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Adaptations to Bone, Muscle, and Connective Tissue

Adaptations to Bone, Muscle, and Connective Tissue. Chapter 4. Objectives. Describe the anatomy of bone, muscle, tendon and ligaments Discuss the response of the tissues above to training Design a program to stimulate growth of the above tissues. Bone Modeling.

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Adaptations to Bone, Muscle, and Connective Tissue

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  1. Adaptations to Bone, Muscle, and Connective Tissue Chapter 4

  2. Objectives • Describe the anatomy of bone, muscle, tendon and ligaments • Discuss the response of the tissues above to training • Design a program to stimulate growth of the above tissues

  3. BoneModeling • Wolff’s Law- bone responds by adapting to applied stress • Osteoblasts (formation of bone) • Osteoclasts (removal of bone) • Collagen matrix • Periosteum (outer covering) • Trabecular bone (spongy) • Cortical bone (solid)

  4. Skeleton • Axial skeleton- skull, spinal column • Appendicular skeleton- upper extremity, shoulder girdle, lower extremity, pelvic girdle

  5. Bone Hypertrophy • Minimal essential strain- the threshold stimulus for the formation of new bone • Activities must be weight-bearing to stimulate increases in bone density

  6. Bone Atrophy • Bone atrophy occurs with • Bed rest • Prolonged inactivity • Space travel • Osteoporosis • Menopause related • Age related • Female athletic triad (disordered eating, amenorrhea and osteoporosis. A female athlete can have one, two, or all three parts of the triad.

  7. Designing training programs to elicit osteogenic stimuli • Specificity of loading- perform exercises that stress the part of the skeleton where increases in bone density are desired • Axial loading • Exercise selection- force vectors through the spine and hip, multiple muscles, multi-joint, use greater absolute loads

  8. Designing training programs to elicit osteogenic stimuli • Progressive overload- gradually increase the training loads • Training variation- vary the selection of exercises to vary the distribution of forces

  9. Mechanical Loading of the Musculoskeletal System • Magnitude of the load (intensity) • Rate (speed) of loading • Direction of the forces • Volume of loading (sets x repetitions)

  10. Activity and Bone Density • Resistance exercise- few studies have looked at bone mineral density with resistance training, results are variable, no studies focus on the rate and magnitude of loading • Aerobic exercise- high intensity repetitive activities such as rowing, stair climbing, and running have been moderately successful in demonstrating bone mineral density increases

  11. Resistance Exercise Rx for Stimulating Bone Density • Volume 3-6 sets, up to 10 repetitions • Load- 1RM to 10RM range • Rest- 1-4 minutes • Variation- periodized • Exercise selection- structural exercises: squats, cleans, deadlifts, bench presses, shoulder presses

  12. Muscular Adaptation • Specific to fiber type recruited • Hypertrophy • Hyperplasia

  13. Training for Muscle Strength • High resistance, near maximal muscle actions, few number of repetitions, complete recovery between sets, stimulate FT muscle fibers

  14. Connective Tissue Adaptation • Type I collagen is a protein that is the major collagen fiber in bone, tendons, and ligaments • Fibroblasts, cells that synthesize new materials, synthesize procollagen • Procollagen consists of three strands of protein in a triple helix

  15. Microfibril- parallel arrangement of collagen filaments • Collagen “cross links” (covalent cross linking) to increase tensile strength • Collagen is in the extracellular space- outside the cell membrane

  16. Ligaments, Tendons, and Fascia • Ligaments- connect bone to bone • Tendons- connect muscle to bone • Fascia- fibrous covering of skeletal muscle • Endomycium, perimysium, epimysium

  17. Cartilage • Provide a smooth articulating surface between two bones in a joint • Act as a shock absorber • Aid in attaching muscles to bone • Limits translation

  18. Cartilage • Chondrocytes- cells that produce cartilage • Hyaline cartilage (articular cartilage) covers the ends of long bones • Ground substance- gel-like carbohydrate material in the type II collagen of cartilage • Fibrous cartilage- tough fibrous bundles of type I and type I collagen, intervertebral disks, menisci

  19. Tendons and Ligaments • In aerobic exercise, collagen metabolism increases to repair collagen damaged during exercise • In high intensity exercise, there is a net growth of connective tissue (ligaments and tendons) causing an increase in cross-sectional area and strength • Ligament/bone attachment is the weakest link in that system

  20. Changes in Tendon • Increase in collagen fibril diameter • A greater number of covalent cross-links within a fibril of increased diameter • An increase in the number of collagen fibrils • An increase in the packing density of collagen fibrils • Enhanced ability to withstand greater tensile forces

  21. Effects of Physical Activity on Cartilage • Cartilage gets its nutrient supply from synovial fluid • Joint movement (exercise) increases the nutrient supply to cartilage • Immobilization of a joint causes death of chondrocytes and resorption of cartilage matrix

  22. Moderate aerobic exercise increases cartilage thickness • Severe aerobic exercise or anaerobic exercise does not appear to cause degenerative joint disease

  23. Next Class • Chapter 21 Aerobic

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