7.2 Flexibility, Stretching Techniques, and Joint Range of Motion
Key Takeaways
Spindles signal length and length change. Ia afferents contribute to the stretch reflex.
Golgi tendon organs signal tension through Ib afferents. Spinal force feedback varies with task and loading.
Choose a tolerable stretch dose and reassess. Describe PNF by the actual contraction and movement.
Creep is increasing deformation under constant load. Stress relaxation is falling resistance at fixed displacement.
A neurodynamic test biases loading and may support mechanosensitivity when familiar symptoms change with a remote movement. Integrate the result with other findings.
Flexibility, Stretching Techniques, and Joint Range of Motion
When a joint is restricted, compare active and passive motion and consider symptoms, joint structure, muscle–tendon resistance, neural mechanosensitivity and motor control. The response to stretching depends on which factors limit the task and what the tissues can tolerate.
Neurophysiology of Stretching and Mechanoreceptor Reflexes
Muscle spindles and Golgi tendon organs provide complementary information about length and force. Their effects on motor output depend on the spinal circuits and the task.
Muscle spindle Golgi tendon organ
Length and length change Muscle–tendon tension
↓ ↓
Groups Ia and II Group Ib
↓ ↓
Stretch reflex and other Force feedback through
spinal pathways spinal interneurons
Muscle Spindle and Stretch Reflex
Spindles contain intrafusal fibers arranged in parallel with the force-producing extrafusal fibers. Primary Ia afferents respond to length and its rate of change. Secondary group II endings primarily signal length. Gamma motor neurons adjust spindle sensitivity by activating the polar parts of intrafusal fibers. A quick stretch can increase Ia discharge and excite alpha motor neurons of the same muscle through a monosynaptic connection. Ia input can also inhibit antagonist motor neurons through an interneuron. Voluntary movement can include co-contraction, depending on the task.
Golgi Tendon Organ and Force Feedback
Golgi tendon organs lie in series with groups of muscle fibers at muscle–tendon junctions. Ib afferents convey information about tension, especially during active force production. A classic spinal pathway includes inhibition of the same muscle through interneurons. Human studies also show that loading and locomotion can alter the response. This circuit does not establish how much a muscle will relax during a particular stretching technique.
Viscoelastic Properties of Connective Tissue
Muscle–tendon units and other connective tissues show elastic and time-dependent behavior. Stress is force per unit area. Strain is the change in length relative to the starting length.
Simplified tensile test
Increasing strain → Toe region → Steeper elastic region → Yield → Failure
Fiber crimp Mostly recoverable Damage accumulates
straightens strain below yield past yield
The diagram describes a simplified tensile test. In clinical stretching, a gain in measured range can reflect improved stretch tolerance or changes in resistance to motion. Deliberately loading beyond yield risks tissue injury.
- Creep: With constant stress or load, strain or elongation gradually increases.
- Stress relaxation: With strain or displacement held constant, stress or the resisting force gradually falls.
- Hysteresis: Part of the mechanical energy is dissipated during a loading and unloading cycle.
For example, a low-load device that maintains its force as a joint moves can illustrate creep. Holding a joint at the same angle while measured passive resistance falls illustrates stress relaxation. Check how the device behaves and reassess range, skin, comfort and irritability over time.
Stretching Modalities and Prescriptive Parameters
1. Static Stretching
Use a controlled hold at a tolerable sensation of stretch. For generally healthy adults, an ACSM flexibility example accumulates about 60 seconds per exercise on at least two days per week. Two comfortable 30-second hamstring holds are one way to reach 60 seconds. Clinical dosing depends on the tissue and symptoms. A study in adults aged 65 years or older found greater hamstring range gains with 60-second holds than with shorter holds in that protocol. The measured gains do not establish permanent tissue lengthening.
2. Dynamic and Ballistic Stretching
Dynamic stretching uses controlled repetitions through an available range, such as progressively larger walking lunges or arm swings during warm-up. Ballistic stretching uses momentum and can include bouncing near end range. Select speed and range for the patient's task and tolerance, particularly after injury. When the next task requires maximal force or speed, account for the duration of static stretching and the rest of the warm-up. In a study with a full dynamic warm-up, brief static stretching produced no measurable performance penalty for the tests used.
Proprioceptive Neuromuscular Facilitation (PNF) Stretching
Names and exact procedures vary. Describe the contraction and who moves the limb when documenting the technique.
| Technique | Typical sequence |
|---|---|
| Hold–relax | Position at a tolerable limit, ask for a brief submaximal isometric contraction of the restricted muscle, then have the patient release and guide the limb into available range. |
| Contract–relax | In a movement-based version, resist a controlled contraction with some movement, then allow release and guide a further stretch. Some studies use the term for an isometric precontraction. |
| Hold–relax with agonist contraction | Follow the isometric contraction and release with active contraction of the muscles that move the joint toward the intended range. |
For a hamstring example, support the thigh, ask for a brief gentle knee-flexion effort without motion, then allow relaxation. Ask for active knee extension to use the newly available range if that is the chosen variation. Reassess the range and symptoms. Adapt the effort and avoid a painful forceful contraction. Studies report changes in stretch tolerance and mechanical resistance. The spinal reflex models alone do not demonstrate the cause of a range gain or establish one version as universally superior.
Clinical Neurodynamics (Butler & Shacklock)
Joint movement can change a peripheral nerve's position and strain relative to surrounding tissues. Neurodynamic assessment asks whether a controlled movement reproduces familiar symptoms and whether changing load at a distant site changes those symptoms. Compare sides and integrate the finding with strength, sensation, reflexes and other tests. Sensations can also occur in people without symptoms.
Sliders and Tensioners
Slider Load one end while unloading the other, then reverse
Tensioner Increase load from both ends, then release
In experimental preparations, selected sliders produced more excursion and less strain than the paired tensioning techniques. The measured changes depend on the nerve and the technique. For an irritable presentation, assess first and use small, comfortable movements if a trial is appropriate. Progress according to the response. Check precautions and the operative plan after surgery.
Upper-Limb Neurodynamic Tests (ULNTs)
These tests bias loading across a region and are performed with controlled movement. The examples below follow the sequencing protocol reported by Schmid and colleagues (2009). Stop at the relevant symptom or planned limit and compare the response with the other side. A remote movement, such as changing cervical side bend during distal symptoms, can help interpret the response.
| Test | Main bias | Example sequence after initial positioning |
|---|---|---|
| ULNT1 | Median | Shoulder girdle fixation and abduction, wrist extension, supination, shoulder external rotation, elbow extension |
| ULNT2a | Median | Shoulder girdle depression, elbow extension, shoulder external rotation, supination, wrist extension, shoulder abduction |
| ULNT2b | Radial | Shoulder girdle depression, elbow extension, shoulder internal rotation, pronation, wrist flexion, shoulder abduction |
| ULNT3 | Ulnar | Wrist extension, pronation, elbow flexion, shoulder external rotation, shoulder girdle depression, shoulder abduction |
Lower-Limb Neurodynamic Tests
- Straight leg raise: In supine, flex the hip with the knee extended within tolerance. Note familiar leg symptoms and the position at which they occur. A controlled remote change such as ankle dorsiflexion can help explore mechanosensitivity when symptoms are proximal. Interpret the result alongside the neurologic examination.
- Slump: Add seated spinal and cervical flexion, knee extension and ankle dorsiflexion progressively as appropriate. If familiar posterior thigh or calf symptoms arise, keep the limb position and release cervical flexion. A change supports a mechanically sensitive neural component in context. Similar responses can occur in people without symptoms.
- Femoral stretch: In prone, flex the knee gently and assess whether familiar anterior thigh symptoms arise. Interpret with hip motion, local muscle symptoms and the neurologic examination. It can contribute to assessment of midlumbar nerve root involvement.
Which sequence describes a hold–relax stretch with an added agonist contraction to improve available knee extension?
Hold knee extension isometrically, then resist the hamstrings into further flexion
Ask for a brief isometric hamstring contraction, then release and ask the quadriceps to extend the knee into available range
Use a brisk passive bounce at end range, then have the patient flex the knee
Resist continuous knee flexion while the patient actively contracts both muscle groups
A low-load extension device maintains a constant tensile load during a measured trial. Passive extension increases gradually while the load stays the same. Which viscoelastic response does this illustrate?
Stress-relaxation
Hysteresis
Creep
Thixotropy
In a standardized upper-limb neurodynamic exam, which combination is characteristic of the radial-biased ULNT2b?
Shoulder external rotation, forearm supination and wrist extension
Shoulder external rotation, forearm pronation and terminal elbow flexion
Shoulder internal rotation, forearm supination and wrist extension
Shoulder internal rotation, forearm pronation and wrist flexion
The seated slump test reproduces familiar posterior thigh and calf symptoms with cervical flexion, knee extension and ankle dorsiflexion. Which maneuver helps assess whether a remote movement changes the response?
Release cervical flexion toward neutral while maintaining knee extension and ankle dorsiflexion
Immediately release the ankle dorsiflexion and record the test as unequivocally positive
Passively flex the hip to 90 degrees while having the patient rotate the trunk
Apply axial compressive pressure directly to the vertex of the patient's skull
Sections you finish are checked off in the contents.