Motor learning and PNF

Principles of motor learning/motor control

Definitions

Motor learning and motor control

Integrated concepts that encompass both the body’s intrinsic neuromuscular capabilities - relying on intact physiological systems - and external environmental factors that enhance an individual’s ability to execute movements accurately. The central nervous system relies on continuous input to learn and retain the ability to perform tasks.

Motor program

A sequence of movements or motor actions stored in the brain that are activated when performing specific tasks or motor skills.

Motor plan

The cognitive process involved in preparing and executing a movement.

Feedback

Information provided after a task is performed, regarding the accuracy of that performance.

Feedforward

Information provided before a task is performed, about how to prepare for the activity.

Strategies for motor learning

Motor learning strategies are required when attempting to learn a new skill through a combination of mass practice and experience. Specific strategies to assist an individual in learning a new skill are as follows:

• Practice skill
  • Early practice may use guided movement (the clinician passively moves the limb through the movement so the patient feels it) and mental practice or guided imagery (the patient rehearses the movement mentally without moving)
  • Practice initially uses a blocked schedule, progresses to a variable schedule, and finally progresses to a random schedule as repetitions increase and learning improves
  • Massed practice has fewer and shorter rest intervals between trials, while distributed practice spaces the repetitions with rest intervals between them
• Provide effective feedback
  • Begin with extrinsic (augmented) feedback from the clinician
  • Fade extrinsic feedback over time so the patient relies more on intrinsic feedback
    • The two types of extrinsic (augmented) feedback are knowledge of results and knowledge of performance
  • Types of feedback schedules
    • Feedback given after completion of every task (early stage of learning)
    • Summary feedback - feedback given after a set number of attempts
    • Fading feedback - decreasing the amount of feedback given to none, as appropriate
    • Bandwidth feedback - feedback only given if the movement is outside the designated range
• Transfer of skill
  • Skill acquisition leads to the skill being generalized and applied successfully in varied situations and environments
  • This occurs after the patient is deemed proficient in the original skill

Definitions

Blocked practice

Practice of a single motor skill repetitively.

Variable practice

Practice of variations of the same motor skill under changing conditions (e.g., different speeds, distances, or surfaces).

Random practice

Practice of a group of motor skills in no predictable order.

Intrinsic feedback

Internal sensory information used to correct oneself when performing a motor skill.

Extrinsic feedback

External sensory information used to correct the performance of a motor skill by an outside observer.

Knowledge of results

Augmented feedback about the outcome of movement (understanding the goal).

Knowledge of performance

Augmented feedback about the characteristics of the movement performed (understanding the process of attaining a goal).

Stages of motor learning

Motor skill acquisition follows three stages.

• Cognitive - “What to do” stage
  • Learner develops an understanding of the task and how to perform it
  • Movements are slow and inconsistent, with an increased amount of trial and error
    • Extrinsic feedback only
    • Blocked scheduling
    • Consistent feedback after each trial of movement
• Associative - “How to do” stage
  • Learner practices and refines movement
  • Learner begins to understand errors of movement
    • 50% extrinsic feedback and 50% intrinsic feedback
    • Continue with blocked scheduling, progressing to variable scheduling as skill acquisition occurs
    • Feedback should progress from summary to faded, or decreasing, over time
• Autonomous - “How to succeed” stage
  • Skills performed automatically and with minimal conscious error
  • Highly skilled and consistent performance
    • Intrinsic feedback only
    • Random practice schedule
    • If any feedback is given, it is bandwidth feedback

Task-specific training

Definitions

Task-specific training

A treatment approach with the goal of promoting recovery of motor function to baseline after injury due to a central nervous system insult. The involved segments are the target of practice.

Examples of task-specific training

• Locomotor training
  • Motorized treadmill training with partial body weight support to promote early gait training
  • This activity is tailored to the patient’s current functional status to help them return to baseline
• Constraint-induced movement therapy (CIMT)
  • Utilized post-stroke to constrain the unaffected upper extremity by use of a protective hand mitt
    • The goal is to constrain the unaffected extremity and force the use of the affected limb
• Mirror therapy
  • The patient moves the unaffected limb while watching its reflection in a mirror, which creates the illusion of normal movement in the affected limb; it is used to improve movement after stroke

Bridging

Bridging is lifting the pelvis off the mat from hook-lying (knees bent, feet flat), working the hip and trunk extensors. After a stroke, or an incomplete spinal cord injury with working hip extensors, it is an early bed-mobility skill (scooting, placing a bedpan, preparing to roll and sit up) and a pre-gait activity that trains the hip extension and pelvic control needed in stance; after a stroke, the patient is cued to bear weight evenly through the affected leg. It treats weakness and trunk control, not visual or attention deficits such as neglect.

Proprioceptive neuromuscular facilitation (PNF)

Definitions

Proprioceptive neuromuscular facilitation (PNF)

An approach that uses spiral and diagonal movement patterns, which combine motions outside typical synergy patterns, to facilitate mobility, stability, and strength. PNF uses procedures such as quick stretch, resistance, irradiation (overflow), manual contacts, approximation, and traction.

PNF techniques can be broken down into the following categories.

Rhythmic initiation

• A progression of movement from passive → active-assisted → active → resisted. This technique is used to improve the initiation and coordination of movement.
• Example:
  • Patient: A person with Parkinson’s disease.
  • Application: The therapist helps initiate movement for rolling from supine to side-lying, gradually allowing the patient to take over the movement and eventually providing resistance for strengthening.

The table below summarizes the remaining PNF techniques using the same pattern: the therapist applies the technique to address a specific movement or stability deficit.

Technique	Description	Example application
Rhythmic rotation	Slow, passive rotational movement around a longitudinal axis to reduce hypertonia and promote relaxation	Slowly rotating the trunk of a patient with trunk spasticity before trunk flexion activities
Rhythmic stabilization	Isometric contractions of antagonist muscle groups simultaneously to improve joint stability and postural control	Applying multidirectional resistance to the shoulders of a patient sitting unsupported
Approximation	Gentle joint compression, typically in weight-bearing positions, to stimulate mechanoreceptors and enhance postural stability and muscle activation	Compressing the shoulder joints of a patient in quadruped or standing to promote co-contraction
Slow reversals	Alternating concentric contractions of agonist and antagonist muscles without relaxation to improve coordination and smooth transitions	Alternately resisting knee flexion and extension in a seated patient with knee weakness
Hold-relax	Isometric contraction of a muscle group followed by relaxation and passive stretching to improve range of motion	Isometric hamstring contraction against resistance followed by passive stretching for hamstring tightness
Contract-relax	Isotonic contraction through the available range, followed by relaxation and passive movement into an increased range	Resisting hip extension, then relaxing to allow the therapist to stretch into greater hip range of motion
Repeated contractions	Repeated quick stretches followed by resisted contractions to enhance the initiation and strength of weak muscles	A quick stretch to the anterior deltoid followed by resistance to strengthen shoulder flexion

PNF patterns describe the way in which the joints move to perform specific movements outside of synergy. PNF patterns exist for both the upper and lower extremities. The following are the patterns for the upper extremity:

D1 flexion

• Shoulder: flexion, adduction, external rotation
• Forearm: supination
• Wrist: radial deviation, flexion
• Finger: flexion

D2 flexion

• Shoulder: flexion, abduction, external rotation
• Forearm: supination
• Wrist: radial deviation, extension
• Finger: extension

D1 extension

• Shoulder: extension, abduction, internal rotation
• Forearm: pronation
• Wrist: ulnar deviation, extension
• Finger: extension

D2 extension

• Shoulder: extension, adduction, internal rotation
• Forearm: pronation
• Wrist: ulnar deviation, flexion
• Finger: flexion

The following are the patterns for the lower extremity:

D1 flexion

• Hip: flexion, adduction, and external rotation
• Ankle: dorsiflexion and inversion
• Toe: extension

D2 flexion

• Hip: flexion, abduction, and internal rotation
• Ankle: dorsiflexion and eversion
• Toe: extension

D1 extension

• Hip: extension, abduction, and internal rotation
• Ankle: plantar flexion, eversion
• Toe: flexion

D2 extension

• Hip: extension, adduction, external rotation
• Ankle: plantar flexion, inversion
• Toe: flexion

Exam tip: signs to stop an intervention

The PTA carries out the established plan of care but must recognize when a patient’s response means an activity should stop rather than continue. Discontinue the activity and notify the supervising PT if you see:

• An abnormal vital sign response (e.g., excessive change in heart rate or blood pressure, oxygen desaturation)
• Signs of autonomic dysreflexia (pounding headache, flushing, sudden hypertension) in a patient with a spinal cord injury - an emergency: first sit the patient upright with the legs lowered, loosen tight clothing, and call for help
• Orthostatic symptoms (lightheadedness, pallor, diaphoresis) during body-weight-supported treadmill training
• Excessive fatigue, pain, or loss of postural control beyond what the activity is meant to challenge