Scientific Basis of Flexibility Training

Question 1

Muscular Flexibility

Answer 1

• ability of a muscle to lengthen
• allows joints to move through a ROM
• important part of muscle function
• PROM
• AROM
• depends on: ability of muscles to relax and lengthen, arthrokinematics and osteokinematics of joints, ability of connective tissue to be deformed
• achievement of ideal flexibility can prevent injury, enhance functional performance, assist in rehab of injury

Question 2

Loss of Muscular Flexibility

Answer 2

• decrease in ability of muscle to deform

- results in decreased joint ROM

Question 3

Stretching Exercise

Answer 3

• any process with the purpose of elongating soft tissue structures-we use mobilization when describing this process in nervous tissue
• we may wish to increase ROM, increase pathologically shortened tissues

Question 4

General Goals of a Flexibility Program

Answer 4

• increased joint ROM by altering muscle extensibility: stretching exercise increases joint ROM
• 3 main types of flexibility training: static, ballistic, PNF stretching

Question 5

Scientific Basis for Increasing Muscle Flexibility

Answer 5

• physical therapists must understand must understand muscle properties to effectively stretch a muscle
• mechanical properties of connective tissue
• neurophysiologic properties of connective tissue

Question 6

Mechanical Properties of Connective Tissue Anatomy

Answer 6

• contractile element (CE): undergoes some change with stretch
• series elastic component (SEC): connective tissue component, lies in series with muscle fibers
• parallel elastic component (PEC): connective tissue component, lies parallel with muscle fibers

Question 7

Mechanical Properties of Muscle

Answer 7

• muscle stiffness describes resistance to deformation
• connective tissue provides most of muscle’s mechanical stiffness
• properties of connective tissue are largely determined by its extracellular matrix: water, fibrous components, proteoglycans, glycoproteins

Question 8

Components of Connective Tissue

Answer 8

• water: integral component, allows connective tissues to stretch and rebound
• fibrous components: elastin and collagen both resist tension, elastin has greater rebound and lesser tensile strength, collagen has greater tensile and less rebound
• proteoglycans: have tendency to attract water, thus serve to maintain space between collagen fibers
• glycoproteins: stabilize extracellular matrix

Question 9

Connective Tissue Composition: Collagen Fibers

Answer 9

• 30% of the protein in the human body
• provides strength and stiffness
• resist tensile deformation
• fiber orientation varies with tissue
• skin: fibers are random, poor at resisting tension
• tendons: fibers are more parallel, good at resisting tension
• joint capsule, ligaments, and fascia: variable orientation, more load, more parallel orientation

Question 10

Deformation of Connective Tissue

Answer 10

• zone : toe region, removes crimp in tissue
• zone II: elastic region, region of tissue resistance
• zone III: plastic region, region of microfailure
• zone IV: complete failure, seen with manipulation, etc
• PTs work primarily in zones II and III

Question 11

Deformation of Connective Tissue: Viscoelasticity

Answer 11

• dual nature of tissues: viscosity, elasticity
• time and load dependent
• tissue relaxes when load removed
• allows slow loading and slow tissue relaxation
• ex: tx on fx femur, tx on scoliosis

Question 12

Factors Affecting Collagen Connective Tissues

Answer 12

• activity level
• immobilization
• age
• corticosteroids (make CT way more brittle, decreases elasticity)
• temperature

Question 13

Contractile Tissue Response to Stretch: Acute Response

Answer 13

• some mechanical disruption of cross bridges
• filaments slide apart
• sarcomeres return to resting length
• SEC and PEC change elastically
• net effect: lesser tissue stiffness

Question 14

Contractile Tissue Response to Stretch: Chronic Adaptation

Answer 14

• sarcomeres: added or removed, to accommodate new length
• increased connective tissue production: when immobilized in a shortened position, a means to protect the muscle when stretched
• net effect: muscle usually generates less force from less effective position

Question 15

Neurophysiologic Properties of Connective Tissue

Answer 15

• muscle spindle fibers
• golgi tendon organs
• autogenic inhibition
• reciprocal inhibition

Question 16

Muscle Spindle Fibers

Answer 16

• contribute to proprioception
• located within muscle belly
• specialized receptor consisting of: unique muscle fibers (intrafusal fibers), sensory endings, motor endings
• intrafusal fibers connecting to extrafusal fibers: thus, stretching muscle stretches muscle spindle
• sensory ending respond to changes in: muscle length, velocity of change in length
• quick stretch –> message to CNS –> protective muscle contraction
• type Ia –> spinal cord –> alpha motor unit
• resists attempt of muscle to elongate

Question 17

Golgi Tendon Organs (GTOs)

Answer 17

• contribute to proprioception
• encapsulated at junction of extrafusal fibers and tendons
• attached in series
• sensitive to change in tension: passive stretch, active muscular action
• serves to prevent overactivity of alpha motor neurons
• GTO fibers with overstimulation: prolonged stretch, prolonged isometric action
• GTO –> type Ib sensory nerve –> spinal cord –> inhibition of MU
• can override input from muscle spindle fiber
• thus allows relaxation –> elongation

Question 18

Autogenic Inhibition

Answer 18

• stimulation of muscle causing its neurologic relaxation
• occurs with activation of GTO
• serves as basis for static stretching and some PNF stretching techniques

Question 19

Reciprocal Inhibition

Answer 19

• stimulation of muscle causing neurologic relaxation of its antagonist
• helps ensure ability to move through available ROM
• serves as basis for some PNF stretching techniques

Question 20

Static Stretching

Answer 20

• muscle is slowly elongated
• positioned to tolerance and maintained
• individual feels in this position: mild tension, mild discomfort
• extreme pain or discomfort should be avoided
• slow, prolonged stretch helps to: circumvent muscle spindle reflex, facilitates muscle inhibition via GTOs
• thus combined neuro effect is to minimize influence of muscle spindle fibers, maximize influence of GTOs

Question 21

Application of Static Stretching

Answer 21

• most research done on LE
• duration of 15-60 sec
• results: 30-60 sec consistently found more effective than 15 sec or no stretching
• recent studies consistently show decreased force immediately following: vertical jump, 40 yd dash

Question 22

Ballistic Stretching

Answer 22

• imposes high tension on stretched muscle
• consists of repetitive bouncing movements
• invokes muscle spindle fiber reflex arc
• research indicates increased muscle flexibility
• some concerns re: potential for muscle injury

Question 23

Application of Ballistic Stretching

Answer 23

• used less commonly in fitness or rehab settings: start with static stretching and progress based on individual ability/need
• yet if used appropriately: plays important role in training athletes, secondary to highly ballistic nature of most athletic activities
• not recommended where injury is a possibility: elderly, post-immobilization, joint instability, acute injury
• must monitor more closely

Question 24

Proprioceptive Neuromuscular Facilitation (PNF) Stretching

Answer 24

• developed by Knott and Voss
• promoting or hastening the response of a neuromuscular mechanism through stimulation of proprioceptor
• PNF has both flexibility and strengthening components
• research indicates: PNF stretching is effective for increased flexibility
• no consensus on which PNF technique is best

Question 25

PNF Stretching

Answer 25

• terminology has varied and thus some confusion exists
• some of confusion secondary: Knott and Voss originally described stretching exercises in diagonal patterns, many clinicians now apply in cardinal planes
• a number of PNF techniques exist

Question 26

PNF: Hold-Relax

Answer 26

• limb passively moved to end ROM
• individual applies 10s isometric of agonist against immovable resistance: stimulates GTO –> autogenic inhibition –> relaxation
• limb passively moved to new end ROM: held in static stretch 10-30 sec
• may be repeated 3-5 times before returning to starting position

Question 27

PNF: Contract-Relax

Answer 27

• limb passively moved to end ROM
• individual applies 10s isometric of antagonist against immovable resistance: stimulates reciprocal inhibition –> relaxation of agonist
• limb passively moved to new end ROM: held in static stretch, 10-30 sec
• may be repeated 3-5 times before returning to starting position

Question 28

Short Duration Stretching

Answer 28

• maintain at least 30 seconds
• ex: manual traction, static stretching
• stretches both contractile and non-contractile structures
• repeat several times
• changes in length: transient (short term), due to sarcomere give, realigning of collagen fibers, changes in neuroregulation

Question 29

Long Duration Stretching

Answer 29

• low intensity stretch
• ex: various traction devices,dynamic splints
• maintained 20+ minutes
• changes in length: due to increased number of sarcomeres over time, noncontractile tissue undergoes plastic deformation (creep)

Question 30

Benefits of Increased Flexibility

Answer 30

• increased ROM
• improved capacity for circulation and oxygen exchange
• muscle stiffness: facilitates easier, smoother muscular action
• decreased soreness associated with other physical activity
• improved body awareness
• decreased muscular tension, increased relaxation
• maintain ease of movement
• improved coordination

Question 31

Clinical Guidelines for Stretching

Answer 31

• research has yet to identify one method as most beneficial for all applications: static, ballistic, and PNF all increased flexibility
• static stretching easiest to used: but linked to decrease performance for many activities
• greatest risk for ballistic: but most beneficial for athletes
• PNF requires greatest expertise and 2nd individual

Question 32

Clinical Guidelines for Static Stretching

Answer 32

• isolate muscle or muscle group to be stretched
• ensure proper position and alignment
• stretch only through normal joint ROM
• stretch to point of discomfort and hold
• hold endpoints progressively for a minimum of 30 seconds
• perform 3-4 reps for each major muscle group
• emphasize proper breathing during stretch
• ASCM recommends 2-3/week
• attempt to integrate stretching into client’s daily routine
• ideally stretch after activity
• strengthen muscle in newly acquired ROM
• comfort in positioning –> ANS –> more effective stretching

Question 33

Contraindications for Flexibilit Training

Answer 33

• recent unhealed fracture
• local hematoma
• joint motion limited by bony block
• sharp pain during stretch
• uncontrolled muscle cramping whit attempt to stretch
• infection affecting joint or surrounding tissues
• acute inflammation affecting joint or surrounding tissues
• when contracture improves function: tenodesis grasp of quadriplegic
• exercise particular caution in patients with: known or suspected osteoporosis, weak muscles

Question 34

Take Home Messages

Answer 34

• muscular flexibility is a component of comprehensive exercise testing and prescription
• flexibility is the product of many factors: mechanically, neurophysiological, lifestyle
• static ballistic and PNF stretching each have relative merits and drawbacks
• physical therapists should be able to appropriately integrate flexibility exercise into fitness and rehab programs