Unit4_Biomechanics Introduction for Engineers

Biomechanics introduction

1. Chapter-4 Biomechanics

2. Course Outcome At the end of the unit, you would be able to understand Key mechanical concepts 9 fundamentals of biomechanics Biomechanics of passive muscle tendon unit Biomechanics of bone Biomechanics of ligaments

3. What is biomechanics Video 0

4. Necessity 5 4 3 2 1 Highly interdisciplinary Treat injuries Replicate human motion Study human behaviour Posture and form

5. INtroduction Video 1

6. Why study Biomechanics Highly interdisciplinary field with people from mechanical, computer science, electronics all come together Helps to understand human movements Useful for treating sports injury (physiotherapy) Useful to know the right postures when doing exercises to remove stress and strain Useful to replicate human motion in AI and robotics Study human behavior by studying their movement (gait analysis) Useful if one wants to work on material sciences and human implants Work in collaboration with other departments for medical device design

7. Application biomechanics Video 1.1 games Video 1.2 Sports Video 1.3 Movies

8. Why Study Biomechanics? The purpose of studying Biomechanics is; To understand the forces acting on the human body. To manipulate these forces in treatment procedures so that human performance may be improved and further injury may be prevented. Better understanding of both joint function and dysfunction To understand how the musculoskeletal system functions. Useful in patient evaluations and treatments. Important for clinicians such as orthopaedic surgeons and physical and occupational therapists

9. BIOMECHANICS Kinesiology is the scholarly study of human movement. Kinesiology = biomechanics + anatomy+ physiology+neuroscience “Biomechanics has been defined as the study of the movement of living things using the science of mechanics ( Hatze , 1974)”. Biomechanics is the science of movement of a living body, including how muscles, bones, tendons, and ligaments work together to produce movement. Involves the principles of anatomy and physics in the descriptions and analysis of movement. How system and structures react to external force

10. FOUNDATIONS OF MOVEMENT To move, the human body goes through a complex series of interactions that involve different body systems. Communication between the muscular, skeletal, and nervous systems all come into play. Skeletal system : The human skeleton is the framework that supports the human body. Without bones, you could not stand, sit, or walk. Muscular system : Muscles are connected to bones. When a muscle contracts, it often produces movement around a joint and also supports the body and increases stability. Nervous system : Every movement you make is controlled by the nervous system, or brain-body connection.

11. BIOMECHANICS & NEWTON’S LAWS OF MOTION Law of inertia: An object at rest will stay at rest and an object in motion will stay in constant linear motion unless acted on by an outside force. If a ball is rolling, it will keep rolling forever unless something stops it. In the same way, if a ball is at rest, it will stay at rest until a force pushes it to move. Law of acceleration: The acceleration of an object is directly proportional to the force acting on it and inversely proportional to the mass of the object. As the force acting upon an object increases, the acceleration of the object also increases. As the mass of an object increases, the acceleration of the object decreases for a fixed force. Law of action and reaction : For every action there is an equal and opposite reaction. When one object exerts a force on a second object, the second object reacts by exerting an equal force in the opposite direction on the first object. For example, when you walk, your body pushes down on the ground to move yourself forward. The ground pushes back against you with the same magnitude of force, propelling you forward.

12. NINE FUNDAMENTALS OF BIOMECHANICS Biomechanists measure all kinds of linear and angular mechanical variables to document and find the causes of human motion. There are nine principles of biomechanics constitute the minimum number or core principles that can be applied to all human movements. These are used to develop generic biomechanical principles for all human movements. They provide a simple paradigm or structure to apply biomechanical knowledge. Each can be directly linked to the concepts and laws of biomechanics.

13. Human to outside world Video 1.4

14. B ( alance ) I ( nertia ) F ( orce -Motion) F ( orce -Time) C R O S S ( oordination ( ange ) ( ptimal ) ( egmental ) ( pin) Continuum) projection interaction

15. 1. Balance The degree of control over stability/ instability. Balance is a person's ability to, control their body position relative to some base of support. Stability and mobility of body postures are inversely related, and several biomechanical factors are involved in manipulating a person's stability and mobility. To increase stability increase base of support, lower center of gravity increase mass of the body. Line of gravity should fall in the middle of your base of support for max stability.

16. Factors that affect Balance Mass (more mass, more is the force required to unstabilize it) Base Of Support- larger base of support is more stable. C.O.G- Closer the COG to the BOS, more is the stability Line of gravity- If it crosses through BOS, more stable

17. Balance Video 2 COG Video 2.1 Fossbury jump

18. 2. Inertia Inertia can be defined as the property of all objects to resist changes in their state of motion (either reset or in motion). Defined by Newton's first law of motion. As we have linear motion and angular motion, we have linear and angular measures of inertia. The heavier the mass, more force it requires to be moved. Moment of Inertia refers to the resistance of rotational motion.

19. 3. Force-Motion Force are required to change the state of motion. Unbalanced forces are acting on our bodies when we create or modify movement. An important thing to notice in this principle is the sequence of events. Forces must act first, before changes in motion can occur. Relates to newtons 3 laws. Example Standing still- forces acting on a person are equal and because of this there is no movement.

20.  2. Force-Time Substantial changes in motion do not instantly occur but are created over time, which leads to the principle of Force–Time. Impulse=Force X Time. The greater the time of which force is applied the greater the resulting motion. The impulse–momentum relationship, the original language of Newton’s second law, is the mathematical explanation of this important principle. Example of Force-Time Using the sweep shot in hockey. More force and time is applied giving it much more power then a hit.

21. 4. Coordination Continuum Organization between simultaneous sequential actions. Involves sequencing and timing bodies actions to create movement. High levels of force are effectively created through simultaneous segmental movements while lower force and high speed movements require a sequential pattern of movement to be effective. The continuum contains simultaneous at one end and sequential at another. Most actions fall somewhere in between.

22. 6. Range Of Motion Body motion used in a movement Relates to the type of motion ( linear or angular) of body segments used to create movement. Reduced R.O.M is best for low force and high accuracy actions while increased R.O.M is required for speed and force production. Example of Range Of Motion Reduced R.O.M= Throwing a dart. Increased R.O.M= Throwing a javelin

23. 8. Optimal Projection Impact of release conditions that optimize performance. There is an optimal angle of projection to achieve a specific goal. Biomechanical research shows that optimal angles of projection provide the right compromise between vertical velocity and horizontal velocity within the typical conditions encountered in many sports. Maximum speed/distance of an optimal angle=45 degrees . Parameters that needs to be considered: Velocity (horizontal and vertical) Angle of release Height of release

24. projectile Matlab

25. 5. Segmental Interactions The forces acting in a system of linked rigid bodies can be transferred through the links and joints . Using your body parts in order to create maximum power in a shot. Begins with the largest, slowest, strongest segments and works through to the slowest and fastest segments. Example of Segmental Interactions Golf shot. Tennis shot

26. 9. Spin Projectile rotation to stabilize flight and adjust trajectory (particularly sport balls). Spin will cause an object to lift. Lift will cause a curve and counter the affects of gravity. Example of Spin A tennis player putting a top spin on a ball to make it drop quicker. A volleyball player performing a jump serve should strike above the center of the ball to impart topspin to the ball.

27. spin Video 3 cricket Video 3.1 football

28. Muscular Anatomy Muscular system consists of three muscle types: cardiac, smooth, and skeletal. Skeletal muscle most abundant tissue in the human body (40-45% of total body weight). Human body has more than 430 pairs of skeletal muscle; most vigorous movement produced by 80 pairs. Skeletal muscles provide strength and protection for the skeleton, enable bones to move, provide the maintenance of body posture against gravity. Skeletal muscles perform both dynamic and static work Dynamic: locomotion & positioning of segments Static: maintains body posture

29. Types of Muscles In the body, there are three types of muscle: skeletal (striated), smooth, and cardiac. Skeletal Muscle Skeletal muscle, attached to bones, is responsible for skeletal movements. These muscles are under conscious, or voluntary, control . Smooth Muscle Smooth muscle, found in the walls of the hollow internal organs such as blood vessels, the gastrointestinal tract, bladder, and uterus, is under control of the autonomic nervous system. Smooth muscle cannot be controlled consciously and thus acts involuntarily. The non-striated (smooth) muscle cell is spindle-shaped and has one central nucleus. Smooth muscle contracts slowly and rhythmically. Cardiac Muscle Cardiac muscle, found in the walls of the heart, is also under control of the autonomic nervous system. The cardiac muscle cell has one central nucleus, like smooth muscle, but it also is striated, like skeletal muscle. The cardiac muscle cell is rectangular in shape. The contraction of cardiac muscle is involuntary, strong, and rhythmical.

30. Muscle Anatomy Skeletal muscles Covered by protective layer of connective tissue – epimysium (protects from friction) Muscles made of thousands of bundles called muscle fibre bundles/fascicles Each bundle covered by another connective tissue perimysium Each bundle contains thousands of muscle fibres, which is covered by endomysium Endomysium is connected with blood vessels and ion exchange channels.Mostly made up of collagen. Allows automatic gliding during muscle contraction Each muscle fibre made of myofibrils which contains repeating units of sarcomeres Each sarcomere contains thick (myosin) and thin (actin) filaments.

31. Review of Muscle Structure Muscle fibers are some of the largest cells in the body and are long cylindrical structures with multiple nuclei. Besides many nuclei there are hundreds to thousands of smaller protein filaments called myofibrils in every muscle fiber. These small sections of a myofibril between two Z lines (thin dark band) are called sarcomeres . Sarcomeres are the basic contractile structures of muscle . These contain the sarcolemma

32. Molecular structure of Myofibril Myosin composed of individual molecules each has a globular head and tail Head binds with actin and moves along with it Cross-bridge: actin & myosin overlap (A band) Actin has double helix; two strands of beads spiraling around each other troponin & tropomysin regulate making and breaking contact between actin & myosin During resting stage, Tropomyosin covers actin’s active sites so that actin-myosin interaction does not take place. When impulses reach the muscle sarcolemma, Ca2+ channels open and Ca2+ ions interact with tropomyosin and allows the formation of actin-myosin cross links. Movement of myosin heads over actin filaments based on ATP activity causes muscle contraction.

33. ATP –ADP CYCLE IN MUSCLE MOTION

34. MUSCLE CONTRACTION THEORY Video 4 Video 4.1

35. Muscle action Muscle forces are the main internal motors and brakes for human movement. Gravity and other external forces can be used to help us move. Torques created by skeletal muscles that are coordinated with the torques from external forces to obtain the human motion of interest. The activation of skeletal muscle has traditionally been called contraction or muscle action . Muscle contraction involves the activation of muscle fibres and force generation that facilitates body movements and posture maintenance. “ Muscle action is the neuromuscular activation of muscles that contributes to movement or stabilization of the musculoskeletal system.”

36. Muscle action 4 major actions – Isometric – muscle tension increases but muscle length remains same Isotonic – fibre length changes but the tension remains the same Concentric – muscle length shortens. Requires more energy investment. Eccentric – muscle length increases. Greater forces at lower costs. Response to a greater opposing force Isokinetic – velocity of muscle contraction remains same but length changes. Can be concentric or eccentric. * Low-velocity exercises generally increase muscle strength, while high-velocity exercises are mainly used for the recovery of muscle endurance following an injury

37. Muscle action Video 5

38. Types of Muscle Contraction Type of Contraction Definition Work Concentric Force of muscle contraction  resistance Positive work; muscle moment and angular velocity of joint in same direction Eccentric Force of muscle contraction  resistance Negative work; muscle moment and angular velocity of joint in opposite direction Isokinetic Force of muscle contraction = resistance; constant angular velocity; special case is isometric contraction Positive work; muscle moment and angular velocity of joint in same direction Isometric Force of muscle contraction  resistance; series elastic component stretch = shortening of contractile element (few to 7% of resting length of muscle) No mechanical work; physiological work

39. Muscle action Tension in the muscles in the main stimulus to develop muscles –size and strength Result from both active and passive components of muscle tension. Passive tension- recoil tension/force. No energy Force that comes with the elongation of the connective tissue components of the muscle tendon unit Ex. Tension felt in the muscles during stretching exercise is the passive resistance to the elongation of the stretch. Represented by the Force-Length relationship of the muscles. Active tension- tension/force when muscle is stimulated to contract. Involves ATP Forces created between actin and myosin fibres in the sarcomeres Force created by the contractile proteins using ATP Represented by the Force-velocity relationship

40. Muscle action Active tension Passive tension https://www.youtube.com/watch?v=eTs9EnlbFew Concentric contraction F increases, V decreases Eccentric contraction F increases, V increases

41. Force length relationship Video 6

42. Hill Muscle Model One of the most widely used mechanical models of muscle that takes into account both the active and passive components of muscle tension is the three-component model developed by A. V. Hill in 1938 : Hill model The Hill model of muscle describes the active and passive tension created by the muscle tendon unit (MTU). Computational models of muscles serve as important tools to understand the musculoskeletal physiology and biomechanics. Such models have been widely implemented in a variety of simulation platforms and incorporate varying degrees of physiological details.

43. Hills Model The Hill muscle model has two elements in series and one element in parallel. The contractile component (CC) represents the active tension of skeletal muscle. Parallel elastic component (PEC) and series elastic component (SEC) represent two key sources of passive tension in muscle. The Hill muscle model has been the dominant theoretical model for understanding muscle mechanics. Also used in biomechanical computer models employed to simulate human movement.

44. Generalizations about the mechanical behavior of muscle are based on Hills model. Elasticity (connective tissue) in the production of active muscle tension modeled by the series elastic component. The source of this series elasticity is likely a mixture of the actin/myosin filaments, cross bridge stiffness, sarcomere non-uniformity, and other sarcomere connective tissue components. Second, the passive tension of relaxed muscle that is easily felt in stretching exercises or in passive insufficiency affects motion at the extremes of joint range of motion. The “p” in the parallel elastic component that forms the primary source of passive tension in the Hill muscle model . This third point can be generalized beyond the simple Hill muscle model, that is focused on the complex transmission of force within the connective tissue components of muscle. Muscles may not create equal forces at their attachments because of force transmitted to extra muscular connective tissues. Stretch and recoil of elastic structures are an integral part of all muscle actions. Hills Model

45. Hills Model ( v+b )( F+a )= b( F O +a ) Where, F is the tension in the muscle V is the velocity of contraction Fo is the maximum isometric tension a is the coefficient of shortening heat b= a.v o / F o Where v o is the maximum velocity at F=0

46. MECHANICS OF THE PASSIVE MUSCLE–TENDON UNIT (MTU) The mechanical response of the MTU to passive stretching is viscoelastic . Viscoelastic means that the stress and strain in a material are dependent on the rate of loading . So the response of the tissue depends on the time or rate of stretch. At a high rate of passive stretch, the MTU is stiffer than when it is slowly stretched. This is the primary reason why slow, static stretching exercises are preferred over ballistic stretching techniques. A slow stretch results in less passive tension in the muscle for a given amount of elongation compared to a faster stretch.

47. Muscle Tendon Unit Video 7 Stretching

48. Tendon Tendon is the connective tissue that links muscle to bone and strongly affects how muscles are used or injured in movement. Tendon is a well-vascularized tissue whose mechanical response is primarily related to the protein fiber collagen. The parallel arrangement of collagen fibers in tendon and cross-links between fibers makes tendon about three times stronger in tension than muscle.

49. Tendon Video 8.1 Complete muscle building

50. Tendon The ultimate strength of tendon is usually about 100 MPa (megapascals). Even though the diameter of tendons is often smaller than the associated muscle belly, their great tensile strength makes tendon rupture injuries rare. Acute overloading of the MTU usually results in strains (sports medicine term for overstretched muscle, not mechanical strain) and failures at the muscle tendon junction or the tendon/bone interface.

51. tendon Application Video 8

52. MECHANICS OF THE PASSIVE MUSCLE–TENDON UNIT (MTU) Tendon acts as a series viscoelastic component in the muscle tendon complex Tendon stiffness (K) can effect the relationship between force and velocity in muscle

53. Significance of Tendon In creating movement, a long tendon can act as an efficient spring in fast bouncing movements. A muscle with a short tendon transfers force to the bone more quickly because there is less slack to be taken out of the tendon. The intrinsic muscles of the hand are well suited to the fast finger movements of a violinist because of their short tendons. The Achilles tendon provides shock absorption and compliance to smooth out the forces of the large calf muscle group.

54. tendon Tendonities Video 9 Tendon Rupture Video 9.1, 9.2

55. Biomechanics of bone

56. Purpose of the skeletal system To protect internal organs, provide rigid kinematic links and muscle attachment sites, and facilitate muscle action and body movement. Bone has unique structure and mechanical properties that allow it to carry out these roles. Bones are living tissues with blood supplies, made of a high percentage of water (25% of bone mass) Among the body's hardest structures; only dentin and enamel in the teeth are harder. This highly vascular tissue has an excellent capacity for self-repair and can alter its properties and configuration in response to changes in mechanical demand. Bones protect the vital organs and help to support the human body.

57. Bone Composition and Structure Normal human bone is composed of: Mineral or inorganic portion: It consists primarily of calcium and phosphate, mainly in the form of small crystals resembling synthetic hydroxyapatite crystals with the composition Ca 10 (PO 4 ) 6 (OH) 2. accounts for 60 to 70% of its dry weight. Water: 5-8%. Organic matrix: remainder of the tissue

58. Bone tissue Bone tissue, or osseous tissue, - a type of connective tissue used in forming bones. Bone is composed mainly of collagen, or ossein, fibers, and bone cells called osteocytes. There are two types of bone tissue, referred to as cortical bone and cancellous bone.

59. Longitudinal section of human femur. The direction of principal stresses are shown in the scheme on the right

60. Compact bone or (Cortical bone). The hard outer layer of bones is composed of compact bone tissue, so-called due to its minimal gaps and spaces. This tissue gives bones their smooth, white, and solid appearance, and accounts for 80% of the total bone mass of an adult skeleton. Trabecular bone It is an open cell porous network also called cancellous or spongy bone filling the interior of the organ. It is composed of a network of rod- and plate-like elements that make the overall organ lighter and allowing room for blood vessels and marrow

61. Types of bones There are several types of bones in the body: short bones, such as those in the wrist; flat bones, such as the shoulder blade or scapula, irregular bones, such as the malleus inside the ear; and Long Bone- eg : thigh bone

62. Long bones (femur)

63. Short bones (wrist, ankle)

64. Flat bones (skull, scapula)

65. Irregular bones (vertebrae)

66. Biomechanics Aspect of Bone Bone tissue is viscoelastic — it has stress-strain characteristics that are dependent upon the applied strain rate. In other words, a specimen of bone tissue that is exposed to very rapid loading will absorb more energy than a specimen that is loaded more slowly. Bone tissue is also anisotropic (its modulus is dependent upon the direction of loading) means the bone tissue can bear higher loads in the longitudinal direction. Therefore, bone tissue is both anisotropic and viscoelastic. Because of these characteristics one must specify the strain rate and the direction of applied loading when discussing bone material behavior.

67. Biomechanics Aspect of Bone The ability of bone to resist an applied load before failure or fracture is dependent on multiple factors. Age, disease, hormone levels, too little load, too much load, or even the direction in which a load is applied can all influence the biomechanical properties of bone. In particular, the potential of the bone to resist fracture is affected by these physiologic and mechanical sources. A thorough understanding of structural and mechanical properties relationship allows one to consider how the aforementioned factors change the ability of bone to withstand an applied load.

68. Biomechanics Aspect of Bone Unlike muscle, the primary loads experienced by most bones are compressive. The mechanical response of bone to compression, tension, and other complex loads depends on the complex structure of bones. Immobilization or inactivity will result in dramatic decreases in bone density, stiffness, and mechanical strength.

69. Biomechanics Aspect of Bone tissue A German scientist is credited with the discovery that bones remodel (lay down greater mineral deposits) according to the mechanical stress in that area of bone. The laying down of bone where it is stressed and reabsorption of bone in the absence of stress is called Wolff's Law . “Bone in a healthy person or animal will adapt to the loads under which it is placed”

70. Biomechanics of Ligaments

71. Ligaments are soft collagenous tissues that connects bone to bone. Plays a important role in maintaining the stability of a joint and also hold joints together. It is also capable to restrict joint motion. Shares similar structure as that of tendon. Ligament microstructure can be visualized using polarized light that reveals collagen bundles aligned along the long axis of the ligament and displaying an underlying "waviness" or crimp along the length. Crimp is thought to play a biomechanical role, possibly relating to the ligaments loading state with increased loading likely resulting in some areas of the ligament uncrimping, allowing the ligament to elongate without sustaining damage

72. Structure of Ligaments Ligaments are dense connective tissues that contain collagen, elastin, proteoglycans, water, and fibroblasts. Approximately 70 to 80 percent of the dry weight of ligament consists of Type I collagen, which is a fibrous protein. The collagen fibril is the basic load bearing unit of ligament. The fibril consists of bundles of microfibrils held together by biochemical bonds (called cross-links) between the collagen molecules. Because these cross-links bind the microfibrils together, the number and state of the cross-links are thought to have a significant effect on the strength of the connective tissue.

73. Schematic diagram of ligament

74. BASIS FOR COMPARISON TENDONS LIGAMENTS Definition Tendon connects muscles to bone, and are present at the end of skeletal muscles. These are the fibrous connective tissue non-elastic. Ligaments connect one bone to another bone and so are found in joints. These are also the kind of connective tissue which is stronger and flexible and helps in movements of the bones. Nature Tendons are inelastic and tough. Ligaments are elastic and strong. Fibres Fibres are present as compact parallel bundles. Fibres are compactly packed and not arranged in parallel bundles. Fibroblasts In tendon, fibroblasts lie in continuous rows. In ligaments, fibroblasts are scattered. Formed of Tendons are made of white fibrous connective tissue. Ligaments are made of yellow fibrous connective tissue. It joins Tendons connect end of the muscles to any place of the bone. It connects bones to bones at a joints. Classification No classification. They are divided into three categories-peritoneal ligaments, fetal remnant ligaments, and articular ligaments. Ligaments Vs Tendon

75. Biomechanical aspect of Ligaments Ligaments are passive collagenous structures that act primarily as tensile restraints to control the distance between their attachment points. Ligaments normally traverse joints, and so they act to control the relative separation of the bones that they are attached to. The ligaments control the patterns of movement, or kinematics, of joints, as well as ensuring the stability of joints. In addition to this simple mechanical description of the role of ligaments, they provide more subtle control of joint motion and stability via proprioceptive feedback to the muscles.

76. Biomechanical aspect of Ligaments Ligaments are viscoelastic structures with unique mechanical properties. The ligaments are pliant and flexible. It allows natural movement of the bones to which they attach, but are strong and inextensible so as to offer suitable resistance to applied forces. Sustain chiefly tensile loads during normal and excessive loading. When injury happens, the degree of damage is related to the rate of loading as well as the amount of load.

77. Biomechanical aspect of Ligaments Ligaments are often evaluated by using mounted specimens such as a bone-ligament-bone specimen. However , recent advances have allowed for some instrumentation to be used in the measurement of in situ forces in humans. These include the use of buckle transducers, instrumentation at insertion sites, magnetic resonance imaging, kinematic linkage measurements, and implantable transducers.

78. Stress-Strain Property of Ligaments When a tensile force is applied to the ligament at its resting length, the tissue stretches. Force-length curves can be normalized to subtract out the effects of geometry. Thus, force can be normalized by dividing by the cross-sectional area of a tissue, while length can be normalized by dividing by the initial length of the tendon or ligament. The resulting stress-strain curve displays three characteristic regions: the toe region, the linear region, and the failure region.

79. If one neglects viscoelastic behavior, a typical stress strain curve for ligaments and tendons can be drawn as:

80. Toe region: As the load increases so does the recruitment of collagen fibres causing them to ‘uncrimp’. This occurs when collagen is stretched to approximately 2% of its original length and returns to normal length when the force is removed, thus it is within its physiological range. It is characterized by relatively low stiffness. There is a non-linear relationship on the stress-strain curve at this stage.

81. Linear region (Elastic phase): As the collagen fibrils become gradually uncrimped, the fibril itself is being stretched. There now becomes a linear relationship between deformation and load, as the tissue becomes relatively stiffer. This occurs when collagen is stretched to 2-4% of its original length and returns to its original geometric shape. The tissue is said to be elastic.

82. Yield and Failure region (Plastic phase): The continued increase in load past 4% causes micro failure to the fibrils and damage to cross-links. It results in a plateau effect on the curve: this point represents the ultimate tensile strength of the tendon and is termed the ‘yield point’. The yielding of fibres occurs when the deformation is approximately 4-10% of the resting length. Stiffness is reduced and the fibrils do not return to normal length on release, the tissue then becomes ‘viscous’. This is known as ‘plastic’ deformation.

83. Finally, complete failure occurs as the ligament/tendon ruptures. Obviously this is a non-physiological range and there would be an inability to support load or function. Collagen demonstrates various mechanical and physical properties in response to load and deformation to allow it to withstand high tensile stresses. The point between the elastic and plastic region is where gross integrity is disrupted.

84. Factors That Affect the Biomechanical Properties of Ligaments Numerous factors affect the biomechanical properties of tendons and ligaments. The most common are : Aging, Pregnancy, Mobilization and immobilization, Diabetes mellitus, connective tissue disorders, renal disease etc. Pharmacologic agents (steroids, nonsteroidal Anti-inflammatory drugs or NSAIDs).

85. Video tutorial https://www.youtube.com/watch?v=U7PE736mRVk https://www.youtube.com/watch?v=LaIVBd_wJ_M