Kinesiology Week 2 Notes
Kinesiology Week 2 Notes MOV 300
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This 54 page Class Notes was uploaded by Maria D'Angelo on Wednesday February 3, 2016. The Class Notes belongs to MOV 300 at Grand Valley State University taught by Dr. Krisanne Chapin in Winter 2016. Since its upload, it has received 20 views. For similar materials see Kinesiology in Cinema And Media Studies at Grand Valley State University.
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Date Created: 02/03/16
Understanding Bones: Objec▯ves • Explain how material contents and structural organiza▯on of bone aﬀect its ability to withstand mechanical loads. • Describe normal growth and matura▯on of bone. • Describe the eﬀects of exercise and of weightlessness on bone. • Explain the signiﬁcance of osteoporosis. •of mechanical loading and common bone forms injuries. Adult Skeleton • 206 bones • Axial skeleton • 80 bones • Appendicular skeleton • 126 bones Purpose of Skeleton • Protec▯on of heart, lungs, brain, etc. • Support to maintain posture • Movement by serving as points of a▯achment for muscles and ac▯ng as levers • Mineral storage such as calcium & phosphorus • Hemopoiesis • process of blood cell forma▯on in the red bone marrow Shapes of Bones • Long bones • Long cylindrical sha▯ • Ex. Phalanges, metatarsals, radius, ulna, humerus femur, • Short bones • Small cubical shaped, solid bones • Ex. Carpals, tarsals Shapes of Bones • Flat bones • Usually have a curved surface & a▯ach to very thin tendons • Ex. ilium, ribs, sternum, clavicle, & scapula • Irregular bones • Spine, ischium, pubis, maxilla • Sesamoid bones • Small bones imbedded within the tendon of a musculotendinous unit • the mechanical advantage of musculotendinous unit Bone Makeup • Calcium carbonate and • water Calcium phosphate • 25-‐30% bone weight • 60-‐70% bone weight • Contributes to bone • Gives bone its s▯ﬀness strength • Primary determinant for • Provides transporta▯on compressive strength. for nutrients and wastes • Other minerals • Collagen-‐ protein • Gives bone its ﬂexibility • Sodium • Contributes to tensile • Fluoride strength Bone Types • Categories of bone based on porosity: • Cor▯cal bone -‐ compact mineralized bones with low porosity; be▯er at withstanding stress Cortical bone • Sha▯s of long bones Trabecular bone • Trabecular (or cancellous) bone-‐ less compact mineralized bone with high porosity that is be▯er at withstanding strain • Found in the ends of long bones and vertebrae Mechanical loading basics • absorbed by the ▯ssues of the body & • loads or external forces may cause these • Internal forces • Muscles can ac▯vely generate internal force • Tension in tendons, connec▯ve ▯ssues, ligaments and joints capsules may generate passive internal forces • Internal forces can • connec▯ve ▯ssues islocate joints, disrupt muscles & Mechanical loading basics • External forces produced from outside the body • Gravity , iner▯a or direct contact • All ▯ssues, in varying degrees, resist changes in their shape • To prevent injury or damage from ▯ssue deforma▯on the body must be used to absorb energy from both internal & external forces Mechanical loading basics • It is advantageous to absorb force over larger aspects of our body rather than smaller and to spread the absorp▯on rate over a greater period of ▯me • Stronger and healthier ▯ssues are more likely to withstand excessive mechanical loading & the resultant excessive ▯ssue deforma▯on Mechanical loading basics • mechanical loading may result from diﬀerent types of loads Composi▯on and Structure of Bone • Bone is Anisotropic r • it has diﬀerent t strength and r O l S s▯ﬀness n E depending on u P e O N the direc▯on of t C S the load S E R T E S The Eﬀects of Loading • stress– load applied • Strain (deforma▯on) – change in shape • This rela▯onship is described in the Stress/ Strain Curve Stress/Strain Curve Brittle Material Elastic Limit Ductile material Load (Stress) Deformation (Strain) Elastic & Plastic responses Elastic Plastic region region ) a o fracture/ ( failure s r S elastic – can return plastic response leads to fracturing (cannot return) Strain (Deformation) Stress – Strain Curve Stress-‐Strain Curve Cor▯cal bone Cancellous/trabecular Tendons Ligament Car▯lage Stress-‐Strain Curve • Anisotropic -‐ Bone responds to diﬀerent loads diﬀerently • Compression> tension • Tension > Shear • Loads applied at higher rate • Bone becomes s▯ﬀer • Sustains higher load • St• What if it breaks? Adapted from Nordin M & Frankel VH (2001). Basic Biomechanics of the Musculoskeletal System.(p.54) Repe▯▯ve vs. Acute Loads • Repe▯▯ve loading • Subacute, rela▯vely low magnitude • Microtrauma • Carpal tunnel, stress fractures • Acute loading • Single force of suﬃcient magnitude to cause injury • Macrotrauma • Car accidents Typical Bony Features • Diaphysis– long cylindrical sha▯ • Cortex -‐ hard, dense compact bone forming walls of diaphysis • Periosteum -‐ dense, ﬁbrous membrane covering outer surface of diaphysis Typical Bony Features • Endosteum • lines the inside of the cortex • Remodelling bones and releasing minearals •– between walls of y diaphysis, containing yellow or fa▯y marrow Typical Bony Features • Epiphysis • cancellous (spongy or trabecular) bone • Epiphyseal plate • Growth plate • thin car▯lage plate separates diaphysis & epiphyses • Ar▯cular (hyaline) car▯lage • covering the epiphysis to provide cushioning eﬀect & reduce fric▯on Bone Growth & Development • Endochondral bones • grow rapidly into structures shaped similar to the bones which they will eventually become • growth con▯nues and gradually undergoes signiﬁcant change to develop into long bone Embryonic Childhood & fetal dev. & Adolescence Bone Growth & Development • Longitudinal Growth • At the epiphyseal plate, car▯lage transformed into bone • Con▯nues as long as epiphyseal plates are open • Stops ~18 yrs of age • can be seen up to 25 yrs of age • Circumferen▯al Growth • Diameter increases throughout lifespan • Most rapid growth before adulthood • Internal layer of periosteum builds new concentric layers on old layers Newborn 2 yrs 17-18 yrs 30-40 yrs 80 years Bone Growth Car▯lage replaced bone None remodeled Car▯lage growth in epiphyseal plate Bone Growth & Development Bone Response to Stress • Wolﬀ’s Law • Bone adapts (grows) according to stress applied to it. • & magnitude of forces that are habitually applied to them • Form Follows Func▯on or Func▯on Determines Structure Bone Response to Stress • Specialized cells called osteoblasts build new osteoclasts resorb bone ▯ssue • Osteoblasts – “Blasts Build Bone” • resorb bone cells that • mechanical stress (or lack predominance of o a osteoblast or osteoclast ac▯vity, respec▯vely. Bone Response to Stress • Bone mineral density is propor▯onal to body weight • Body weight provides most constant mechanical stress • Think: weight gain or loss and its eﬀect on bone density • Rank 6 diﬀerent athletes according to bone density of the femoral head Wolﬀ’s Law in Ac▯on Wolﬀ’s Law in Ac▯on • Amputee • much diﬀerent than sound side prosthe▯c side • Bone spur • Excessive forces causing “spurs” to develop • Examples from Hall • Infant born without a ▯bia, ﬁbula remodeled • but 5 ﬁnger, sing all • A▯er 32 years, ﬁnger remodeled to contralateral 3 ﬁnger r to Wolﬀ’s Law in Ac▯on: Bone Markings • Processes that form joints • E.g., condyles, facets, heads • Processes to which ligaments, muscles or tendons a▯ach • e.g., Epicondyle, spine, trochanter • Cavi▯es (depressions) -‐ including opening & grooves • e.g., fossa, foramen, sulcus Bone Hypertrophy • mass due to predominance of osteoblas▯c ac▯vity. • In response to regular physical ac▯vity • Ex: tennis players have muscular arm. one hypertrophy in playing • more mineraliza▯on of the bone. he • Propor▯onal to amount of impact of ac▯vity/sport • Physically ac▯ve> density than sedentary Bone Atrophy • A decrease in bone mass resul▯ng form a predominance of osteoclast ac▯vity • Results in decreased • Bone calcium • Bone weight and strength • Seen in bed – ridden pa▯ents, sedentary elderly, and astronauts Bone Atrophy • Astronauts • Overall cause is unknown • Tend to have nega▯ve calcium ra▯o • Increase in calcium excre▯on • Hypothesis: • Changes in bone blood ﬂow due to diﬀerence in gravita▯onal ﬁeld • To help maintain bone and muscle, astronauts exercise with straps holding them down on specialized treadmill surfaces Bone Changes in Aging • Progressive loss of collagen and related increase in bone bri▯leness • Increasing loss of bone substance • Increasing porosity of both bone types •leads to weakness integra▯on of trabeculae • A▯er age 60, ~90% of all fractures in adults are osteoporosis-‐related Bone Changes in Aging • Women • Peak bone mineral content: 33-‐40 yoa • 0.5%-‐1.0% loss per year following age 50 or menopause • 6.5% loss per year post-‐menopause for ﬁrst 5-‐8 years • By ~75 yoa, females have 50% of the bone mass at 30 yoa • Men • Peak bone mineral content: 19-‐33 yoa • Lose bone at 2/3 the rate of females Bones: Men vs. Women Osteoporosis • Deﬁni▯on-‐ A disorder involving decreased bone mass and strength with one or more resul▯ng fractures. • Starts as osteopenia-‐ reduced bone mineral density that predisposes to fractures. • Type I Osteoporosis = post-‐ menopausal Osteoporosis • Aﬀects about 40% of women over 50 • Type II Osteoporosis = Age-‐Associated Osteoporosis • Aﬀects most women and men over 70 • Diﬀerences between men and women: Men reach higher peak bone mass and strength in young adulthood Osteoporosis • Symptoms: • Painful, deforming and debilita▯ng crush fractures • Usually of lumbar vertebrae from height loss ac▯vity, which leads to • Es▯mated 26% of women over 50 suﬀer from these fractures • Back pain most common • Thoracic Kyphosis – “Dowager’s Hump” • Due to body weight being anterior to spine o▯en wedge shaped fx’s. Osteoporosis Treatment • Risk factors for • Easier to prevent than osteoporosis to treat • Physical inac▯vity • Adequate Vitamin D • Excessive thinness • Increased dietary calcium • Tobacco smoking • Hormone replacement • Deﬁciencies in estrogen, therapy calcium, and vitamin D • Weight bearing physical • Excessive consump▯on of ac▯vity protein and caﬀeine • Gene▯c factors Osteoporosis Treatment • Future use of pharmacologic agents • May s▯mulate bone forma▯on • Low doses of growth factors to s▯mulate osteoblast recruitment and promote bone forma▯on • Best Bet: • Engaging in regular physical ac▯vity • Avoiding the lifestyle (risk) factors that nega▯vely aﬀect bone mass. • decreased bone density 5-‐10% by the ▯me of menopause. Female Athlete Triad • Disordered Ea▯ng • Aﬀects 1-‐10% of all adolescent and college-‐age women • Displayed in ~62% female athletes • Mostly in endurance or appearance-‐related sports • Amenorrhea • Cessa▯on of the menses • O▯en a side-‐eﬀect of disordered ea▯ng • Osteoporosis • Decrease in bone mass and strength Ea▯ng Disorders • Rela▯vely common among girls 15-‐19 • Anorexia Nervosa Symptoms • Body weight 15% below normal for age/height • Intense fear of gaining weight, disturbed body image • Bulimia Nervosa Symptoms • Minimum of 2 ea▯ng binges a week for a few months • Feeling a lack of control in binging • Regular use of self-‐induced vomi▯ng, laxa▯ves, diure▯cs, strict die▯ng, excessive exercise Amenorrhea • 3-‐5% of pre-‐menopausal women in US have amenorrhea • Primary amenorrhea –delayed menarche beyond age 16 • Less than 1% of girls in overall popula▯on • Up to 22% of girls in cheerleading, diving, gymnas▯cs • Secondary amenorrhea – absence of 3-‐6 cycles • 2-‐5% of general popula▯on • 69% of dancers, 65% of long distance runners Amenorrhea • Estrogen deﬁciency • Increases bone resorp▯on • Disordered ea▯ng → energy deﬁciency → altered bone metabolism and → decreased bone density • Amenorrhic pre-‐menopausal females have an increased rate of stress fractures • Loss of bone may be irreversible • Long term implica▯ons? Bone Injuries • Fractures-‐ most common • Simple • Compound • Avulsion • Impacted or buckled • Depressed • Greens▯ck • Spiral • Stress Bone Injuries • Bone stronger in resis▯ng compression than tension, so the side loaded with tension will fracture ﬁrst • Acute compression fractures (in absence of osteoporosis) is rare • Stress Fractures occur when there is no ▯me for repair process (osteoblast ac▯vity) • layers of cor▯cal bone in con▯nuity of outer Epiphyseal Injuries • Include injuries to: • Car▯laginous epiphyseal plate • Ar▯cular car▯lage • Represent ~ 35% of all skeletal injuries in children • Most common in 10-‐15 year old children • Acute and repe▯▯ve loading can injure growth plate • Leads to premature closing of epiphyseal junc▯on and termina▯on of bone growth. Summary • Bone is an important living ▯ssue that is con▯nuously being remodeled. • Bone strength and resistance to fracture depend on its material composi▯on and organiza▯onal structure. • Bones con▯nue to change in density throughout the life span.
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