Lecture 7 - Coordination and Balance Flashcards
What is coordination
- The ability to execute smooth, accurate, controlled movement
- coordinated movement involves multiple joints and muscles that are activated at the appropriate time with the correct amounts of force so that tooth, efficient and accurate movements occur
- essential in sequencing, timing, and grading
Dexterity
Skillful use of the fingers during fine motor tasks
Agility
ability to readily and smoothly initiate, stop, or modify movements while maintaining postural control
Center of mass (COM)
The midpoint of the body mass; in erect standing posture, the COM is located at the level of the second sacral segment
Base of support (BOS)
Refers to the area beneath a person that includes every point of contact that the person makes with the supporting surface
Balance
The condition in which all the forces acting on the body are balanced such that the centre of mass (COM) is within the stability limits, the boundaries of the base of support (BOS)
Sensory integration into postural control
- The sensory system provide the CNS with important information about postural control and balance, including information about the results of our own actions and the surrounding environment
- Includes vision, somatosensory, and vestibular
Visual system
The visual system serves as an important source of information for the ability to perceive movements and detect the relative orientation of body segment sand orientation of the body in space (visual proprioception)
Focal vision
- Cognitive/ explicit
- plays a major role in localizing feature in the environment and in our conscious reaction to visual events
Ambient vision
- Sensorimotor/implicit
- Utilizes the entire visual field to provide information on the location;izing features about the environment and to guide movements using largely nonconscious awareness
Optic ataxia
The patient can recognize an object using focal vision but cannot use visual information to accurately guide the hand to the object (impaired ambient vision)
Visual agnosia
The patient cannot recognize common objects, but can use ambient visual system to reach and grasp an object or navigate an environment
Somatosensory system
inputs include the cutaneous and pressure sensations from the body segments in contact with the support surface and muscle and joint proprioception throughout the body
Example of a somatosensory system
Light touch contact from the hands on a stable surface is also used as a balance aid, provides information about the relative orientation and movement of the body in relation to the support surface
Vestibular system
- Stabilizes gaze during head movements via the vestibulo-ocular reflex (VOR)
- Assists in the regulation of postural tone and postural muscle activation via the vestibule-spinal reflex (VSR)
Semicircular canals (SCC)
Detects angular acceleration and deceleration forces acting on the head and are sensitive to fast (phasic) movements of the head
Otolith organs
Detect linear acceleration and orientation of the head with reference to gravity and response to slow head movements and positional chance referenced to gravity
Peripheral motor system
Somatice Motor System includes muscles, joints, and their sensory and motor innervation
Central motor system
- Divided into three hierarchical levels
- This does not imply a strictly top-down control of coordinated movement as each level of the nervous system can influence other levels depending on task demands
Highest level of the central motor system
Structures: associated areas of the neocortex and basal ganglia of the forebrain
Functions: strategy - the goal of the movement and the movement strategy that best achieves the goal
Middle level of the central motor system
Strucutres: motor cortex and cerebellum
Function: tactics - the sequence of muscle contractions, arranges in space and time, required to smoothly and accurately achieve this strategic goal
Lowest level of the central motor system
Structures: brain stem and spinal cord
Function: execution - activation of the motor neuron and interneuron pools that generate the goal-directed movement and make any necessary adjustments of posture
Cerebellum
- The primary function of the cerebellum is regulation of movement, postural control, and muscle tone
- Compares the commands for the intended movement transmitted from the motor cortex with the actual motor performance of the body segment
Cerebellar pathology
Many of these impairments either directly or indirectly influence the patient’s ability to execute accurate, s smooth, controlled movements
- The motor deficits identified emphasize the crucial influence of the cerebellum on equilibrium, posture, muscle tone, and initiation and force of movement
Basal ganglia
- The basal ganglia are a group of uncle located at the base of the cerebral cortex
- The three main nuclei of the basal ganglia are the caudate, putamen, and the globes pallidus
Basal ganglia pathology
Patients with lesions of the basal ganglia typically demonstrate several characteristic motor deficits
1. slowness of movement
2. involuntary, extraneous movement
3. alterations in posture and muscle tone
Dorsal column-medial lemniscal pathway
- Regulation of movement is dependent on sensory afferent information
- It mediates sensations critical to coordination movement such as proprioception, kinaesthesia, and discriminative touch
Dorsal column- medial lemniscal pathology
- Lack of joint position sense and awareness of movement, and impaired localization touch sensation
- Gait pattern is usually wide-based and swaying, with uneven step lengths and excessive lateral displacement
- dysmetria
- coordination and/or balance problems will be exaggerated when vision is occluded or when the patient’s eyes are closed
Dysdiadochokinesia
- an impaired ability to perform rapid alternating movements
- this deficit is observed in movements such as rapid alternation between pronation and supination of the forearm
Hypotonia
- A decrease in muscle tone
- It is believed to be related to the disruption of afferent input Fromm stretch receptors and/or lack of the cerebellum’s efferent influence on the fusimotor system
Dysmetria
- An inability to judge the distance or range of movement
- It may be manifested by an overestimation (hypermetria) or underestimation (hypometria) of the required range needed to reach an object or goal
Dyssynergia
- Describes a movement performed in a sequence of component parts rather than as a single smooth activity
- For example, when asked to touch the index finger to the nose, the patient might first flex the elbow and then adjust the position of the wrist and fingers, further flex the elbow and then finally flex the shoulder
Rebound phenomenon
- The loss of the check reflex or check factor, which functions to halt forceful active movements when resistance is eliminated
- When application of resistance to an isometric contraction is suddenly removed, the limb will remain in approximately the same position by action of the opposing muscle
Tremor
- An involuntary oscillatory movement resulting from contractions of opposing muscles
- An intension tremor occurs during voluntary motion of a limb and tends to increase as the limb nears its intended goal or speed is increased
Postural (static) tremor may be evident by back-and-forth oscillatory movements of the body while the patient maintains a standing posture
Assessment of coordination - finger to finger test
Procedure: patient attempts to touch the index finger of the examiner with an outstretched arm
- A fast response is encourages as the examiner’s arm is moved horizontally
Positive: delay in movement initiation, terminal tremor - due to alternating contractions of agonist and antagonist. and dysmetria - inaccurate amplitude, impaired timing of muscle force
Assessment of coordination - heel-to-shin
Procedure: Patent lies supine and places heel on the think of the other leg near knee and slide the heel down the shin towards the foot
Positive: dysmetria - difficulty placing the heel. Dyssynergia - method of getting the heel to shin (flexing hip and knee in sequence rather than in one synergistic movement
Assessment of coordination - rebound test
Procedure: patient performs an isometric contraction of the elbow flexors, examiner initially resists force, then releases
Positive: patient cannot stop movement once resistance is removed or rebound phenomenon - problem with braking of movement
Assessment of coordination: rapid alternating movements
Procedure: patient puts hand on a hard surface, and alternates between palm up and palm down
Positive: movement is performed slowly and with exaggerated supination and pronation or disdiadochokinesia - difficulty performing rapid alternating movements
Ankle strategy
- shifting the COM forward and back moving the body as a relative fixed pendulum about the ankle joints
- muscles are activated distal-to-proximal sequence
- The ankle strategy when sway frequencies are low and disturbances of the OCM are small and well within the LOS
- With forward sway, goastroc is activated first, then hamstrings, then paraspinal muscles
- with backwards sway, the anterior tibialis is activated first, followed by quads, then abdominals
Hip strategy
- Shifts the COM by flexing or extending the hip
- it has a proximal pattern of muscle activation before distal activation
- With forward sway abdominals are activated first, followed by quadriceps
With backward sway, paraspinal muscles are activated first, followed by hamstrings. Hip strategies provide primary control for mediolateral stability - hip abductors and adductors are involved in lateral sway control
- recruited with faster sway frequencies and larger disturbances of the COM or when support surface is small
Stepping strategy
Realigns the BOS under the COM by using rapid steps or hops in the direction of the displacing force, for example stepping forward or backwards
- in instances of lateral destabilization, the individual takes a side step or a cross step to bring the BOS back under the COM
- typically recruited in response to fast, large postural perturbations when ankle and hip strategies are not adequate
Seated control
- During quiet sitting, the degree and direction of the sway should be determined
- grasp strategies (holding onto the edge of the seat) or lower extremity hooking strategies ( the foot and leg around the platform mat leg) are common strategies in the presence of significant instability
Standing control
- Weakness and limited ROM in the ankles will influence successful use of an ankle strategy, whereas weakness and limited ROM about the hips will influence the hip strategy
Anticipatory postural control
- Anticipatory postural control, the ability to activate postural adjustments in advance of destabilizing voluntary movements, should be examined
- For example, the therapist asks the patient while standing or sitting to raise both arms above head or catch a weighted ball
Dual-task control
- This is the ability to perform a secondary task (motor or cognitive) while maintaining standing or seated control
- For example, while standing the patient is asked to count backward from 100 by 7 (simultaneous verbal0cognitive task) or pour water into a glass (secondary motor task)
Romberg test
- The Romberg test is historically one of the oldest sensory tests for postural control
- During the test, the patient is instructed to stand with feet together, eyes open (EO) unaided for 20 to 30 seconds
- If the patient demonstrates significant sway or instability with EO, the test is over
- the patient is then asked to stand with eyes closed (EC)
The test is negative, if there is no change or only minimal worsening with EC
The functional reach test
- was cerated to measure the limbs of stability of individuals while reaching forward in a standing position
- the limits of stability is defined as the maximum distance that the COM can be moved safely without changes in the base of support
- Functional reach of stability is defined as the maximum distance one can reach forward beyond arm’s length while maintaining a fixed base of support in the standing position
