Extrinsics & Intrinsics & Isometrics

Extrinsics & Intrinsics & Isometrics

• Extrinsics: Technique done externally on clients’ dysfunctional tissue; works by affecting Nervous System

• Neurophysiological Effects

  • Muscle Spindle Adaptation: Flower spray receptors reset at a lower resting tone

  • Tendon Reflex / GTO Effect: Tension in the tendon helps the muscle let go & decrease tone

  • Mechanoreceptor Stimulation: Decreases pain by blocking nociceptor stimulation

• Mechanical Effects

  • Nerve Impulse Route ReRouting: Nerve pathway will reroute around the section blocked by thumb

  • Reflexive Hyperemia: Brings blood & oxygen to the area

• Intrinsics: Techniques initiated by the client & guided by the therapist; the muscular contraction of the client will initiate the neurological impulse needed

  • 3 Types:

• Isometrics

  • Utilizes GTO Effect to gain ROM; is applied at first barrier of resistance with resistance

  • Application

    • Applied at first point of resistance

    • Client contracts while you provide unyielding resistance

    • Application for 7 seconds; repeat 3x

  • Effect

    • Stimulates GTO without stimulating Spindle

• Isotonics

  • Uses muscle fibre recruitment which is applied through a full ROM with yielding restistance

  • Application

    • Applied at end range of motion

    • Patient contracts as you offer adequate resistance to require muscle fiber recruitment but not enough to prevent muscle going through ROM

  • Effect

    • Annulospiral alters muscle length thus stimulating Annulosprial without GTO

• Reciprocal Inhibition

• Applied to Antagonist of hypertonic muscle

Theory

• Muscles

• Consist of Two Main Structures:

  • Muscle Cells (Muscle Fibres)

  • Connective

• Epimysium: Connective tissue covering entire muscle belly; forms tough tendinous cords @ muscle ends which attach to periosteum (bone)

• Endomysium: Connects muscle cells to each other; intertwines with perimysium

• Perimysium: Connects fascicles; intertwines with epimysium

• Muscle Fibre

• Each contains specialized receptors which monitor the degree of contraction occuring within the bundle:

  • Muscle Spindle (Muscle Bundles in the Bellies)

  • Golgi Tendon Organs (Musculotendinous Junction)

• Muscle Spindle: Tiny structures with 3-10 intrafusal fibres per spindle; surronded by a fascia cocoon

• Two Intrafusal Fibres:

  • Nuclear Bag Fibers:

    • Central area has nuclei only (no actin/myosin)

  • Nuclear Chain Fibers:

    • Cylindrical, similar to muscle fibers

    • Actin & Myosin present

• Innervation

  • Sensory:

    • Type la (Annulospiral Receptor): Wraps around nuclear bag fiber center responds quickly;y to onset of stretch; initiates stretch reflex

    • Type ll (Flower Spray Receptor): Contacts both fiber types; responds to ongoing tension to help maintain tone

  • Motor: Spindles recieve motor input to adjust sensitivity

  • Function:

    • Both receptors monitor muscle length but serve different roles

    • Annulospiral: Detects sudden stretch, sends rapid signal to spinal cord for reflexive contraction

    • Flower spray: Detects sustained tension, helps regulate resting tone and prevent overstretching

    
    

• Golgi Tendon Organ

• Collagen fibers in a thin connective tissue capsule; located as musculotendinous junction

• Innervation:

  • Sensory:

    • Type lb: lb fibers contact collagen, send information to spinal cord

    • Synapse with interneurons:

      • Some ascend sensory tracts

      • Some inhibit alpha/gamma motor neurons

    • Inhibitory interneurons release glycine, hyperpolarizing motor neurons

      • Result: reduced contraction / reduced muscle tone

  • Function: protect muscle from excessive tension

• Nerve & Blood Supply

• Motor Neurons Connect CNS to Muscles

• Two types:

  • Alpha motor neurons → extrafusal fibers (cause contraction)

  • Gamma motor neurons → intrafusal fibers (adjust spindle sensitivity)

• Alpha and gamma systems usually work together for coordinated movement

• Gamma activity maintains spindle tension during muscle contraction

• Motor control is both reflexive and brain-directed

• Motor unit = one motor neuron + all muscle fibers it innervates

  • Fewer fibers per motor unit → fine control (e.g., hand)

  • More fibers per unit → gross control (e.g., hamstrings)

• Muscle Tone

  • Muscle tone = constant, low-level involuntary contraction of some motor units

    • Keeps muscle firm and ready for action

    • Present in living tissue only

  • Other types of contractions:

    • Isometric: tension without change in muscle length or joint movement

    • Isolytic: forced lengthening when external force overcomes muscle effort

    • Isotonic: muscle changes length during contraction

      • Concentric: muscle shortens while producing force

      • Eccentric: muscle lengthens while producing force

• Alterations in Muscle Tone

  • Hypertonicity (Excess Tone)

    • Elevated spindle activity → increased CNS input → more muscle tension

    • Neuronal adaptation: trauma/sustained stimuli alter neuron threshold (e.g., from -70 mV to -60 mV), increasing sensitivity

    • Inadequate ATP: lack of ATP (due to low O₂/glucose) prevents actin-myosin separation, increasing tension

  • Hypotonicty (Low Tone)

    • Elevated GTO stimulation → inhibits motor output

    • Nerve entrapment/impingement → reduced motor signals due to pressure on nerve roots or along nerve path