Adaptations to Bone, Muscle, and Connective Tissue

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Adaptations to Bone, Muscle, and Connective Tissue

• Chapter 4

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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

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Bone Modeling

• Wolffs 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)

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Skeleton

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

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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

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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.

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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

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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

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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)

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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

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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

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Muscular Adaptation

• Specific to fiber type recruited
• Hypertrophy
• Hyperplasia

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Training for Muscle Strength

• High resistance, near maximal muscle actions, few
  number of repetitions, complete recovery between
  sets, stimulate FT muscle fibers

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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

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• 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

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Ligaments, Tendons, and Fascia

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

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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

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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

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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

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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

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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

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

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Next Class

• Chapter 21 Aerobic