Principles of Stretching

Question 1

What is stretching?

Answer 1

Manual or mechanical techniques to improve mobility.

Question 2

Properties of Soft Tissue: Response to Immobilization and Stretch

Answer 2

• Elasticity (think rubber band)
• Viscoelasticity (remember the weight on the tree limb in Kines textbook?)
• Plasticity (what happens after a plastic toy is heated and stretched?)

Question 3

Composition of Collagen Fibers

Answer 3

resist tensile deformation and are responsible for the strength and stiffness of tissue

Question 4

Composition of Elastin fibers:

Answer 4

provide extensibility

Question 5

Composition of Reticulin Fiber

Answer 5

provide tissue bulk

Question 6

Composition of Ground Substance

Answer 6

organic gel made of water, proteoglycans (PGs), and glycoproteins; provides hydration, stabilization, and resists compressive forces

Question 7

Mechanical Behavior of Noncontractile Tissue

Answer 7

• Collagen absorbs most of the tensile stress
• Fails at < 10% increase in fiber length
• Elastin can lengthen to 150% of resting length without failure
• Collagen is 5x stronger than elastin

Question 8

• Alignment of Collagen Fibers
  
  • Tendons:

Answer 8

parallel, resist greatest tensile load

Question 9

• Alignment of Collagen Fibers
  Ligaments, joint capsules, and fascia:

Answer 9

variable alignment – can resist multidirectional forces

Question 10

Alignment of Collagen Fibers
Skin

Answer 10

random orientation, limited resistance to tensile loads

Question 11

Changes in collagen affecting stress-strain response:
- 1.Effects of immobilization

Answer 11

• ↓ in size/amount of collagen (weakening)
  - Adhesions: cross linking of disorganized collagen

Question 12

Changes in collagen affecting stress-strain response:
2.Effects of inactivity (decrease of normal activity)

Answer 12

↓ max tensile strength

Question 13

Changes in collagen affecting stress-strain response:
3.Effects of age

Answer 13

• ↓ tensile strength, adaptation to stress is slower
• Susceptible to overuse and tears

Question 14

Changes in collagen affecting stress-strain response:
4.Effects of corticosteroids

Answer 14

↓ tensile strength – Achieve plastic deformation sooner

Question 15

Changes in collagen affecting stress-strain response:
5.Effects of injury and remodeling of tissue

Answer 15

(3 weeks – 1 year)

Question 16

Mechanical Principles of Stretching Connective Tissue

Answer 16

• Stretch deformation depends on magnitude of loading and rate of load application
• Permanent changes in tissue length and flexibility requires breaking collagen bonds and realignment of fibers.
• Must allow time after stretching for healing adaptive remodeling of tissues

Question 17

Mechanical Principles of Stretching Connective Tissue
KEY POINT

Answer 17

Must use any new gained range to allow remodeling of tissue and to train the muscle to control the new range

Question 18

Rate dependence:

Answer 18

• tissue becomes stiffer when load is applied at a high rate (protective response)
  
  • Apply stretch gradually to minimize rate-dependent response

Question 19

Creep:

Answer 19

• occurs when a gradually increasing external load is applied to connective tissue and sustained: tissue will continue to elongate during the maintained stretch
  
  • Long-duration stretch takes advantage of this tissue property

Question 20

Stress-relaxation

Answer 20

gradual decrease in the force required to maintain the amount of deformation of the tissue
- Underlying principle for prolonged stretching procedures

Question 21

Noncontractile connective tissue structures

Answer 21

Primary source of muscle resistance to passive elongation

Question 22

Passive stretch to muscle:

Answer 22

• Tension rises in series elastic component
• Mechanical disruption of cross-bridges as myofilaments slide apart
• Lengthening of sarcomeres
• Sarcomeres return to resting length when stretch force is released

Question 23

• Mechanical Response of the Contractile Unit to Immobilization
  
  • Immobilization in a shortened position:

Answer 23

• Reduction in muscle length, number of muscle fibers, and number of sarcomeres
  
  • Result is decreased muscle length, atrophy and weakness
  • Shift to the left in length-tension curve, decreasing capacity to produce max tension when contracting at its normal resting length

Question 24

• Response of the Contractile Unit to Immobilization and RemobilizationMorphological changes:

Answer 24

• Decay of contractile protein
• Decreased muscle fiber diameter and number of myfibrils
• Result is atrophy and weakness
• Increased fibrous and fatty tissue in muscle
• Occurs more quickly in tonic muscle fibers than phasic muscle fibers

Question 25

Muscle Spindle

Answer 25

- The major sensory organ of muscle - Monitors the velocity and duration of stretch - Senses length changes in muscle and the velocity of those changes

Question 26

GTO

Answer 26

- Sensitive to tension in muscle caused by - passive stretch - active muscle contraction - A protective mechanism - “Autogenic inhibition”: - When excessive tension develops in a muscle, the GTO fires, causing inhibition and decreasing tension in the muscle

Question 27

- Neurophysiologic Response of Muscle to Stretch - Stretch Reflex

Answer 27

- Response of muscle to a quick or sustained stretch - Intrafusal muscle fibers in the spindle sense length change - Afferent signals to spinal cord activate extrafusal muscle fibers - Result is an increase or facilitation of active tension in the muscle that is stretched - This increased tension resists lengthening of the muscle (limits ability to stretch muscle) - Decreased activity (inhibition) in the muscle on the *opposite* side of the joint may occur, this is known as “reciprocal inhibition”

Question 28

Interventions to Increase Mobility of Soft Tissues

Answer 28

- Stretching: Manual or Mechanical/Passive or Assistive - Self-Stretching - Neuromuscular Facilitation and Inhibition - Muscle Energy Techniques - Joint Mobilization/ Manipulation - Soft Tissue Mobilization/ Manipulation - Neural Tissue Mobilization

Question 29

- Determinants of Stretching Interventions - Alignment

Answer 29

- Stretch force must be directed to appropriate muscle group - Distance between origin and insertion must be maximized

Question 30

Determinants of Stretching Interventions Stabilization

Answer 30

Prevents muscle attachment sites from moving during the stretch

Question 31

Determinants of Stretching Interventions Intensity of Stretch

Answer 31

Apply at a low intensity using a low load

Question 32

Determinants of Stretching Interventions Duration of Stretch

Answer 32

- How long a single cycle of stretch is applied - Cumulative time of all stretch cycles: total elongation time - Lack of agreement: ideal stretch duration and number of repetitions

Question 33

Static stretching:

Answer 33

elongation of soft tissues just beyond the point of tissue resistance and held in the lengthened position with a sustained stretch force over a period of time

Question 34

Median duration of static stretching is

Answer 34

30 sec

Question 35

Static progressive stretching:

Answer 35

held in lengthened position until relaxation of the tissue is felt, then incrementally lengthened further and again held at at the new end range position

Question 36

Cyclic stretching:

Answer 36

short-duration stretch force repeatedly but gradually applied, released, and reapplied multiple times

Question 37

Slowly applied stretch is BEST:

Answer 37

- Minimizes muscle activation - Reduces risk of injury - Reduces post-stretch muscle soreness - Less tensile stresses on connective tissue - Less likely to activate stretch reflex - Moderates viscoelastic effects of connective tissue - Safer than a high-velocity stretch

Question 38

Ballistic Stretching

Answer 38

- Rapid, forceful intermittent stretch - High-velocity and high-intensity - Fast joint movement that quickly elongates the targeted soft tissues - Can improve flexibility as well as static stretching - Causes greater trauma to stretched tissues and more muscle soreness than static stretching

Question 39

Ballistic Stretching Indications

Answer 39

- Young healthy people participating in a conditioning program - Highly trained athletes - Young active individuals in the final phase of rehabilitation

Question 40

Ballistic Stretching Contraindications

Answer 40

- Elderly or sedentary individuals - People with musculoskeletal pathology or chronic contractures