson Educational Publishing, Inc. 10

11 Maximizing Efficiency Through Practice 2015 Thompson Educational Publishing, Inc. 11

12 Disruptions in Movement Patterns Movement professionals often use information gained from movement analyses to counteract situations that disrupt the proficiency and efficiency of human movement. For example, rapid growth during adolescence can shift the location of a young person s centre of mass, which can temporarily affect balance, coordination, and performance. Disrupted movement patterns can also arise from congenital conditions such as fibular hemimelia, or the absence of fibulas in the lower limbs. Injuries such as a sprained ankle can also disrupt well-established, efficient movement patterns Thompson Educational Publishing, Inc. 12

13 Overcoming Disrupted Movement Patterns 2015 Thompson Educational Publishing, Inc. 13

14 Methods of Movement Analysis Biomechanists, physiotherapists, rehabilitation specialists, coaches, and other movement professionals spend a great deal of time assessing functional movement in a wide variety of contexts. They rely on two major methods of analysis: qualitative (non-numerical) analysis, or quantitative (numerical) analysis. Sometimes, however, analyses of human movement depend on a combination of both qualitative and quantitative assessment methods Thompson Educational Publishing, Inc. 14

15 Revisiting the Question ~ ~ ~ What are some purposes for the biomechanical analysis of functional movement? 2015 Thompson Educational Publishing, Inc. 15

16 Lesson 13.1 SUMMARY Analysis of human functional movement based on an understanding of biomechanical concepts and principles ser ves many purposes. The goals of movement analysis vary depending on the outcome. Functional movement assessment strives to improve a person s movement proficiency, or competence, as well as their movement efficiency. Biomechanists and other movement professionals use qualitative analysis, quantitative analysis, or a combination of both to counteract disruptions in the proficiency and efficiency of human movement Thompson Educational Publishing, Inc. 16

17 Lesson 13.2 QUALITATIVE AND QUANTITATIVE ANALYSIS ~ ~ ~ TOPICS COVERED IN THIS LESSON (a) Qualitative Analysis of Human Movement (b) Quantitative Analysis of Human Movement 2015 Thompson Educational Publishing, Inc. 17

18 Focussing Question ~ ~ ~ How does qualitative analysis compare with quantitative analysis in terms of purpose and methods? 2015 Thompson Educational Publishing, Inc. 18

19 Qualitative Analysis of Human Movement Qualitative analysis of human movement involves describing and analyzing movements primarily by using non-numerical methods. Qualitative analysis essentially involves observing and critiquing human movements as patterns and sequences. It ranges from a sensory observation of a movement or task to a comprehensive, structured approach involving preparation, observation, diagnosis-evaluation, and inter vention. The simplest type of qualitative analysis features verbal feedback, whether spoken or written Thompson Educational Publishing, Inc. 19

20 Purposes of Qualitative Analysis A qualitative analyst is typically interested in observing and evaluating the technique that an individual uses in executing a particular skill or performing a particular movement pattern. For example, a coach standing on the edge of a pool can tell a diver immediately whether she under-rotated, over-rotated, or remained vertical when entering the water. Similarly, physiotherapists or athletic therapists apply their knowledge of movement proficiency and efficiency to assess the quality of a client s movement pattern following an injury. Through qualitative intervention, movement professionals can offer individuals advice and guidance on how to perform better Thompson Educational Publishing, Inc. 20

21 Knowledge-Based Sensory Observations Qualitative analysis relies heavily on a movement professional s powers of observation as well as on their thorough understanding of the techniques and biomechanical principles related to a specific activity, sport, or exercise. Careful visual observation of the movement pattern and the outcome of a performance if it is sport-related (e.g., whether a pole vaulter cleared a bar), are essential parts of qualitative analysis. The observer may use other senses to gather qualitative information as well, e.g., by listening to the rhythm of a basketball player s feet during the performance of a lay-up shot Thompson Educational Publishing, Inc. 21

22 Coaching Requires Qualitative Analysis 2015 Thompson Educational Publishing, Inc. 22

23 Advantages of Qualitative Analysis Qualitative analyses offer a number of advantages: They can be conducted in many different settings. They require little or no equipment. The person performing the movement can receive immediate verbal feedback about the quality of his or her efforts. If the qualitative analyst keeps a written record of observations and repeats the analysis, the performer and the movement professional can assess improvement in performance over time Thompson Educational Publishing, Inc. 23

24 Disadvantages of Qualitative Analysis Qualitative analyses also have limitations: If the observer lacks knowledge in a particular area, the reliability and validity of the results of the analysis will be questionable. Observer bias can influence the results of the assessment. If an activity takes place at a high rate of speed a golf swing, for example or if a movement is relatively small and difficult to attempt, a qualitative approach may not work. In such cases, the movement professional may choose to incorporate quantitative methods of analysis as well Thompson Educational Publishing, Inc. 24

25 Quantitative Analysis of Human Movement Quantitative analysis of human movement uses instruments to generate numerical data to measure and quantify the movement being obser ved. For example, a coach might use a stopwatch to time runners completing a 200 m sprint. Similarly, phsiotherapists and orthopedic surgeons use a stopwatch to conduct a Timed Up and Go (TUG) Test to determine the severity of disability of a person who needs hip replacement surgery. More complex quantitative analysis might involve image-based motion analysis, automatic markertracking systems, and force or pressure plates to measure foot-strike patterns of athletes Thompson Educational Publishing, Inc. 25

26 Who Uses Quantitative Analysis? The complex mathematical models upon which quantitative analysis often depends may be of little practical use to a teacher or coach. It is mainly researchers who use quantitative movement analysis of a complex nature. For example, researchers conducted an ambitious quantitative analysis of Usain Bolt s astounding 200 m sprint at the 2009 World Championships in Berlin, Germany. The researchers used measurements that approximated conditions at the time (e.g., temperature, altitude, and Bolt s surface area) as well as data from a velocity tracking device to determine Bolt s maximum power output and other information Thompson Educational Publishing, Inc. 26

27 Quantitative Analysis in a Laboratory 2015 Thompson Educational Publishing, Inc. 27

28 Advantages of Quantitative Analysis Quantitative analyses offer the following advantages: They do not rely on an observer s immediate knowledge stored in memory but rather on the expertise of those operating the instruments used to gather and analyze data. These instruments can provide data with a high degree of accuracy and reliability, thus circumventing an obser ver s bias. Sophisticated quantitative measurement systems allow complex movements some occurring at high rates of speed or others too fine to be detected by the unaided eye to be captured for later analysis Thompson Educational Publishing, Inc. 28

29 Quantitative Analysis & Olympic Wins 2015 Thompson Educational Publishing, Inc. 29

30 Disadvantages of Quantitative Analysis Quantitative analyses can have limitations: They often require expensive equipment and software. Analysts conducting complex quantitative analyses require high levels of technical skills to operate equipment and generate and analyze data. A quantitative analysis might be restricted to a laboratory setting. Lab-based studies may not replicate the real-world conditions of a sport or activity as effectively as a field-based study. Quantitative analyses can be time-consuming to complete Thompson Educational Publishing, Inc. 30

31 Revisiting the Question ~ ~ ~ How does qualitative analysis compare with quantitative analysis in terms of purpose and methods? 2015 Thompson Educational Publishing, Inc. 31

32 Lesson 13.2 SUMMARY There are two main methods of analyzing human movement: qualitative analysis and quantitative analysis. Qualitative analysis describes movement and techniques primarily by using non-numerical information such as knowledge-based sensory observations. Quantitative analysis uses instruments to generate numerical data related to movement. Physical education teachers, coaches, athletes, physiotherapists, kinesiologists, gait analysts, and judges of artistic sports use qualitative analysis. Mainly researchers use quantitative analysis Thompson Educational Publishing, Inc. 32

33 Lesson 13.3 BIOMECHANICAL ANALYSIS PART 1 ~ ~ ~ TOPICS COVERED IN THIS LESSON (a) The Biomechanics of Walking (b) The Biomechanics of a Soccer Kick 2015 Thompson Educational Publishing, Inc. 33

34 Focussing Question ~ ~ ~ How can we analyze human movement from a biomechanical perspective? 2015 Thompson Educational Publishing, Inc. 34

35 The Biomechanical Perspective To analyze movement from a biomechanical perspective, we must simultaneously apply our understanding of the following: The various internal and external forces acting on the human body The seven principles of biomechanics The anatomical structure of the human body 2015 Thompson Educational Publishing, Inc. 35

36 Example 1: Walking The force of gravity plays a major role in our walking proficiency from toddlerhood to our senior years. Gravity works in opposition to a toddler who tries to maintain an upright position while learning to walk. To counter the effects of gravity, at least minimal leg strength is required as well as an ability to balance on one leg. Through practice, the child makes gains in neural control of musculature and in muscle strength, this increasing his or her ability to counter the effects of gravity Thompson Educational Publishing, Inc. 36

37 Walking and the Principle of Stability Learning to walk provides a good example of the principle of stability in action. To prevent a fall, a toddler takes short steps forward with feet flat and in a wide stance. This wide stance is facilitated by pointing the toes outward. The wide stance increases the width of the toddler s base of support, thus increasing the child s stability Thompson Educational Publishing, Inc. 37

38 Walking and Principle 4 Over time, a child acquires a more mature, proficient walking pattern. This more proficient pattern of walking is characterized by an increased stride length. The increased stride length allows a greater application of force (i.e., impulse) by the foot against the ground at push-off. This action, therefore, demonstrates biomechanical principle 4, the impulse-momentum relationship, which states: The greater the applied impulse, the greater the increase in velocity Thompson Educational Publishing, Inc. 38

39 Walking and Principle 5 As the child gains greater control of his or her balance, out-toeing is reduced and the base of support narrows. This narrowed base of support allows more force to be applied in a forward-backward direction. Eventually, the child will grow up and demonstrate the mature, proficient walking pattern of a young adult. This example illustrates biomechanical principle 5: Movement usually occurs in the direction opposite that of the applied force Thompson Educational Publishing, Inc. 39

40 The Effects of Aging on Walking Over time, disease, injury, and natural aging processes reduce a person s walking proficiency. Aging individuals who experience a loss of muscle mass and muscle strength may shorten their stride length or out-toe a little more in an effort to become more stable. With regular physical activity, the ability to walk with a high degree of proficiency can generally be maintained throughout the human lifespan Thompson Educational Publishing, Inc. 40

41 Example 2: Kicking a Soccer Ball Our ability to kick a ball develops rapidly between the ages of four and six, and by the age of nine the pattern is mature. There are distinctly observable biomechanical differences between a highly proficient kicker and a beginning kicker. Proficient kickers demonstrate a refined and consistent movement pattern whereas novices demonstrate a variable and inconsistent one. A successful kick is usually defined either in terms of the velocity of the ball, or the accuracy of direction of the kick, which relies on the position of the plant (non-kicking) foot and hip position at impact Thompson Educational Publishing, Inc. 41

42 Forces Involved in a Soccer Kick A thorough qualitative analysis of a free kick in soccer requires an understanding of multiple external and internal forces acting on the ball, the player, and the turf that supports them. For example, from the moment the ball leaves the toe of a soccer player, gravity acts on the mass of the ball, giving it weight and resisting its upward motion. Wind is another external force that can slow down, speed up, or push the ball sideways as it hurtles toward the goal. Pushing down on the ground with the non-kicking foot generates ground reaction force, which helps the soccer player impart force to the ball Thompson Educational Publishing, Inc. 42

43 The Effect of Ground Reaction Force If the player taking the kick is right-footed, she will need to plant her left foot on the ground as her right leg swings and makes contact with the ball. If her plant foot slides as she attempts to make the kick, she will generate little ground reaction force and the resulting kick will be weak. If the plant foot stays in contact with the ground, it will generate a strong ground reaction force and the resulting force will be strong. To prevent her foot from sliding, the player s shoes have cleats to increase friction Thompson Educational Publishing, Inc. 43

44 A Successful Soccer Kick 2015 Thompson Educational Publishing, Inc. 44

45 Analyzing a Soccer Kick Qualitatively A soccer kick illustrates several other biomechanical concepts and principles: The player s running approach toward the ball creates momentum and permits a long angular swing of her kicking leg toward the ball. The kicking leg acts as a third class lever in propelling the ball forward toward the goal cage. Maximum velocity is imparted to the ball as a result of sequenced movements, beginning with flexion at the hip joint, followed by extension at the knee, and then dorsiflexion at the ankle. This demonstrates biomechanical principle Thompson Educational Publishing, Inc. 45

46 Analyzing a Soccer Kick Qualitatively A successful soccer kick also demonstrates biomechanical principles 1 and 4: As the kicking leg swings to kick the ball, the player moves her arms in an effort to keep her centre of mass positioned over the supporting leg. When the kicking foot contacts the ball, a force is applied to the ball over a period of time. The application of this pushing force over time or impulse causes the ball to move. If the foot makes contact with the ball such that the applied force does not act through the ball s centre of mass, the ball will spin. This spinning action allows the ball to bend as it moves toward the goal cage Thompson Educational Publishing, Inc. 46

47 Revisiting the Question ~ ~ ~ How can we analyze human movement from a biomechanical perspective? 2015 Thompson Educational Publishing, Inc. 47

48 Lesson 13.3 SUMMARY All human movement including everyday actions such as walking as well as sports-related actions such as kicking a soccer ball can be analyzed qualitatively from a biomechanical perspective. Qualitative movement analysis involves simultaneous application of knowledge of internal and external forces acting on the human body, the principles of biomechanics, and human anatomy. Changes in walking patterns from toddlerhood to our senior years demonstrate the effects of gravity and biomechanical principles 1, 4, and 5. A successful soccer kick demonstrates biomechanical principles 1, 3, and Thompson Educational Publishing, Inc. 48

49 Lesson 13.4 BIOMECHANICAL ANALYSIS PART 2 ~ ~ ~ TOPICS COVERED IN THIS LESSON (a) The Biomechanics of a Wrist Shot (b) Computerized Motion Analysis 2015 Thompson Educational Publishing, Inc. 49

50 Focussing Question ~ ~ ~ In what ways can we conduct a biomechanical breakdown of human movement patterns? 2015 Thompson Educational Publishing, Inc. 50

51 Example 3: Taking a Wrist Shot In the individual skills competition in floor hockey, shoot for accuracy is one of five different tasks that make up the event. Athletes shoot on goal from a distance of 5 m. The goal cage is divided into six scoring areas, with the highest scores allotted to shots that enter the upper right- and left-hand corners. Players have five opportunities to propel a 20 cm diameter felt ring, or puck, at the net to score points. Players attempt to elevate the puck using a wrist shot, applying the same biomechanical principles as those used for a wrist shot in ice hockey Thompson Educational Publishing, Inc. 51

52 Using the Stick as a Lever From a qualitative perspective, propelling the puck requires the athlete to use his or her stick as a lever. The pull of the top hand on the stick provides the effort force. The puck represents the resistance (or load) to be moved. The fulcrum (or axis of rotation) exists at the location of the player s bottom hand, which grips the stick about mid-way down the shaft Thompson Educational Publishing, Inc. 52

53 Ground Reaction Force and Principle 1 As the player uses his or her arms along with the stick as a lever, the player is also stepping into the shot. He pushes backward with his back foot to create a ground reaction force. This ground reaction force directs his body and the puck in a forward direction. His front foot, in turn, plants and his arms swing around his body, in an effort to keep his centre of mass over this new base of support and to maintain his balance (biomechanical principle 1) Thompson Educational Publishing, Inc. 53

54 Friction, Gravity, and Momentum The forces of friction and gravity act on the puck, and the shooter imparts momentum to it. As the puck slides across the playing surface, a frictional force arises between the puck and the surface, opposing the puck s forward motion. The force of gravity also acts on the puck from the moment it leaves the player s stick. Whether or not the puck enters the goal cage in the air or along the ground depends on the angle at which it leaves the stick, as well as the amount of momentum that is imparted to the puck by the shooter Thompson Educational Publishing, Inc. 54

55 The Impulse-Momentum Relationship The shooter can increase the amount of momentum and the velocity imparted to the puck. The player can accomplish this by increasing the amount of impulse, or the time over which a pushing force is applied to the puck. Impulse is increased by starting the shot from a position behind the body, stepping into the shot, and applying a force as the stick moves forward until the point of release. These actions demonstrate biomechanical principle 4 (the impulse-momentum relationship) Thompson Educational Publishing, Inc. 55

56 Maximizing Force A wrist shot in floor hockey or ice hockey also demonstrates biomechanical principle 2. The amount of force applied to the puck is increased by the use of leg drive, and by sequencing the use of all the muscles and joints in the arm. The wrist shot relies on the sequenced use of the muscles and joints of the upper arm followed by those in the forearm, finishing with a rapid extension of the wrist Thompson Educational Publishing, Inc. 56

57 Example 4: Computerized Motion Analysis For decades now, motion capture has played an important role in biomechanical assessment and analysis. Motion capture is the process of videorecording the movements of objects or people. Motion capture is used in sports and in military, entertainment, robotics, and medical applications. In the creation of films and video games, the term refers to recording the actions of human actors, and using that information to animate digital character models in 2D or 3D computer animation. In the world of filmmaking, motion capture is often referred to as performance capture Thompson Educational Publishing, Inc. 57

58 Motion-Capture Systems For many years, sport scientists have used computerized motion-capture systems high-speed digital video cameras connected to powerful computers to evaluate the performance of elite athletes. Increasingly, teachers, coaches, and trainers are using this technology to conduct a biomechanical breakdown of the movement patterns of students and amateur athletes, too. This type of analysis can slow down activities such as running, jumping, throwing, and striking in order to pinpoint energy leaks in the body s movement patterns that can reduce an athlete s power and efficiency Thompson Educational Publishing, Inc. 58

59 Computerized Motion Analysis & Training 2015 Thompson Educational Publishing, Inc. 59

60 Analyzing a Jump Shot in Basketball The data captured by computerized motion analysis can break down a jump shot in basketball. The jump shot which usually takes about one second is broken down into nine separate actions, or phases. Viewing each phase separately can reveal where an athlete is making one or more errors in executing a shot. When the errors are corrected, the player s shooting performance will improve Thompson Educational Publishing, Inc. 60

61 Coach s Eye Coach s Eye is a multimedia application used in computerized motion analysis. This program is popular with physical education teachers because it allows instant feedback for students. It can record a student performing a skill and then play it backwards, in slow motion, or frame by frame. The person using the program can also draw on screen or record a playback with verbal comments Thompson Educational Publishing, Inc. 61

62 Ubersense Ubersense is used by countless teachers, students, coaches and athletes to improve technique and performance in almost ever y sport or activity. Ubersense is a free mobile app that lets users record movements in high definition. The movements can be analyzed using slow motion and drawings. Users can also watch drills from professional coaches and share videos Thompson Educational Publishing, Inc. 62

63 Revisiting the Question ~ ~ ~ In what ways can we conduct a biomechanical breakdown of human movement patterns? 2015 Thompson Educational Publishing, Inc. 63

64 Lesson 13.4 SUMMARY Biomechanical movement analysis often relies on an analyst s powers of sensory obser vation. Additionally, computerized motion analysis is being used to break down human movement patterns in order to help correct errors. Taking a wrist shot in floor hockey demonstrates a number of biomechanical concepts (e.g., the stick is used as a lever) as well as principles 1, 2, and 4. Increasingly, teachers, coaches, and trainers are using motion-capture systems such as Coach s Eye and Ubersense to conduct a biomechanical breakdown of human movement patterns Thompson Educational Publishing, Inc. 64