Recent discoveries in neurophysiology have shed some light on the above limitations. These findings raise issues about the voluntary nature of movements, psychogenic movement disorders (PMDs), and the relationship between the brain and changes that occur in the brain of persons suffering from chronic pain. The most frequent clinical presentation of a worker who presents with inconsistent performance on a motor task (such as lifting) is that of pain as the “cause” of the limitation in performance. The qualitative impression of the examiner (usually a therapist) is that the effort being given is submaximal. Some basic physiological measurements, such as changes in blood pressure, heart rate, and respiratory rate, could be (and are) used to determine whether the worker being examined has given sufficient effort to change his baseline cardiovascular physical state. However, these changes in vital signs are most often a reflection of the deconditioned state: poor exercise tolerance causing elevated heart rate response to improve cardiac output. Such elevation in HR can be affected by medications being used by the subject for blood pressure or other conditions and could give a false negative result. A worker with better physical conditioning may show minimal elevations in HR and can still improve cardiac output because of better stroke volume. If all we wanted to show was that the worker is deconditioned, we could utilize a standard exercise treadmill test to document this state.

These cardiovascular changes are not under voluntary (“conscious”) control, which is why they are so useful as measures of physical effort. What we would like to find is a measure of motor output (strength or movement) which would identify the upper limit of physical performance of which the worker is capable. We might then compare the quantitative output to normalized values based on height, age, and gender. The grip strength test (e.g., Jamar dynamometer) is an example of such a standardized motor output. There are published values for populations based on heavy versus sedentary physical labor and gender (Rondinelli, Genovese, Katz et al., 2008). The measurement of the three position grip strength test gives a curve which approximates a bell-shaped curve in normal persons. This measurement (three position grip, as well as alternating handgrip test) is also widely considered to be fairly accurate in identifying conscious poor effort (which we will call malingering in the context of workers’ compensation). One often finds the grip dynamometer used in the functional capacity evaluation (FCE). However, there are problems with this method as discussed below.

Unfortunately, these physiological measures are the ones which are best defined in the context of work-related injury assessment, but leave much to be desired in terms of assessing motor capacity (performance). The remainder of the standard FCE relies on these two tests to detect potential malingering. We then must infer that the remainder of the performance on the FCE is probably submaximal or a result of poor effort if these two tests show inconsistent results.

Recent functional magnetic resonance imaging (fMRI) done by neurophysiologists has shown that persons suffering with chronic pain have detectable changes in their brain morphology, consistent with atrophy of gray matter (cortex) (Apkarian, Sosa, Sonty et al., 2004). These changes are clearly beyond the realm of conscious control of the subject and are tied into important areas of cortex involved in motor planning and execution of movement as well as emotional context. While these studies and their interpretation continue, they clearly imply that persistent states of pain may lead to alterations in the brain that can affect other aspects of the afferent (sensory input) and efferent (motor output) of the human being. Afferent input into the central nervous system occurs through the somatosensory neural input from the periphery, mediated by the dorsal horn of the spinal cord. The physiological phenomenon of central sensitization implies that various nociceptive inputs can change the balance between inhibition and excitation of the dorsal horn, with amplification of pain signals and dispersion of such disinhibitory signals to adjacent areas of the spinal cord. Pain is only one of the many types of somatosensory input into the nervous system. Recent physiological reports in patients with fibromyalgia syndrome (a disorder of “central sensitization”) have shown ipsilateral activation of cortex in persons with allodynia tested by stroking the skin. Such patients had abnormal tender point scale examinations consistent with FMS, whereas controls did not show such ipsilateral activation (Fallon, Chiu, Li et al., 2013). The authors concluded that these findings reflected abnormal physiological changes as a result of somatosensory information manifesting as chronic pain. These findings may represent a manifestation of central sensitization and may contribute to clinical symptom severity (Bandak et al., 2012; Fallon et al., 2013). This provides yet another example of how brain physiology may be altered by chronic pain states.

So, persons with chronic pain may show abnormal activation of cortex by physiological measures, as well as brain morphological changes by imaging. How would these findings change our interpretation of a worker’s performance on a test of functional capacity? The results of these recent neurophysiological investigations have not yet been incorporated into practical tests that can be performed in a clinical, as opposed to a research, setting. However, I think these new findings are critically important as we refine and develop new methods to assess the injured worker. These new findings may help to explain some of the deficiencies of the current state of FCE testing.

Central fatigue is a term coined to describe “decline in voluntary activation of muscle” likely due to a combination of “inadequate descending activation of motoneurones and net reduction in motoneuronal activation caused by disfacilitation (involving muscle spindle and tendon organ afferents) and inhibition (involving small diameter group III and IV muscle afferents) acting on spinal and supraspinal sites” (Gandevia, 1999). Central fatigue may manifest as perceived weakness during a test of exertion, such as a FCE. Recent physiological studies reviewed by Gruet et al. highlighted that motor cortex is influenced by other upstream mechanisms (probably arising in the prefrontal cortex and somatosensory cortex) which likely contribute to central fatigue. They postulated that future work using a combination of imaging and corticomuscular coherence methods will be necessary to identify CNS sites associated with supraspinal failure during exercise (Gruet, Temesi, Rupp et al., 2013; Ranieri & Di Lazzaro, 2012).

Some workers may manifest a disorder of movement that has been termed “psychogenic movement disorder” (PMD). These clinical phenotypes may range from complete paralysis of one or more limbs (conversion disorder) to more limited abnormalities such as tremors, unusual adventitious movements (voluntary myoclonus), or dystonia (e.g., writer’s cramp). Neuropsychiatry distinguishes somatoform disorders, including conversion and somatization (not under conscious control), from factitious disorder (done to fulfill a psychological need) and malingering (behavior to achieve a goal) (Kranick, Gorrindo, & Hallett, 2011). None of the currently used physical performance or functional capacity tests can give definite answers in the recognition of these psychogenic disorders (PMD). At the present time, such disorders require neurological examination and neurophysiological assessment (including electroencephalography (EEG), electromyography (EMG), and accelerometer for tremor evaluation). Hallett has reviewed these syndromes and pitfalls in the diagnosis of them (Hallett, 2010; Hallett et al., 2011).

A physician with experience in evaluation of the cardiac, pulmonary, neurological, and musculoskeletal systems should perform a history and physical examination of any injured worker prior to ordering a FCE or other quantitative assessments of physical performance (QPPE). Because of the occurrence of a variety of physical and psychosomatic disorders which could impact the subject’s performance on an FCE or QPPE, an experienced physician needs to assess the entire medical history, medication usage, and work-related events leading up to the consideration of such physical assessment, in order to assess the safety of that worker’s participation in such an evaluation. This always must include the following: review of outside medical records which may document other findings on previous physical examinations that are not seen at the current time, operative reports, and imaging or neurophysiological studies that may have shown abnormalities that are important in the decision to perform and interpret results from an FCE (Mayer, Gatchel, & Polatin, 2000).

History-taking of the injured worker must not only include the clear investigation of the current symptom complex (back pain, leg weakness, etc.) and any previous diagnostic testing that has been performed to date but should also include evaluation of family history for cardiac, neurological, or musculoskeletal problems that might impact the current evaluation. The injured worker’s use of medications should be detailed in the written report, knowing not only what has been prescribed but whether and in what quantities and what dosing schedule the subject actually uses the medication (or not). Various medications can influence heart rate and blood pressure which could impact interpretation of some results of the FCE. Quantitative urine drug toxicology screening is now commercially available (as well as saliva sampling) to document levels of prescribed drugs in the patient’s system, or the presence of illicit substances as well. I consider it good practice to perform such random quantitative screening on any patient who is taking prescribed opioids or other pain medications regularly. Such testing could also uncover subjects who have illicit substances which might make exercise testing hazardous (e.g., cocaine or amphetamines in their system).

The work history should be sufficiently detailed to understand what the current physical requirements of the job are at the time of injury, as well as the worker’s history in previous employment as to his or her work capacity. For example, has there been a recent change of job which increased the physical demands on the worker beyond what the worker’s previous employment required? Such physical work demands assessment will require input from the employer in the form of a written job description or, in some cases, a telephone call to the employer to determine the physical demands of the job if no written description is available. When there are discrepancies between the worker’s statements as to the real job demands and the written job description, a telephone call to the employer is most useful to clarify these issues, and documentation in the written medical record of any discrepancies should be made.

Psychological assessment of the injured worker is conducted as part of the medical evaluation, and those workers who appear to have significant psychosocial dysfunction which may impact performance will require more detailed examination and testing by a psychologist or psychiatrist. The physician who orders the FCE should inquire specifically about the presence or absence of the symptoms of depression or anxiety, which are two of the most commonly encountered psychiatric disorders in the injured worker population. In clinical practice, the author utilizes the Pain Disability Questionnaire (PDQ) to derive the functional and psychosocial dysfunction scores and total PDQ score, as a measure of perceived disability (Anagnostis, Gatchel, & Mayer, 2004). Other commonly used standardized measures include the Roland Morris Disability Questionnaire and the Oswestry Back Disability Index.

The author combines this instrument with the NIH PROMIS short forms for fatigue and sleep disturbance, which commonly are elevated in persons with chronic pain (unpublished data). For workers who have an associated known preexisting physical impairment (e.g., osteoarthritis of the knee), the NIH PROMIS physical function short form 2 is a useful quantitative measure for impairment in activities of daily living which may or may not be related to pain or the work-related injury. All the NIH PROMIS forms are available free of charge and have been standardized to the US population. Other useful forms that are widely available include the Western Ontario McMaster University Arthritis Center (WOMAC) scales for hip and knee osteoarthritis and the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire. The 6th edition of the AMA Guides has recognized the usefulness of the DASH questionnaire and the PDQ by incorporating specific instructions on administering and scoring the tests (Rondinelli et al., 2008).

Social history should include an understanding of the significant persons living in the injured worker’s home; such family members may be able to give information about the impact of the disability in the home environment or provide added insights into what the worker does outside of the work environment. The use of harmful substances such as tobacco and alcohol is documented in the social history. Such interviews of family members also can uncover unsuspected problems such as obstructive sleep apnea (OSA) syndrome, of which the injured worker may be unaware. OSA can be associated with chronic pain, and in my practice, I have uncovered a large number of working age persons with chronic pain who have previously unrecognized OSA. Treatment of the OSA can be successful in improving the subject’s sense of fatigue and daytime alertness and may reduce chronic pain perception. There are available standardized questionnaires for eliciting symptoms of OSA.

Exercise history is an often-neglected aspect of taking a medical history. I recommend asking questions such as the following: “Do you exercise regularly?”, and “Tell me about what you do for exercise regularly?” which are open-ended and allow the examiner to learn more about the subject’s experience or interest in the subject of exercise. This also provides a useful segue to explain the purpose of an FCE and why the examiner wishes to document the worker’s performance in a more detailed way than can be done in the doctor’s examining room.

Physical examination of the injured worker must include vital signs, height and weight and body mass index (BMI) determination. It is critically important to document the blood pressure (BP) and heart rate (HR) at rest. Abnormal values of BP and HR should result in repeating the values at the end of the examination. If these remain abnormal, then the physician must undertake appropriate further steps to evaluate or to consult other specialists in the evaluation of the cause. It would be medically negligent to send an injured worker who is not under treatment for hypertension into an FCE setting where dangerous BP elevation might occur. Such further evaluation might include a 12-lead electrocardiography, laboratory measurement of thyroid function, complete blood count and metabolic function (tests for diabetes and abnormalities of the liver and kidney, e.g., estimated glomerular filtration rate, known as e-GFR), or other appropriate tests based on the remainder of the physical exam and history findings. One of the most important reasons to have a physician examine the claimant before undertaking an FCE is to uncover potential risks that were unknown and prevent harm from the performance of an FCE in those workers with unsuspected health problems.

The BMI, which relates as a ratio the weight in kilograms and the square of the height in meters, can be calculated easily using online resources such as from the National Heart, Lung, and Blood Institute (http://​www.​nhlbi.​nih.​gov/​guidelines/​obesity/​BMI/​bmicalc.​htm) or published tables of values. Some electronic health records also calculate this ratio automatically. Persons are defined as obese when the BMI > 30 and as morbidly obese when BMI > 40. Morbid obesity especially can be associated with significant cardiovascular risks, including heart failure, diabetes mellitus, and hyperlipidemia.

The remainder of the physical examination should be focused on the pertinent organ systems relevant to the injury and usually involves the neurological and musculoskeletal systems. In some cases, more specialized testing may be necessary to determine the presence of abnormal function which might impact the capacity to perform an FCE. Such examples might include assessment of the worker’s pulmonary function by pulmonary function tests, when the history and physical examination point to significant problems in that area, or electrophysiological evaluation (e.g., needle EMG and nerve conduction studies) when neuromuscular dysfunction is suspected.

The neurological examination consists of evaluation of the mental status, speech, cranial nerves, motor functions (strength and tone of muscle), deep tendon reflexes, abnormal reflexes (e.g., Babinski sign), coordination, gait, and station (standing erect, single-legged stance). The musculoskeletal examination should look at active versus passive joint range of motion, including any limitations for the major weight bearing joints (ankle, knee, and hip) and presence of atrophy (measured with a centimeter tape measure) of the arm, thigh, or calf muscles. In some disorders, passive motion may be maintained, but active motion is impaired. Such would be the case with a rotator cuff tear and active shoulder flexion and abduction. Atrophy, especially if unilateral, could imply neuromuscular dysfunction (such as injury to the sciatic nerve or nerve roots to the leg). Leg length should be measured when fracture of a lower extremity long bone has occurred or total joint arthroplasty has been performed.

Provocative tests are somewhat less useful, because there may be a subjective component of pain behavior during their elicitation which is easily feigned by an experienced claimant. However, a test such as the drop arm test which when abnormal indicates lack of musculotendinous integrity of the supraspinatus tendon is a specific indicator of supraspinatus (one of the rotator cuff muscles) injury. The elicitation of Waddell’s signs has been purported to be useful in the evaluation, although in this author’s experience, they are not (Waddell, McCulloch, Kummel et al., 1980). Further discussion later in this chapter will confirm this skepticism. Most importantly, the examining physician should compare his/her abnormal findings on physical examination with the review of previous medical records to determine if the current abnormal findings have been documented previously. When there are new findings or discrepancies with previous findings, these divergences from the previous record should be noted in a report specifically, as they usually are important in understanding the progression or natural history of the injury.

When the findings between the current examiner and those of previous treating physicians and specialists are congruent, and the examination does not reveal abnormal illness behavior, then there is a high likelihood of obtaining a valid result from an FCE. However, when the findings between the current examiner and the previous physicians show noncongruent findings, then the examining physician must decide if the correct diagnosis has been made or if the natural history of the condition has progressed (worsened versus improved) and whether further diagnostic testing is necessary to clarify the diagnosis prior to consideration of FCE. An FCE should not be ordered if the examining physician is not able to state the diagnosis clearly based on objective assessment of the patient using all available data (medical records, history, physical examination, and specialized testing). It is not the responsibility of the therapist who performs the FCE to determine a diagnosis, as that is outside the boundaries of the professional license of the therapist and would risk claim of negligence if harm should result from the FCE due to an unrecognized condition.

The literature up to the end of the twentieth century on quantitative assessment of function (QAF) for work-related injury has been well reviewed (Mayer et al., 2000). In this chapter, we seek to identify more recent published literature that impacts the topic of QAF. To this end, a medical research librarian-assisted English language literature search was made using the search terms (in various combinations) functional capacity, musculoskeletal measurement, work capacity evaluation and reproducibility of results, disability evaluation/reproducibility of results, musculoskeletal diseases/physiopathology, psychology, and pain measurement. In addition, author searches were conducted of three frequently cited authors (Gatchel RJ, Mayer TG, and Haralson III RH). The time period on which we focused was inclusive of 1999–2012. While this chapter has not the same purpose as a systematic review of the literature would provide, we did attempt a comprehensive review (integrative review) to identify issues especially involving the reproducibility of results and sources of error in the interpretation of QAF when used clinically in the assessment of work-related injury and disability. Over 400 articles were found, and the author attempted to utilize the results objectively, but not following the strict format of a systematic review, such as used by the Cochrane Collaboration.