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 ModelingWolff’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)

SkeletonAxial skeleton- skull, spinal

columnAppendicular skeleton-

upper extremity, shoulder girdle, lower extremity, pelvic girdle

Bone HypertrophyMinimal essential strain- the

threshold stimulus for the formation of new bone

Activities must be weight-bearing to stimulate increases in bone density

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.

Designing training programs to elicit osteogenic stimuliSpecificity 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

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

Mechanical Loading of the Musculoskeletal SystemMagnitude of the load

(intensity)Rate (speed) of loadingDirection of the forcesVolume of loading (sets x

repetitions)

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

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

Muscular AdaptationSpecific to fiber type recruited

HypertrophyHyperplasia

Training for Muscle StrengthHigh resistance, near

maximal muscle actions, few number of repetitions, complete recovery between sets, stimulate FT muscle fibers

Connective Tissue AdaptationType 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

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

Ligaments, Tendons, and FasciaLigaments- connect bone to boneTendons- connect muscle to boneFascia- fibrous covering of skeletal

muscleEndomycium, perimysium,

epimysium

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

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

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

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

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

Moderate aerobic exercise increases cartilage thickness

Severe aerobic exercise or anaerobic exercise does not appear to cause degenerative joint disease

Next Class

Chapter 21 Aerobic