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This 15 page Class Notes was uploaded by Ticynn London on Monday February 22, 2016. The Class Notes belongs to EXSC 322 at Old Dominion University taught by Phil Sabatini in Spring 2016. Since its upload, it has received 56 views. For similar materials see Anatomical Kinesiology in Physical Education at Old Dominion University.
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Date Created: 02/22/16
Skeleton Consideration A bone is a dynamic living tissue that is continually being modeled and remodeled by the forces acting on it. What are the functions of bone? 1. provides a system of levers that can be moved by forces from muscles 2. provides a skeletal framework that supports and protects other body tissue Consist of Bones, cartilage, ligaments, and joints It is 20% of total body weight It is influenced by nutrition, physical activity, and postural habits Function 1: Levers A simple machine that magnifies the force and/or speed of movement Skeletal system provides the levers and axes about which muscle generates movement Function: Support Shape: Frame to keep body supported Movement: Transfers forces Protection: Internal organs Bone Tissue Has 25–30% water (by weight) Has 60–70% minerals and collagen Viscoelastic: Both Viscous and Elastic Properties affected by deformation rate. Composition of Bone Major building blocks of bone Calcium carbonate & calcium phosphate: provide stiffness and compressive strength Collagen: provide flexibility and tensile strength Water: Important to bone strength. Transports nutrients and waste products Composition of Bone Tissue As much as a half a gram of calcium may enter or leave the adult skeleton every day, and humans recycle 57% of their bone mass every week. Osteoclasts are the cells that break down bone and convert calcium salts into a soluble form that passes easily into the blood. Osteoblasts produce the organic fibers on which the calcium salts are deposited. Cortical Bone Trabecular Bone Also known as “spongy” bone Also known as “compact” bone It has high porosity 30-90% non-mineralized tissue It has low porosity with 5-30% non-mineralized tissue that Short Bones:more straFlatLBongeBs:ones: can withstand greater stress before fracturing but less strain Cancellous (Trabecular) bone isdarlyiwororofns interior to cortical bone and isscuslar skeleton Cortical Bone – compact bone found in the ends of long has porosity less that 15%. absorbers Provideualyeiaerxtsmoities Small changes in porosity can bones with porosity gmuscle and ligament lead to significant changes in Usually articulatend attacLarensttsbones in body the stiffness and strength of stiff than cortical bone. with more than bone. one bone Has aEx:hudmenusthiaiius, shapuelna, femur, tibia, Ex: carpals and fibula, etc. tarsals Ex: ribs, ilium, sternum, Types of Bones Structure of Long Bones Epiphysis: Metaphysis: Diaphysis: head at each end area where fusion of shaft of the bone the head and shaft occur Made of compact Wider than shaft bone Wide part of shaft Epiphyseal plate- Function- gives where bone growth Made up of strength occurs trabecular bone Function- supports the epiphysis Types of Bone Sesamoid bones: Irregular Bones: Increase the angle of insertion of a Specialized functions muscle (i.e., increase the moment arm of a do not fit in any other muscle) category – Mixed shapes Protect tendon from excessive wear Modifying pressure Ex: skull, pelvis, and Reduce friction vertebrae Alter the direction of pull of a muscle Ex: patella, base of 1 metatarsal Bone Growth Ossification: Formation of bone by the activity of osteoblasts and osteoclasts and the addition of minerals and salts Osteoblast: Cells that form bone increase bone mass Take minerals from the blood and deposit them in the bone Osteoclasts: Cells that eat away (reabsorb) old bone Decrease bone mass Longitudinal Growth: Growth ceases after the closure of the epiphyseal plates Epiphyseal plates expand, forming new cells, and increasing length of the bond 1825 years old Circumferential Growth: Osteoblast and osteoclast activity Continues throughout the lifespan Most rapid growth occurring prior to adulthood Wolff’s Law Bone strength increases and decreases as the functional forces on the bone increase and decrease bones adapt to loads loading ↑: bone will remodel to become stronger loading ↓: resorption occurs and bone weakens osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood. Osteoporosis Bone resorption exceeds bone deposits Decrease in bone mineral mass Loss of bone density – Results in a loss of stiffness Loss of trabecular integrity – Results in a weakening of the bone Increased incidence of fracture Cause is multifactorial – Hormonal factors – Nutritional imbalances – Lack of exercise Stress: force applied to deform a structure Stress = force/area Strain: deformation resulting from stress Strain = (change in length)/(resting length) StressStrain Curve • Elastic modulus Stiffness of a material • Yield point – Up to yield point, structure is in its elastic region and will return with no damage – Past the yield point is the structure’s plastic region • Failure – If the applied force continues past the plastic region, the tissue Elastic Viscoelastic will eventually fail. Linear relationship exists Non-linear or viscous between stress and properties in Types of strain combination with linear Materials elastic properties. When the applied force deforms the material, The combination of the amount of these properties results deformation is the same in the magnitude of the for a given amount of stress being dependent stress. on the RATE of loading. All biological materials such as tendon and Strength vs. Stiffness Strength Stiffness Strength is necessary for load Stiffness is the materials bearing, and lightness is necessary resistance to load as the to allow movement. structure deforms Failure point or load sustained Modulus of elasticity before failure Slope of the load Failure is caused by: deformation curve - Single traumatic event - Accumulation of microfractures Bone is flexible and weak Assessed by: - Energy storage - Area under stress-strain curve Types of Loads Compression forces – Press the “ends” of the bone together Tension forces – Pulls or stretches bone apart – Produced by pull of contracting muscle – Occurs most often at an apophasis bony outgrowth Torsional forces – Twisting force – Creates a shear stress over the entire structure Shear forces – Sliding or slipping force – Adjacent parts of bone would experience equal and opposite forces. Influence of Bone 1. Magnitude 2. Frequency 3. Location 4. Variability 5. Direction 6. Rate of application 7. Duration Immovable Joints Synarthroses Permit shock absorption but not movement Sutures bone sheets bound at first by fibers fibers then ossify and are replaced by bone e.g. sutures of skull Syndesmoses bones bound by dense fibrous tissue extremely limited movement e.g. midradioulnar and midtibiofibular Slightly Movable Joints Amphiarthroses Cartilaginous joint Reduces/spreads shock and allows minimal motion Synchondroses joints held together by thin layer of hyaline cartilage e.g. sternocostal joints Symphyses thin plates of hyaline cartilage separated by a disc of fibrocartilage from the bone e.g. vertebral joints, pubic symphysis Freely Movable Joints Diarthroses or synovial joints Highly moveable 7 Types: 1. Gliding (Plane): nonaxial gliding is permitted 2. Hinge: Allows movement in one plane (uniaxial) 3. Pivot: Allows movement in one plane (uniaxial) 4. Condyloid: Allows primary movement in one plane 5. Ellipsoid: Allows movement in two planes (biaxial) 6. Saddle: Found only at the carpometacarpal articulation of the thumb 7. Ball and Socket: Surfaces are reciprocally convex and concave Function of Ligaments 1. Increase joint stability 2. Connects bone to bone 3. Guide normal joint motion 4. Restrict abnormal joint movement Muscular Considerations for Movement Responsible for movement of body and all of its joints Muscle contraction produces force that causes joint movement Muscles also provide – protection – posture and support – produce a major portion of total body heat Characteristics of Muscle 1. Irritability (i.e. excitability) Ability to respond to stimulation – stimulation provided by motor neuron releasing a neurotransmitter. – 2 only to nervous tissue in regards to sensitivity 2. Contractibility Ability to generate tension and shorten – can shorten by 50 70% of resting length 3. Extensibility Ability to stretch beyond resting length – external force required 4. Elasticity Ability to return to resting length after stretch Individual Muscle Organization Fascia – Sheet of fibrous tissue – Connective tissue Epimysium – Covers outside of muscle – Continuous with tendon – Houses groups of Fascicles – Transfers the various tensions to the tendon, providing a smooth application of the force to the bone. Fascicles – Bundles of muscle fibers – Covered by Perimysium Perimysium – Dense connective sheath – Covers fascicles – Protects fibers and provides pathways for nerves and blood vessels – The focus of flexibility training because the connective tissue in muscle can be stretched allowing the muscle to elongate. Fibers – Contained in fascicles – Each fascicle can contain as many as 200 fibers – Skeletal muscle cells – Parallel to each other – Covered by endomysium Endomysium – Membrane that covers fibers – Carries capillaries and nerves Sarcolemma – Directly under endomysium • a thin plasma membrane surface that branches into the muscle. • The neurological innervation of the muscle travels through the sarcolemma and eventually reaches each individual contractile unit by means of chemical neurotransmission. Myofibrils – Myosin & actin – Form sarcomere Muscle Fiber Types Type I Type IIa/IIx Slow Twitch Fast Twitch Highly Oxidative Minimally Oxidative Low force potential High Force potential Fatigue Resistance Easily Fatigued “Dark Meat” “White Meat” Stimulus Subthreshold stimulus – not strong enough to cause an action potential – does not result in a contraction Threshold stimulus – stimulus becomes strong enough to produce an action potential in a single motor unit axon – all of the muscle fibers in the motor unit contract Submaximal stimuli – Stimuli that are strong enough to produce action potentials in additional motor units Maximal stimuli – Stimuli that are strong enough to produce action potentials in all motor units of a particular muscle Factors affecting muscle tension development • Latent period – Brief period of a few milliseconds following stimulus • Contraction phase – Muscle fiber begins shortening – Lasts about 40 milliseconds • Relaxation phase – Follows contraction phase – Last about 50 milliseconds • Summation – When successive stimuli are provided before relaxation phase of first twitch has completed, subsequent twitches combine with the first to produce a sustained contraction • Tetanus – results if the stimuli are provided at a frequency high enough that no relaxation can occur between contractions Fusiform (Parallel) Muscles • Fascicles run length of muscle • Large degree of shortening • High velocity movements • Muscle fiber generally longer than tendon Penniform Muscles • Fibers run diagonally with respect to tendon • Featherlike in appearance • Fiber force in different direction to muscle force • the fibers are shorter than the muscle and the change in the fiber length is not equal to the change in muscle length. 3 types of penniform muscles 1. Unipennate 2. Bipennate 3. Multipennate Anatomical CrossSectional Area (ACSA) Sum total of all the crosssections of fibers in the muscle in the plane perpendicular to the direction of the tendon Physiological crosssectional area Sum total of all the crosssections of fibers in the muscle in the plane perpendicular to the direction of the fibers Muscle Attachment Muscle attaches to bone in 1 of 3 ways 1. Directly to bone: Fusion of epimysium to bone (trapezius) 2. Tendon: Tendon fused to muscle fascia (biceps brachii) 3. Aponeurosis: Sheath of connective tissue (abdominals) Roles of Muscle Stabilizers Act in one segment so that a specific movement in an adjacent segment can occur aka Fixators Neutralizer Muscle that contracts to eliminate unwanted movement caused by another muscle Synergist If more force is required these muscles assist the prime mover aka Assistant Movers Agonists Muscles primarily responsible for producing a given joint movement aka Prime Movers Antagonists Muscles who oppose the joint movement Must relax to allow movement One and Two Joint Muscles Passive Insufficiency – Inability of twojoint muscle to be stretched sufficiently to allow a complete ROM at all the joints it crosses because antagonists cannot be further elongated Active Insufficiency – Inability of twojoint muscle to produce force when joint position shortens the muscle to the point where it cannot contract (Finger flexion with Wrist Flexion)
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