Wednesday, February 13, 2008

Exercise Stress Test, Part 2

Relevance to the Need for a Test-Retest Protocol

In good result/performance cases, a claim for benefits is compromised when a single exercise stress test provides apparent and objective evidence of the ability to work that conflict with the medical record. In such cases, the record is typically replete with subjective evidence of claimant's debilitating fatigue following routine exertion that includes walks, running errands, doing household chores, etc. The failure to objectively document post-exertional malaise is a failure to distinguish fatigue from disability. As a cornerstone symptom of CFS, it is imperative to document post-exertional malaise in order to objectively demonstrate the inability to work on a regular and continuing basis. If post-exertional malaise effectively means that the patient who works on Monday will then suffer uncompromising fatigue for several days thereafter, then it is reasonable to assert that there can be no reasonable expectation of regular participation in the national economy.

Poor result/performance cases provide objective evidence for disability but have been successfully challenged on the basis that the claimant malingered on the test. This raises the important issue of the endpoint used to determine both effort and fatigue. End point respiratory quotients (RQs) are widely accepted as objective markers of effort and fatigue. RQs exceeding 1.09 at the end of an 8-12 minute test indicate that peak aerobic capacity has been met and that anaerobic metabolism explains continued participation in the test. An RQ exceeding one coupled with evidence that either (1) Peak VO_2 or (2) heart rates meeting or exceeding 85% of predicted maximal rates is compelling evidence of maximal effort on a stress test.

The ability to do errands and chores is often used as evidence of the ability to work a job every day. Video-surveillance and third-party testimony is permitted to document a claimant's daily activities, e.g., doing household chores, shopping, running errands, attending church, driving a car, etc. (Coffman v. Metropolitan, 2002). However, at least one appeal ruled that the ability to do limited daily activities is not inconsistent evidence of disability. In Smith v. Barnhart (2003), the ALJ found claimant not markedly impaired because she was able to care for her personal needs, perform some household tasks, and regularly attend church and a Bible study. At appeal, this decision was found not to reflect whether the ALJ considered evidence showing that the claimant had difficulty performing her limited daily tasks. The court cited authority that the ALJ must assess such activities by their independence, appropriateness, effectiveness, and sustainability. Additionally, the ALJ did not analyze why claimant's daily activities were inconsistent with her ability to work. "The fact that a claimant is able to engage in limited daily activities, such as washing dishes, doing laundry, and cooking meals does not necessarily demonstrate that she is not disabled."

Nonetheless, specific reference in the medical record of the caloric or metabolic requirements to perform specific jobs or tasks is important. O'Sullivan v. Prudential (2002) explicitly commented on the need for the medical record to specifically document the physician's knowledge of the metabolic requirements for certain jobs. A poor performance on a stress test may not defeat an argument that sedentary work is within the metabolic capability of a claimant. This argument may be supported by reference to Department of Labor Work Category or specific lists of routine and unskilled jobs within the capabilities of persons with aerobic impairments, e.g., stationary security guard, toll booth operator, ticket taker, car lot attendant (Swenson v. Sullivan, 1989). Evidence of the caloric requirements associated with various tasks/jobs and claimant's metabolic capability to perform would greatly support a rebuttal to the argument. This requires a test-retest protocol that measures oxygen consumption values that are readily translated into caloric equivalents.

The following preliminary study conducted at the Pacific Fatigue Laboratory is directly relevant to the issues raised above. The study examines the test-retest protocol and discussion of the results directly connects the legal and scientific considerations relevant to stress testing.



In this study, the exercise test-retest protocol was examined. The objective of the study was to determine whether objective findings of post-exertional malaise could be documented and to determine whether a serial stress test could objectively distinguish fatigue caused by CFS as opposed to fatigue caused by other illnesses. A brief summary is shown in Table 1.

A standardized bicycle protocol was used in six CFS patients and six normal controls. Expired gases were collected throughout the test so that the following values could be determined: Peak oxygen consumption (VO_2peak ml/kg/min), oxygen consumption at anaerobic threshold (VO_2 @AT ml/kg/min), peak respiratory quotient (RQ), and percentage of predicted heart rate (beats/min). The premise of the study was that test-retest variability in these values should not exceed 8% (2). The rationale for examining these values in a serial protocol is as follows:

Peak VO_2 documents maximal aerobic capacity that can be used to measure fatigue, post-exertional fatigue and determine functional work capacity. Oxygen consumption values can be translated into estimates of kilocalories that in turn can be used to compare the energy requirements of various tasks. This allows for an objective determination of the ability to do work and therefore support or deny the existence of disability. Further, evidence of the attainment of Peak VO_2 is one factor that documents maximal exertion in a test.

VO_2 @AT is the intensity of physical work when anaerobic metabolism takes on a significant and increasing role in providing the energy necessary to continue work. Subjectively, this is the point in work that feels as if exhaustion will occur within a relatively short time in the absence of rest or a reduced workload. Objectively, VO_2 @AT documents one parameter on which to explain level of work that cannot be tolerated for long periods because it represents a point when fatigue begins to lead to exhaustion. This too may be translated into one's ability to produce and expend energy (kilocalories) at the onset of fatigue allowing for comparison with the energy requirements of various tasks.

Peak RQ values objectively document the relative contribution of aerobic and anaerobic metabolism at the end of a stress test. Values exceeding one indicate Peak VO_2 has been met and that anaerobic metabolism preferentially contributes to the energy necessary to continue work. Values over 1.0 are widely accepted as an important factor that shows maximal effort was exerted on a test.

85% of Predicted Maximal Heart Rate is a commonly accepted end-point representing fatigue and true effort in a stress test. There should not be exclusive or even preferential reliance on heart rate. While heart rate objectively reflects workload, it is also influenced by other factors, e.g., emotional status, influence of drugs, state of hydration. Further, it has been argued that blunted heart rates are characteristic of the CFS patient (3). Heart rate is important but should not be exclusively relied upon, especially under circumstances where objective documentation of effort is important.


1. Establishment of an MDI

Can the Test-Retest Protocol Support a Diagnosis by Showing Post-Exertional Malaise?

On Test 1, a side-by-side comparison of Controls and CFS patients shows the relatively "good performance" similar to the discussion above examining legal appeals. In O'Sullivan v. Prudential (2002), claimant had a maximal MET level of 9. Here, Test 1 Peak VO_2 values represent maximal MET levels of 8.11 and 7.48, respectively for Controls and CFS patients. Test 1 values alone are not compelling evidence that the CFS patients are significantly more impaired that Controls. Additionally, Peak VO_2, VO_2 @AT, and RQ values show no significant differences between the two groups. This further suggests that metabolic abnormalities are absent.

It is the comparison between tests that shows a disturbing difference between the two groups. Variability from Test 1 to Test 2 in Peak VO_2 and VO_2 @AT values documents impairment in CFS patient but not the controls. Controls show only 2-3% variability while CFS patients declined by an average of 22-27%. Based upon the premise that test-retest variability should not exceed 8%, this study indicates significant impaired metabolic capability as well as an atypical recovery response in the CFS patient but not the Controls. This is directly relevant to a finding of post-exertional malaise.

This type of analysis is precluded when only the results of a single test are available. A serial protocol is required to document debilitating fatigue. The test-retest protocol does what the single test cannot do, namely objectively document post-exertional malaise, a cornerstone symptom upon which a CFS diagnosis can be founded.

Can the Test-Retest Protocol Distinguish CFS from Other Illnesses?

There remains the problem of distinguishing CFS from other illnesses. This raises the question of what results might occur when CFS patients are compared to patients with other illnesses. Wasserman argues that test-retest variability should not exceed 8% in Peak VO_2 and VO_2 @AT values in clinical and normal groups. Weisman reports a summary of five prior studies that examined test-retest variability in patients with different illnesses. The averaged variability in Peak VO_1 and VO_2/AT among patients suffering from chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), and chronic heart failure (CHF) was 7.2% (2).

It is our contention that the dramatic decline in Peak VO_2 and VO_2 @AT values in CFS patients documented in the Pacific study is unique to CFS and, therefore, represents a basis on which to distinguish fatigue caused by CFS as opposed to fatigue caused by other illnesses. Further research is necessary but based on the results of Pacific's study, the potential to better understand and therefore articulate the nature of CFS to both medical and legal arenas is clearly possible.

2. Establishment of the Ability to Work

Can the Test-Retest Protocol More Effectively Document Functional Impairment/Ability to Work?

Metabolic charts state the caloric requirements for certain tasks and VO_2 and VO_2 @AT values can be translated into calorically based documentation of an individual's metabolic ability or state of fatigue in any number of tasks and jobs. Laboratory stress tests that produce such information may provide explicit documentation of specific tasks that may be reasonably and regularly done by the claimant. This goes to the heart of the ability to work every day at a given job and therefore "engage in substantial employment."

This is illustrated using data from the Pacific study from CFS Patients on Test 2 values of Peak VO_2 an VO_2 @AT and a hypothetical CFS patient weighing 150 pounds (68 kg). Oxygen consumption data is translated into Calories on the premise that one liter of oxygen consumed is the equivalent of approximately 5 calories produced and expended.

For example, Peak VO_2 averaged 20.5 ml/kg/min which translates to a maximal ability to aerobically produce and expend 7kcals/min. VO_2 @AT work capacity averaged 11 ml/kg/min which translates into 3.74 kcals/min3.

It is imperative to distinguish the ability to work a regular job from engaging in daily activities that permit frequent and extended rest periods. Providing specific metabolic information from a test-retest format allows discussion of job requirements in terms of Caloric requirements. This is terminology familiar even to the lay person and providesdocumentation required by policy, law, and precedent.

Can the Test-Retest Protocol Distinguish Maximal Exertion from Malingered Effort?

Peak RQ values with minimal variability and with values ranging from 1.09-1.21 give strong objective support that both groups in both tests exerted maximal effort. Unlike the Controls, the CFS Patients experienced a dramatic decline in VO_2 @AT values between tests suggesting impaired metabolism sufficiently serious to result in the onset of fatigue at a significantly lower workload. This data is the type of objective documentation that can support self-reports by CFS Patients of debilitating fatigue following routine exertion.


Proving CFS disability is a mandate for a claimant seeking associated benefits. Examination of legal considerations relevant to the proof of disability and the process of securing benefits is important to CFS research. The alliance of science and law allows for consideration of the development of laboratory findings that have the potential to better understand the nature of CFS and to provide objective and acceptable evidence for CFS disability.

It is our contention that the Pacific study on serial testing reflects this alliance. It is clear that the Pacific study is preliminary and begs further review. But the initial data suggests that the test-retest format offers a superior basis on which to establish disability consistent with SSA policy and other relevant case law. If the preliminary data holds, the contribution to the CFS patient may be immeasurable.


1. Diagnosis requires concurrence of at least four self-reported symptoms that include: (1) short-term memory loss or impaired concentration that causes substantial reduction in previous levels of performance in work, social or personal activities; (2) sore throat; (3) tender lymph nodes in the neck or auxiliary area; (4) muscle pain; (5) joint pain without redness or swelling; (6) non-refreshing sleep; and (7) post-exertional malaise lasting more than 24 hours. Social Security Ruling (SSR) 99-2p (1999).

2. The following lab findings establish the existence of a MDI in CFS patients: An elevated antibody titer to Epstein-Barr virus capsid antigen equal to or greater than 1:5120, or early antigen equal to or greater that 1:640; An abnormal MRI brain scan; Neurally mediated hypotension as shown by tilt table testing or another clinically accepted form of testing; or, Any other lab findings that are consistent with medically accepted clinical practice and are consistent with the other evidence in the case record; for example, an abnormal exercise stress test or abnormal sleep studies. Social Security Ruling (SSR) 99-2p (1999).

3. Unpublished dispositions when used in this paper are not included as legal precedent. Rather, they are included because they offer insight into the legal use and interpretation of stress tests for the CFS patient.


Kansky v. Coca-Cola Bottling Company of New England, (2006 WL 1167781 at D. Mass). Marshall v. Sullivan, 914 F.2d. 248, Unpublished Disposition, 1990 WL 135840 (4th Cir. Va 1990). Mettlen v. Commissioner of the Social Security Administration, 2003 WL 1889011, 86 Soc.Sec.Rep.Serv. 600 (E.D. Tex. 2003). O'Sullivan v. The Prudential Insurance Co. of America, 2002 WL 484847 (S.D.N.Y.). Smith v. Barnhart, 59 Fed.Appx. 901 (7th Cir. In 2003) Unpublished Disposition. Swenson v. Sullivan, 876. F.2d 683 (9th Cir. Wa 1989).


There is no electronic version of the table.

TABLE 1. A summary of the results of the preliminary study with 6 CFS patients and 6 control subjects. The values for peak oxygen consumption (VO_2 Peak) oxygen consumption at the anaerobic threshold (VO_2 @AT), peak respiratory quotient (Peak RQ) and the percent of age-predicted maximal heart rate attained at peak exercise (Predicted HR%) are shown for the first exercise test (Test 1) and the second exercise test (Test 2) administered 24 hours later. The percent variability (Var) between Test 1 and Test 2 is shown to illustrate the magnitude of the difference in between the metabolic responses.


1. SSR 99-2p (1999 WL 271569 (S.S.A.)) April 30, 1999.

2. Weisman, I.M., & Zeballos, J. (Eds.) (2002) Clinical exercise testing. New York: Karger. In Progress in Respiratory Research (Volume 32; C.T. Bolliger, Editor).

3. VanNess, J.M., Snell C.R., Dempsey W.L., Strayer D.R., Stevens S.R. Sub- classifying Chronic Fatigue Syndrome Through Exercise Testing. Med Sci Sports Exerc 2003; 35(6), 908-913.

-------- (c) 2007 The Haworth Press

The "full text" of

Legal and Scientific Considerations of the Exercise Stress Test
Journal: J of Chronic Fatigue Syndrome, Vol 14, No. 2, 2007, pp. 61-75
Authors: Margaret Ciccolella EdD, JD, Staci R. Stevens MA,
ChristopherR. Snell PhD, Mark Van Ness PhD

that was posted to Co-Cure did not include an important table, Table 1 in
this important paper:

            Test 1    Test 2    (Var)

VO2 Peak        28.4        28.9        (2%)

V02@AT        17.5        18.0        (3%)

Peak RQ        1.19        1.21        (2%)

Predicted HR%    94.8        97.6        (3%)


CFS patients

            Test 1    Test 2    (Var)

VO2 Peak        26.2        20.5        (-22%)

V02@AT        15.0        11.0        (-27%)

Peak RQ        1.15        1.09        (5%) (TK: this should be

Predicted HR%    87.0        87.8        (1%)


Also note that this does not match the abstract for:
Diminished Cardiopulmonary Capacity During Post-Exertional Malaise
Journal, J of Chronic Fatigue Syndrome, Vol. 14, No. 2, 2007, pp. 77-85
Authors: J. Mark VanNess PhD, Christopher R. Snell PhD, Staci R. Stevens

Results: "differences between control and CFS, respectively, for test 1: ..
HR% (87.0 ± 25.4%; 94.8 ± 8.8%)."
as the heart rate is inverted.

As the authors calculated the percentage difference between test 1 and test
2 in Ciccolella et al and they are similar within groups across the two
tests, I presume it is correct.  Also they explicitly say it might be a
little lower in people with CFS (1) (appended), I would imagine that the
percentages are the wrong way around in Van Ness et al i.e. it should be HR%
(94.8 ± 8.8%; 87.0 ± 25.4%)


(1) "85% of Predicted Maximal Heart Rate is a commonly accepted endpoint
representing fatigue and true effort in a stress test. There should
not be exclusive or even preferential reliance on heart rate. While heart
rate objectively reflects workload, it is also influenced by other factors,
e.g., emotional status, influence of drugs, state of hydration. Further, it
has been argued that blunted heart rates are characteristic of the CFS
(3). Heart rate is important but should not be exclusively relied
upon, especially under circumstances where objective documentation
of effort is important."

1 comment:

Mike said...

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