Extensive resources have been developed to support the application of the biomechanical model. Information about these resources exists in a wide variety of published sources, including those that focus on particular kinds of muscu-loskeletal impairments. While many of the resources for application are generic and can be applied across a wide range of client problems, there are also protocols or approaches that
are tied to a particular impairment (e.g., spinal cord injury or arthritis). Because different impair-ments mean different underlying causes for movement problems (e.g., de-innervation versus joint deterioration), the implications for what kinds of interventions to use and how to sequence them are different. Moreover, different impair-ments have different prognoses or expected outcomes that may call for a different balance of preventative, restorative, and compensatory approaches to intervention.
Assessment
Range of motion is one of the most basic meas-urements done in the biomechanical model. If the client is not capable of moving a joint volun-tarily (active range of motion), the therapist passively moves it to evaluate available range (passive range of motion). Flinn, Trombly Latham, and Robinson Podolsky (2008) recom-mend first doing a functional evaluation of active range of motion that involves asking the client to move various body parts. If observation reveals no obvious limitations that would restrict functional performance, no further evaluation of range of motion is done. However, if problems are noted, then a more detailed range of motion evaluation is completed.
Range of motion is measured in degrees of movement about the axis of a joint. One of the oldest and most common ways of measuring range of motion is with a goniometer, an instru-ment with a protractor, axis, and two arms that is placed over the joint and aligned with the bones that move about the joint’s axis to meas-ure the degrees of range of motion available at that joint.
Strength is normally tested as maximum tension produced under voluntary control (Flinn et al., 2008). The strength assessment used most often is manual muscle testing, in which the therapist (alone or using some instrument) tests the ability of the person to produce resistance and/or movement under standardized circum-stances. When no instrument is used, the proce-dure for manual muscle testing is asking the client to move against gravity followed by the break test if the client is capable of moving the body part against gravity. In the break test,
the muscle tested is positioned to give it the most mechanical advantage and the client is asked to hold the position as the therapist increases resistance against it. The extent of effort required for the therapist to break the contraction (i.e., the amount of resistance under which the client can no longer hold the position) is used to grade the client’s strength.
Strength is graded on an ordinal scale (e.g., normal, good, fair, poor, etc.) or on a numeri-cal snumeri-cale (0–5).
Another procedure for measuring strength is to use an instrument; this procedure is most commonly used to assess hand strength. A num-ber of instruments exist for this purpose (e.g., a dynamometer that measures hand strength).
When using these instruments the therapist asks a client to exert maximal force for a brief period and the instrument measures the extent of force the client produces.
When muscle strength is assessed via manual muscle testing, the results are generally inter-preted in terms of what is normal for an individ-ual of the client’s age and sex. In addition to examining strength of individual muscles and muscle groups, the evaluator may assess the
pattern of muscle strength and weakness. Another approach to examining strength is to compare a client’s ability to do a particular movement against the criteria of how much work is required for a particular kind of task or role.
This practice is common in work-oriented eval-uations of strength. For instance, a therapist might test a client whose job requires lifting an object that weighs 50 pounds to the height of a normal table by asking the client to perform exactly that action.
Endurance can be measured either dynami-cally or statidynami-cally. Static assessment examines how long a client can maintain a contraction.
Dynamic assessments of endurance determine the duration or number of repetitions a client can perform before fatigue occurs or by deter-mining the percentage of maximal heart rate that an activity produces.
When measuring endurance, three factors are ordinarily considered: intensity, duration, and frequency. Intensity is a function of both resistance and speed (e.g., how much is being lifted and how fast). Frequency refers to how often the action is repeated and duration to how long it is kept up. As with evaluations of
An occupational therapist measures a client’s lateral pinch strength using a Baltimore Therapeutic Equipment Work Simulator.
strength, an endurance evaluation can also be done against the criteria of what is required for a particular task or job.
In addition to the more traditional and simple assessments of strength and endurance, several kinds of complex and computer-driven systems are available for muscle strength and endurance testing. These can produce very sophisticated analyses of a person’s movement capacities. The methods that a therapist uses will depend on a number of factors including the context and the overall goals of the therapy and resources available.
Intervention
Methods of intervention are clearly delineated in the biomechanical model. When interventions are aimed at maintaining or restoring function, the method must match not only the targeted limita-tions of motion, strength, and endurance but also their underlying causes, because the latter may determine the most appropriate intervention.
For example, if limited range of motion is due to tightness of soft tissue that is part of the joint, stretching may be used to reduce that tightness and increase range of motion. Stretch-ing is sometimes accomplished actively through movements performed by the client. For exam-ple, a person with limited extension in the fin-gers may be given activities that include picking up objects that require the client to open his hands widely, thus stretching the joints. Stretch-ing can also be done through passive, external means, such as manual stretching that is per-formed by a therapist or the use of splints that apply pressure that passively stretches the soft tissues of the joint.
However, as stressed earlier, the method of intervention for maintaining or restoring func-tion depends on the underlying cause of the problem. For instance, if limited range of motion is due to edema (swelling of soft tissue surrounding the joint), compression may be used to reduce the edema and, thus, increase range of motion. A similar logic surrounds pre-ventive efforts. For example, active and passive range of motion and appropriate positioning may be used to prevent tightening of soft tissues that would constrict range of motion.
Strength is developed by increasing the stress on a muscle through: (1) the amount of resistance offered to the movement; (2) the duration of re-sistance required; (3) the rate (speed of move-ment) of an exercise session; and (4) frequency of sessions. Different types of exercise regimens are available. To increase strength, therapists provide clients opportunities to engage in occupations in which one or more of these demands are gradu-ally increased. These increases in demand result in increases in capacity until a desired level of functioning is reached. Current approaches (such as work hardening) emphasize performing the specific tasks required by the person’s occupation (Ogden-Niemeyer & Land Jacobs, 1989).
Endurance is generally addressed by having clients perform activities that require repeated or sustained movement. If the problem is muscular endurance, then activities will stress repeated use of the involved muscles. If the problem is cardio-vascular, activities will be designed to place mild stress on the cardiopulmonary system and, thus, increase its capacity.
Occupational therapy intervention that seeks to maintain or restore capacities may also make use of physical agent modalities (e.g., electrical stimulation, paraffin baths, heat or cold packs, and ultrasound). Their use arose pri-marily in the 1970s and 1980s (Radomski &
Trombly Latham, 2008). These are considered adjunctive procedures that are supportive to the main emphasis of using occupations to maintain or restore motion (AOTA, 2003). Occupational therapists also use techniques such as passive manipulation (e.g., massage or joint mobiliza-tion) in the same way.
Role of Occupation in Maintenance, Prevention, and Restoration
The traditional view in occupational therapy has been that occupations provide natural and moti-vating circumstances for maintaining muscu-loskeletal functioning. This belief is based on the argument that involvement in meaningful occu-pations employs attention, thereby encouraging greater effort, diminishing fatigue, and diverting attention from pain or fear of movement. Addi-tionally, therapists have argued that occupations provide a form of conditioning that more nearly
replicates the normal demands for movement in everyday life. Reflecting this viewpoint, Trombly Latham and Radomski (2002) suggest the following approach to selecting activities used as a therapeutic media:
The best activity for remediation is one that intrinsically demands the exact response that has been determined to need improve-ment.... Contrived methods of doing an ordi-nary activity to make it therapeutic may dimin-ish the value of the activity in the eyes of the patient. (p. 269)
As this quote implies, the therapist requires knowledge of the kind of functional movements that an activity will require from the participant.
As noted earlier, it was assumed in the past that a therapist could determine what discrete move-ments would be required by doing a biome-chanical activity analysis. Now it is recognized that while it may be possible to determine the overall type of movement required to complete a specific activity, it is not possible to predict the exact pattern of muscle action and joint motion with which a person will accomplish a given task. As Trombly (1995) notes:
The next time the person does the same thing, his or her muscles may be more warmed up, or there may be a slight difference in placement of task object in relation to the active limb, so a new coordinative structure evolves. That is, different muscles may be recruited, or the same muscles used before may be more or less active in order to accom-plish the movement goal in the most efficient way. The motor goal is constant or invariant and requires a constant or invariant response, but this response can be fulfilled by a varying set of muscular contractions. (p. 965)
Thus, contemporary biomechanical activity analysis is less concerned with specific motions and, instead, focuses on functional movements.
That is, therapists pay more attention to the functional purpose of a task, because purpose does appear to exert an organizing influence on movement (Trombly, 1995). This also means that when therapists analyze activities, they need to think about requisite movement in func-tional terms such as holding, grasping, lifting, climbing, pressing, and carrying. These are the
kinds of functional movements that tend to remain stable within occupations while the underlying combinations of muscle action and joint motion that accomplish the functional movements may vary considerably.
While the process of analyzing an activity is viewed differently than in the past, it is still an important element of this model since therapists need to modify occupational activities in order to achieve therapeutic goals. Activities may be modified so as to reduce or alter task demands and thereby prevent musculoskeletal problems.
Therapists may also adapt activities to better match permanently reduced musculoskeletal ca-pacity. Finally, activities may be progressively modified to intensify task demands that will in-crease musculoskeletal capacity. Therapists have several ways to modify an activity including:
1. Positioning the task
2. Adding weights or other devices that provide assistance or resistance to movements performed in the activity
3. Modifying tools to reduce or increase demands
4. Changing materials or size of objects used 5. Changing the method of accomplishing
the task
In doing activity adaptation, Trombly Latham and Radomski (2002) caution that the therapist should not contrive the activity so much that it becomes meaningless. In all cases of using adapted activities, it is important that the client be involved in occupational perform-ance that has some meaning and relevperform-ance.
Compensatory Intervention
Compensatory interventions are used for clients who will live with a disability either temporarily or permanently. Underlying such intervention is the principle that when persons do not have the biomechanical capacity to perform daily living, leisure, and work tasks in ordinary ways, special equipment and modified procedures can com-pensate. They are used to close the gap between the person’s capacities and the task demands.
The desired goal of the treatment is for clients to be able to use their remaining capacities (and by so using, maintain them) while being able to participate in the occupations they wish to do.
Evaluation includes assessment of actual performance in activities of daily living (e.g., toileting, bathing, feeding, grooming, dressing, mobility, and communication), leisure, work, and community living. When assessment is completed and the person’s inability to per-form necessary tasks is identified, the therapist determines the biomechanical limitations and assets. With this information, the therapist can recommend and train persons in the use of special equipment, modified procedures, or altered environments that make it possible for the person to perform the task. A wide range of adaptive equipment (commercially available or fabricated in therapy) is used to assist per-sons in performing every aspect of their daily occupations.
Compensatory intervention falls into three broad categories:
•Use of orthoses and prostheses
•Use of adaptive equipment
•Task and/or environmental modification Orthoses can align a body part in proper posi-tion, reduce stress to a joint by providing stability, compensate for weak muscles, or pro-vide a low-grade stretch. The earliest orthoses were fabricated by occupational therapists and while therapists still engage in splint fabrica-tion, a wide variety of prefabricated splints are commercially available. Orthoses support, immo-bilize, or position a joint or joints and are used to correct for deformities and/or to increase function. An orthosis may be temporary or per-manent. Orthotic splints either use existing movements to achieve functional motion or rely on sources of power external to the body.
Occupational therapists are also involved in training clients to use prostheses.
Adaptive equipment exists to interface between musculoskeletal capacities and environ-ment and task demands. Some equipenviron-ment is quite simple, involving modification of ordinary tools and implements to make them easier to grasp and be manipulated. Some involves modification of the environment (i.e., adding ramps and grab bars) to make it easier for persons with limited biomechanical capacity to get around. There also exists more sophisticated equipment such as motorized wheelchairs, special communication
devices, environmental controls, and modified workstations.
The occupational therapist identifies, in collaboration with the client, the most appropri-ate device and/or modified procedure to use in occupational tasks. The therapist also provides instruction and practice in how to make use of compensatory devices and procedures. This can include instructing persons in how to organize
Box 7.1 Improving Functioning Through Use of a Prosthesis
In this photo Karen Roberts is working with a client to prepare her to use a myoelectric prosthesis.
Jacqueline had an amputation when she was a teenager and only wore a prosthesis for a very short time. During the past 15 years Jacqueline has devel-oped overuse problems in her back and her right arm that manifest as pain when she completes her daily occupations. She hopes that a prosthesis may enable her to engage in some bimanual activities with im-proved posture and decreased discomfort. To operate this type of prosthesis, Jacqueline’s muscles need sufficient strength to enable the prosthesis to open and close; she also needs to increase her muscle endurance so that she can use a prosthesis through-out an entire day. The myoelectric training program involves using a type of biofeedback machine that measures the strength of a muscle contraction.
Karen can measure endurance over time based on how long Jacqueline is able to continue performing adequate contractions. Jacqueline works on her muscle capacity through a home exercise program and in time they will use a training prosthesis to practice daily occupations.
their tasks and time to make the best use of existing capacity to accomplish their occupa-tional tasks.
The occupational therapy setting is often used for persons to try out adapted equipment and procedures. Also, as therapists increas-ingly provide services in homes, schools, and workplaces, they can work even more specifi-cally in the natural setting in which the task is to be performed. Therapists may assist individ-uals in planning changes in their homes (if this is financially feasible) and in learning to access specialized transportation and commu-nity facilities.
Work Hardening
Work hardening is an individualized biome-chanical approach to treatment aimed at return-ing an individual to work, usually to a specific job. One of the main methods used in work hardening is physical reconditioning, the use of simulated and real work activities along with exercise to improve the person’s ability to perform specific work tasks.
Work hardening programs employ a range of equipment, including exercise and aerobic condi-tioning equipment, work capacity evaluation devices (that simulate the required movements of work tasks), work samples and workstations that simulate real jobs, and individualized simu-lations that reproduce a specific job requirement (Basmajian & Wolf, 1990; Riccio, Nelson, &
Bush, 1990).