1.1: Strength, Reflexes, and Flexibility

Key Points

1. In persons with damaged nervous systems, these tests may be context-dependent.
2. It is important to test and retest in the same environment and in test positions.
3. Recognize that the results of these tests may not automatically translate into what you might predict a patient's performance will be during a functional activity.

General Considerations

Safety

Although the therapist is assessing the musculoskeletal system, in a patient with neurologic dysfunction, cognitive issues resulting in a decreased awareness of overall safety must be considered. In addition, in the presence of weakness or sensory loss, body alignment and joint protection is often one of the therapist's most important tasks. Providing external stability through manual contacts and support from the sitting surface will not only protect the patient, but also allow for the most reliable results of the tests.

Posture and Positioning

Posture and alignment of body segments, must not be overlooked in the individual with neurologic dysfunction. In order to function effectively and efficiently, the human body must be able to respond to changes in gravity secondary to alterations in the alignment of body segments.

The therapist needs to consider:

• Both movement and the relationship between how the muscles are functioning and the patient's biomechanical alignment.
• The initial postural alignment of the patient before movement.
• The alignment of body segments throughout the movement.

Motor Control

The control of a patient's movement is often more critical to consider than his or her ability to produce force. For example, in a patient with a cerebellar lesion, strength will be typically be intact, however functional activities that involve the coordination of this strength may have significant deficits. The therapist needs to consider:

• The muscles used to complete the desired movement.
• The patient's ability to relax antagonists allowing the agonists to contract effectively.
• The velocity and acceleration of movements desired to efficiently complete the task.
• Compensations in other body segments.

Range of Motion

Use care when performing of joint range of motion (ROM) tests and activities in the presence of spasticity or flaccidity. Spasticity may interfere wit h range measurement because it may change depending on the relationship of the trunk or extremity to gravity, therapists' hand positions and technique.

Instructions to the patient: Make sure that your commands to the patient are consistent wit h the type of ROM you are assessing (or performing as a treatment intervention). Some examples of instructions follow:

• Passive: "Relax and let me move you."
• Active Assisted: "I want you to try to move through the motion and I will help you if you need assistance." When you ask the person to try to move, but there is no movement noted, this will still be considered active-assisted not passive, because of the commands given. Documentation should reflect this distinct difference. For example, a therapist may document: "Active Assisted ROM was attempted, but no motion noted."
• Active: "I want to you to move through the motion as far as you can."
• Hand placement: The technique used while performing ROM may promote hyperactivity in the muscle being elongated. Examples include: During ROM at the ankle, a hand on the ball of the foot may produce hyperactivity in the gastrocnemiussoleus and prevent full movement into dorsiflexion; during wrist extension, palmar contact may promote finger and wrist flexion limiting elongation of the long finger flexors.
• Speed of technique: The speed of the technique may produce spasticity -- the faster the movement the more likely the muscles are to respond wit h involuntary contraction (see tone below)
• Protecting the joints: In the presence of flaccidity care must be taken, as the joints have no protection from the normal reaction of muscles to stretch. Overstretching of joint structures may occur. The shoulder is particular vulnerable. Remember to always have one hand on the scapula when performing ROM.

Flexibility

Individuals with neurologic impairment generally demonstrate deficits in voluntary movement, whether secondary to muscle weakness/imbalance, spasticity, or posturing. Alterations in muscle tone secondary to neurologic insult may lead to changes in the muscle properties itself. These changes in the architecture of 4 the muscle cause a reduction in the flexibility of the muscle, or the ability of the muscle to lengthen appropriately.

As with testing joint ROM or flexibility in a person with a neurologic injury, remember to move the limb slowly to avoid eliciting spasticity that may reduce accuracy of your tests. The following body parts/segments that are important to assess are listed below, each wit h a particular critical aspect of functioning that requires that particular flexibility.

• Cervical flexibility in all planes of movement for head righting and equilibrium reactions
• Pectoral muscle length for posture and balance
• External rotators of shoulders and supination of forearms for upper extremity support in the absence of triceps
• Wrist extensors for upper extremity support
• Trunk elongation for general posture, balance, and mobility
• Hip flexors for prone assumption and gait
• Hamstring length for upright activities and gait
• Hip adductor length for ADLs and hygiene, as well as general mobility
• Hip external rotation with hip flexion for dressing
• Hip internal rotators for scooting and gait
• Plantarflexor length for gait and balance reactions

Reflexes

Examination of the deep tendon reflex (DTR) is an unconscious motor response to a sensory stimulus. It gives information about the location of the neurologic lesion by assessment of the reflex arc. Performance of this test requires a reflex hammer to provide stimulation of sensory receptors (the muscle spindle), which evokes action potentials that are conducted into spinal cord. The sensory neuron synapses with an association neuron, which synapses with somatic motor neuron, which conducts impulses to muscle and stimulates a reflex contraction. Remember that the brain is not directly involved.

Interactive Element

Complete the chart in preparation for practicing MMT skills

Exercise \(\PageIndex{1}\)

For each of the muscles and activities listed above, role play as if you lack significant flexibility and then try to perform the associated activity to experience the difficulty in movement

• Hyperactive tendon responses suggest lesions of the UMN, (corticospinal tracts).
• Pendular tendon reflexes are suggestive of cerebellar (Cb) dysfunction.
• Absent tendon reflexes suggest LMN lesions. (Compare with decreased responses in an orthopedic evaluation.)

Examination may include any or all of the following reflexes, each representing a particular myotome, which is the group of muscles a specific nerve root(s): (There are videos for reflex testing and other testing on www.neuroexam.com…it is open access, but you cannot download the videos. We could insert the link for now and maybe we take our own later)

• Achilles tendon (S1,S2)
• Biceps (C5, C6)
• Brachioradialis (C6)
• Quadriceps (L3, L4)
• Triceps (C7)

Strength

Manual muscle tests (MMT) are used to evaluate strength and can be misleading in the neurologically impaired individual. These individuals certainly have weakness, but it is a more complex phenomenon than weakness that results from the patients with intact nervous systems. Lesions of the upper motor neuron affect the number, type and discharge frequency of motor units recruited during performance. Even if there is minimal or no loss of crosssectional area in the muscle fibers, force generation is impaired. Over time, secondary changes can also occur in muscle with selective atrophy of fast twitch fibers.

• The nervous system adopts a variety of synergistic muscle activation patterns to control the body's degrees of freedom, or available planes of movement. A neurologically impaired person often has less control and fewer synergistic patterns are available. This makes it difficult for an individual to isolate a muscle or muscle group for a reliable manual muscle test. The opposite also holds true that individuals unable to isolate a muscle contraction as required for a muscle strength test, might exhibit good force production in a gross or mass synergy pattern.

Figure \(\PageIndex{1}\)

• Results of strength testing on a person with an upper motor neuron lesion cannot be reliably interpreted without knowing details of the testing procedure. Even then, the test results may not tell you what the person is capable of doing functionally.
• The muscle itself may be capable of producing force, but the strength may test lower secondary to recruitment problems, problems of co-contraction, timing of contractions or sequence of firing of muscles involved in the motor plan.
• An individual might produce a grade 0 or 1 on an isolated movement test but perform at a 3/5 or better on a task where it acts synergistically with others. This is an example of strength or force production being task specific.
• This weakness might not be improved by specific exercises to strengthen the muscle.

Clinical Tips:

• As a rule of thumb, muscle testing is only valuable if the patient is able to produce an isolated muscle contraction.
• Documentation for motor ability, if MMT grades are not appropriate, should qualitatively describe the percentage or fraction of movement throughout the range of motion being tested.