Multiple factors in control of occupational performance skills

The execution of skills is seen in movements which are the outcome of the integration of muscular and neural components of motor control interacting with psychological, social and environmental factors. Consider how a person gets out of bed in the morning. This is not only the result of bio-mechanical and neurological activity. The quality, speed and precise nature of the movements produced will vary according to circumstances. Hence, if the person has overslept and is late for work, his movements will be hurried and less well controlled. If getting up and not wanting to disturb a sleeping partner, movements may be slow and cautious. In terms of the physical environment, the precise performance of this skill will vary with the qualities of the bed and its relationship to the floor and other objects in the room. A soft, low bed will require different qualities and degrees of movement to get out of, compared with a high, firm bed. Such examples demonstrate the multiple factors that determine the characteristics of this performance and skilled movements.

In the hierarchical model of motor control presented in previous chapters, the motor commands issued at the highest levels of the central nervous system drive the activity in the subcortical, brain stem and spinal motor areas in top-down processing. When psychological and social factors of task performance are included, the motor system needs to be viewed functionally as a series of interconnected centres that work in series and in parallel and feature numerous feedback and feedforward circuits. The focus for control of movement is thought to shift between these centres, depending on the needs and demands of a given performnace, and the environmental conditions experienced at the time. The cognitive system is a major component of the motor control of movement, particularly when decision making and problem solving are involved.

In organising and producing movement, the brain regulates posture to ensure that the body can maintain and restore equilibrium and be safe from the threat of harm. For example, when reaching for an object, if the line of gravity begins to move beyond the base of support, compensatory adjustments are made to maintain equilibrium. If these adjustments are not made, the intended goal is abandoned as righting and saving reactions are initiated. Another priority is the adoption of body positions that allow any given task to be carried out in the most efficient way possible.

Consider the skills of crossing one of the moving walkways found at fairgrounds. The priority in movement is directed to the negotiation of the walkway. The attention is fully engaged in the task of keeping upright while walking. The simultaneous execution of other activities, such as talking or reading signs, becomes impossible, whereas these would pose no difficulties when walking along a clear, level corridor.

To interact effectively with the environment, the body uses a number of basic, or core, positions. From these positions, a sequence of movement patterns is carried out to move from one position to another, and to orientate the body in a stable position for the performance of occupations.

The objectives guiding the selection of these positions are:

to position the head for optimal visual and auditory monitoring of events;
to bring the trunk and upper limbs into the most effective and efficient position for the execution of skills;
to ensure optimal stability and equilibrium;
to minimise the amount of physical effort required performances;
to execute skills and achieve
to achieve human occupation.

The core positions are lying, sitting, squatting and standing. The choice of the position to be adopted for skill performance depends on the attributes of the skill and the environment. An understanding of the performance demands and the priorities for stability in these positions and movements leads to the identification of abnormalities in movement and the facilitation of effective performance.

Emotional and cognitive factors

Skill performance is orientated towards the achievement of a goal. A person’s ability to reach the goal is determined by their mood at the time and by their ability to organise and use stored knowledge about the movements involved and the environment. The ways in which emotional and cognitive factors affect movement will now be considered.

Emotional factors have been shown to have a significant effect on movement performance. Studies of human responses to stress have established that links exist between psychological state and physiological functioning. Neural connections between areas of the brain that apparently serve disparate functions suggest the potential for psychological factors to influence motor behaviour. The reverse, that physical activity can influence psychological state, is well accepted. The ability of physical exercise to stimulate the release of endorphins in the brain (neurotransmitters with some of the properties of opiates) has been established, and physical practices such as relaxation and breathing exercises are used in the treatment of some mental illnesses. Stress, or more specifically distress, is known to be a risk factor in the development of some physical conditions such as high blood pressure, heart disease and stroke. How then do psychological factors influence motor behaviour?

In previous chapters we have seen how sensory inputs are relayed to many areas, cortical and subcortical, and are used to provide knowledge to an individual in relation to the world, and to formulate appropriate actions and behaviours. The prefrontal areas of the frontal lobe interact with cortical areas in which meaning and significance are attached to the information received. These areas are also richly connected to the network of fibres and nuclei that form the limbic system (Figure 13.1). Hence connections exist that permit the attribution of emotional value to experiences, and emotional influences upon behaviour.

The limbic system also projects fibres to the hypothalamus and is influential in determining the relative balance of autonomic activity within the body. Thus there are two ways in which emotion may influence motor activity. One is its contribution at the conscious level, to decision making, motor planning and the execution of voluntary movements. The other is its influence upon skeletal muscle tone through up- or down-regulation of central nervous system activity, depending how stressed or at ease an individual is.

Reflective task

Think about an occasion when you have seen a friend really angry. On a piece of paper, write a list of all the things you saw that conveyed that mood. Everything in your friend’s behaviour will be the result of muscle activity.
Think about yourself when you are happy and relaxed, and when you are angry. What are the differences in your speech, facial expressions, gestures and body movements between these two states?

Figure 13.1 Connections between the limbic system, hypothalamus and prefrontal cortex.

Cognition is a complex system of interrelated parts that allows people to organise and use knowledge about themselves and the changing environment to achieve goals. The output of cognitive processing may be action, decision making or storage of information for future use. In the effective performance of all occupations, the sensorimotor system interacts with the cognitive system. There are many components of the cognitive system.

Perception is the component of cognition that makes sense of the environment by integrating all the sensory input to the nervous system for meaning. Visual, auditory and tactile input is processed for the recognition of objects and tools. The perception of the position of all the parts of the body in space, known as body scheme, is based on information from proprioceptors in the muscles and the joints. Body scheme must be integrated with visual and spatial perception of objects to perform the accurate movements of reaching and grasping.

Attention is another component of cognition. In task performance, an object or a tool is grasped, and attention must first be focused on it during perceptual processing for recognition. Selective attention allows any distracting noise in the environment, for example people talking in the same room, to be ignored. Attention must then be sustained long enough until the task has been completed. It is also possible to divide one’s attention, for example talk to a friend while doing the task.

Memory is the stored knowledge of objects, faces, environmental landmarks, movements and experiences. When an activity is performed, motor programmes, stored in procedural memory, are activated by the environment or from decision making. Stored motor programmes allow people to plan movements and to execute the correct sequence of actions. Orientation in time is based on prospective memory of when actions must be performed in the future. Everyday routine actions are mostly automatic, but prospective memory is required for non-routine actions that have to be remembered once in a while, for example phoning a friend on her birthday. Autobiographical memory of past experiences gives someone a personal identity and self-esteem. Shared experiences are important parts of interactions with family and friends.

The highest level of cognitive processes is the executive functions that allow people to set realistic goals and to modify movements and behaviour when conditions change. Tasks can be initiated and a judgement on the performance made at the end. Executive functions are important when people are confronted with an unfamiliar situation and flexible problem solving is needed to complete a task.

Reflective task

Walk round your local supermarket selecting the items you need from the shelves. Think about examples of all the components of perception and cognition that are basic to shopping: attention; visuospatial perception and body scheme; visual and verbal recognition; memory; executive functions. Evaluate the outcome when you unload your shopping at home.

Many areas of the cerebral cortex are implicated in cognition. The visual processing in the occipital lobe is an important part of visual perception. The parietal lobe processes tactile and spatial perception, body scheme and attention. The brain areas involved in memory include the temporal lobe for recent and spatial memory, the thalamus and hypothalamus for procedural memory; and the frontal lobes for prospective and autobiographical memory.

Figure 13.2 outlines the serial and parallel processing between the sensorimotor, cognitive, limbic and subcortical (basal ganglia and cerebellum) systems for the output to the muscles in motor behaviour.

Practice note-pad 13A: perceptual and cognitive impairments

Perceptual and cognitive deficits, which can significantly restrict movement, occur in many neurological conditions, especially stroke and traumatic brain injury. The problems relate to the component of the cognitive system that is impaired:

attention: inactivity due to poor arousal, distractions interrupt movement; failure to complete a task;
visual and spatial perception: poor object and/or face recognition (agnosia), under- or over-reaching; difficulty in finding the way round rooms and buildings and in the street;
memory: poor orientation in time; loss of self-Identity; procedural memory is usually spared;
executive functions: poor motor planning and initiation, movement stops when a new situation arises; unable to judge the effectiveness of movements.

Figure 13.2 Serial and parallel processing in the sensory, motor, limbic and cognitive systems in the control of movement.

Core positions and patterns of occupational performance skills

The core positions and movement patterns that are fundamental to all movements will now be considered in four sections: (i) lying, rolling and sitting up; (ii) sitting; standing and squatting; (iii) walking, and stair ascent and descent; and (iv) reaching and retrieving.

Framework for the analysis of movements

A systematic approach to the analysis of movements enables clear identification of any limitations imposed by musculoskeletal, neurological and cognitive deficits. This can form part of a broader analysis of any task performance. The components of the movement analysis are as follows:

occupational relevance and context;
description of the starting position;
breakdown of the movements into sequential stages;
description of any postural adjustments within each stage, followed by the movements of the limbs, starting proximally and moving distally. Multijoint movements are identified;
consideration of the cognitive and emotional factors that relate to the specific movement.

The ability to formulate movement analysis leads to an implicit understanding of a client’s movement problems.

Lying, rolling and sitting up

Lying down is the position of rest and sleep. It is a position that renders the person vulnerable, as neither vigilance nor rapid movement is easy when lying down, and is most often adopted in privacy. There are exceptions such as sunbathing, giving blood or receiving a massage, but in such activities the person does not have to be active. Some of the few activities performed in the lying position that have biological and interpersonal significance are those concerning sexual behaviour.

Lying is the most stable body position because the largest possible surface area of the body is in contact with a supporting surface, the bed or the floor. Side lying, which allows free movement of the upper limb and the pectoral girdle on the uppermost side, is the preferred position for reaching movements from lying. Side lying is also the optimum starting position for sitting up from lying, when the hand of the uppermost limb pushes on the bed to lift the trunk to the upright position.

Rolling is a sequence of movements to change from one lying position to another. It can also be a component in the process of moving from lying to sitting and the reverse.

There is considerable variability between individuals in the way in which rolling is performed. This can be seen by observing a group of people rolling over on the floor. In changing from supine to side lying, some initiate from the shoulders, others from the legs. Some raise the arms above the head during the roll. As the body rolls into prone lying, the head must be lifted by extension of the neck to keep the face clear of the ground. In all rolling movements, muscle tone is important to hold the body segments in alignment. The trunk must act as a rigid tube while the limbs are used to generate force for movement and then positioned to stabilise the body. The following exercise demonstrates rolling initiated by the lower limbs.

Reflective task

Working with a partner, one person lies on the floor, the other kneels down level with the pelvis. The person lying down must first keep the body completely relaxed while the kneeling person tries to roll him or her by lifting one side of the pelvis. Now the supine person should flex one hip and knee to bring the foot flat on the floor and at the same time consciously increase muscle tension throughout the body. The kneeling person starts to lift the pelvis again. Note how much more easily the supine body can now be rolled.

The properties of the supporting surface determine the effort needed. A soft, conforming surface offers limited stability and little resistance for the generation of momentum. Bedcovers may need to be considered as heavy layers hinder movement. Some people may need persuading to change from traditional sheets and blankets to a lighter duvet.

The movement from lying to sitting takes the person from a position of rest to a position preparatory for activity. Without it, a person cannot commence purposeful activity or interact effectively with the environment. This movement sequence, together with moving between sitting and standing, is a prerequisite for independence in basic self-care tasks, mobility and hence all occupations.

To sit up in bed, co-ordinated and simultaneous actions of the head, trunk and all four limbs are required. In moving from lying to sitting on the side of the bed prior to standing, the upper limbs drive the movement and lower limb activity varies according to how the person is lying at the start.

To move from side lying to side sitting the uppermost arm pushes down on the bed to start to lift the head and trunk. With sufficient clearance, the opposite arm can be positioned to take the weight of the trunk and then push down to raise the trunk further by stabilising the pectoral girdle and extending the elbow. The momentum generated, together with lateral flexion of the trunk on the side of the original uppermost arm, brings the head and trunk to the vertical. As the pelvis comes to the vertical the legs fall into a parallel position over the side of the bed with the knees flexed and the feet on the floor (Figure 13.3).

Reflective task

Practise the movement sequence from side lying to sitting on a plinth or a bed several times. Stop at certain points and feel which muscles are working. Refer to pushing movements of the shoulder in Chapter 5 and of lateral flexion of the trunk in Chapter 10. Repeat for the return movement from sitting to lying.

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