United States Court of Appeals
                           FOR THE EIGHTH CIRCUIT
                                    ___________

                                    No. 03-1409
                                    ___________

Espanola Masterson,                 *
                                    *
             Appellant,             *
                                    * Appeal from the United States
      v.                            * District Court for the
                                    * Western District of Missouri.
Jo Anne B. Barnhart, Commissioner   *
of Social Security,                 *
                                    *
             Appellee.              *
                               ___________

                              Submitted: November 21, 2003

                                   Filed: April 9, 2004
                                    ___________

Before WOLLMAN, BYE, and SMITH, Circuit Judges.
                           ___________

SMITH, Circuit Judge.

       Espanola Masterson appeals the district court's1 order affirming the
Commissioner's denial of her Social Security disability claim. The district court found
that substantial evidence of record supported the Administrative Law Judge's ("ALJ")
determination that Masterson could return to her past work as a property manager. On



      1
        The Honorable Gary A. Fenner, United States District Judge for the Western
District of Missouri.
appeal, Masterson contends that the ALJ's decision was not supported by substantial
evidence. We affirm.

                                    I. Background
      Masterson's medical reports show a history of arrhythmia, hyperglycemia,
hypercholesterolemia, a small disc herniation at L4-L5 without nerve impingement,
hypertension generally controlled with medication, mild venous insufficiency,
osteoarthritis, and fibromyalgia. Various physicians treated Masterson over the course
of her claimed disability period beginning September 13, 1999. The trial record
contains numerous medical records, and we summarize the significant reports herein.
Masterson saw Mark A. Greenfield, M.D., on November 4, 1999, complaining of
back pain. An MRI revealed degenerative disc disease from L2-L3 through L5-S1,
central disc bulging at L3-L4, and a small central disc herniation at L5-S1 without
nerve impingement. Dr. Greenfield treated Masterson with a series of steroid nerve
blocks and pain medication.

        Masterson saw Lisa McPeak, M.D., on February 14, 2000, for a consultative
examination at the direction of the Missouri office of Disability Determination.
Masterson mainly complained of arthritic problems in her back, neck, shoulders,
hands, hips, and knees. Masterson reported that she lived with three grandchildren
ages ten, eleven, and fourteen. She was able to care for herself independently and
assist in the care of her grandchildren. She could cook, perform light cleaning, and
lift objects weighing ten to twenty pounds. On examination, Masterson was able to
sit, stand, walk, handle items, hear, and speak without significant problems. She was
also able to get on and off the examination table, which required her to step up on a
stool and then lay down from a seated position. Her joint ranges of motion and
palpation did not reveal significant joint swelling or warmth, but she did have
crepitus in her knees and wrists. Masterson's deep-tendon reflexes and general
strength were normal. Dr. McPeak noted that Masterson experienced generalized joint
tenderness, muscle tenderness, and some range-of-motion limitations due to her

                                         -2-
arthritic complaints. Dr. McPeak reported that Masterson appeared to have functional
mobility skills, although they were slow. Dr. McPeak determined that Masterson
experienced probable osteoarthritis, a history of Wolff-Parkinson-White Syndrome
(an arrhythmia), controlled hypothyroidism, and hypertension. Dr. McPeak also noted
that Masterson's heart and thyroid problems appeared fairly well controlled. Later
anti-nuclear AB and rheumatoid factor testing was negative.

        Finally, a medical record dated December 1, 2000, indicated that a physician
diagnosed Masterson with fibromyalgia, and prescribed exercise and medication to
control the condition. This diagnosis was repeated in two additional records: the first
in a letter written by a nurse used to excuse Masterson from jury duty, and the second
in a check-up report wherein Masterson reported the prior diagnosis.

       At the administrative hearing, Masterson testified that she was fifty-four years
old and had completed two years of college. She lived with and was the sole caretaker
of her three grandchildren. Regarding her daily activities, Masterson testified that she
woke her grandchildren in the morning for school, made herself breakfast, showered,
washed dishes, helped her grandchildren with homework, and went to church. On
good days, she completed household chores, including laundry, and cooked simple
meals. She also went to the store but took along one of her grandchildren to do the
lifting.

        Masterson's past relevant work was as a property manager for an apartment
building. This job required her to sit at a computer and type, perform inspections, file,
deal with residents, decorate for holidays, work with vendors, clean, and make small
repairs. Masterson claimed that she became disabled on September 13, 1999, when
she was no longer able to perform this job due to pain and an inability to walk. She
testified that she was disabled due to insomnia and severe pain in her shoulders, back,
neck, ankles, hips, and knees. Masterson stated that a rheumatologist told her that she
had fibromyalgia, and that she heard about it on television and believed that she had

                                          -3-
similar symptoms. Masterson testified that she could stand for fifteen to twenty
minutes before her legs hurt, walk one to two blocks before tiring, sit for fifteen to
forty minutes until she experienced neck, back, and hip pain, lift five to ten pounds,
and hold a pen for fifteen to twenty minutes before experiencing cramps. Masterson
testified that she could not squat due to pain in her hips, back, and knees, and that she
occasionally experienced shortness of breath and chest pain. She claimed that her left
leg had given out about five times since September 1999. Masterson also claimed that
she sometimes experienced difficulty thinking, expressing her thoughts, and
remembering things.

       Lynn Allen Curtis, M.D., testified as a medical expert at the administrative
hearing. Dr. Curtis testified that the medical evidence confirmed the diagnoses of
arrhythmia, a history of hyperglycemia, hypercholesterolemia, a herniated nucleus
pulposus or herniated disc at L4-5, hypertension, mild venous insufficiency,
osteoarthritis, and fibromyalgia. Dr. Curtis stated that she saw one diagnosis of
fibromyalgia in the record. Dr. Curtis testified that Masterson's arrhythmia was
controlled with medication. There was no muscle atrophy or spasm, and no evidence
of any impingement on the spinal cord due to Masterson's herniated disc. Dr. Curtis
believed that Masterson's hypertension was sometimes controlled with medication
and her thyroid levels improved with thyroid-replacement therapy. Dr. Curtis testified
that the doctors gave no restrictions to Masterson for her right-shoulder spurring.
Based on the medical evidence, Dr. Curtis opined that Masterson could stand and
walk six hours per day and sit for six to eight hours per day if she could get up every
twenty minutes. Dr. Curtis further determined that Masterson had no lifting
restrictions, but she should not use her arms above her head on her right side. Dr.
Curtis gave no opinion regarding Masterson's abilities to bend, twist, squat, and climb
because the record contained little medical evidence related to her back.

      Lesa Keen, a vocational expert, also testified. Keen testified that Masterson's
only past relevant work as a property manager was typically considered skilled and

                                          -4-
light exertionally. However, Masterson described it as heavy work. Keen testified that
a property-manager position typically allows for alternating among sitting, standing,
and walking depending on the specific job duty, but not necessarily at will.

        The ALJ posed a hypothetical question to Keen based on an individual of
Masterson's age, education, and past work experience with the residual functional
capacity ("RFC") to perform light work with a sit/stand option. In response, Keen
testified that that person could perform work as a cashier, machine operator, and
bench assembler. Keen also identified sedentary jobs such as receptionist and order
clerk, which did not include a sit/stand option but included typical rest periods of a
fifteen-minute mid-morning break, a thirty-minute lunch, and a fifteen-minute
mid-afternoon break. Keen stated that the jobs of cashier, machine operator, bench
assembler, receptionist, and order clerk typically would not involve working above
shoulder level.

       Following the hearing, the ALJ denied Masterson's claim after finding that her
complaints of disabling pain were not credible when compared to Masterson's daily
activities and the lack of medical evidence detailing objective findings. The ALJ
determined that Masterson could perform light or sedentary work without right-arm
overhead work, including her previous work as a property manager as it is generally
performed in the economy. Thereafter, the Appeals Council denied Masterson's
request for review. Thus, the ALJ's decision stands as the Commissioner's final
decision.

                                      II. Analysis
       Masterson argues that the ALJ erred in determining that she retained the RFC
to return to her past relevant work. She argues that the ALJ failed to fully investigate
and make findings regarding the demands of her past work or her capabilities.




                                          -5-
        We review de novo the district court's decision upholding the denial of Social
Security benefits. Lowe v. Apfel, 

, 971 (8th Cir. 2000). "We will affirm
the ALJ's findings if supported by substantial evidence on the record as a whole."
Pearsall v. Massanari, 

, 1217 (8th Cir. 2001). "Substantial evidence
is less than a preponderance, but enough that a reasonable mind might accept it as
adequate to support a decision." 

reviewing the record as a whole, we find
that it is possible to draw two inconsistent positions from the evidence and one of
those positions represents the Commissioner's findings, we must affirm the
Commissioner's decision. Young v. Apfel, 

, 1068 (8th Cir. 2000). It is
not our job to reweigh the evidence or review the factual record de novo. McClees v.
Shalala, 

, 302 (8th Cir. 1993). Weighing the evidence is a function of the
ALJ, the fact-finder. Benskin v. Bowen, 

, 882 (8th Cir. 1987). Instead,
we must simply determine whether the quantity and quality of evidence is enough so
that a reasonable mind might find it adequate to support the ALJ's conclusion. Naber
v. Shalala, 

, 188 (8th Cir. 1994).

      The Social Security Act defines disability as the "inability to engage in any
substantial gainful activity by reason of any medically determinable physical or
mental impairment which can be expected to result in death or has lasted or can be
expected to last for a continuous period of not less than 12 months . . . ." 42 U.S.C.
§ 416(i)(1)(A); 42 U.S.C. § 423(d)(1)(A). The plaintiff has the burden of proving that
she has a disabling impairment. Pickner v. Sullivan, 

, 403 (8th Cir.
1993). However, "direct medical evidence of the cause and effect relationship
between the impairment and the degree of claimant's subjective complaints need not
be produced." Polaski v. Heckler, 

, 1322 (8th Cir. 1984).

                         A. Residual Functional Capacity
      Masterson argues that the medical evidence does not support the ALJ's
determination that she retains the RFC to perform her past relevant work.
Specifically, Masterson argues that Dr. Curtis, a nonexamining physician, offered the

                                         -6-
only medical opinion that assessed her RFC. Masterson argues that the ALJ erred in
relying only on Dr. Curtis's opinion to determine that she had the RFC to perform past
work.

       The government responds that the ALJ made specific findings regarding the
duties and exertional level of her past work as a property manager and, in fact, noted
that while the job of property manager was typically performed at the light exertional
level, Masterson performed it at the heavy level.2 However, the government notes that
the ALJ determined that–based on the medical evidence of record, Dr. Curtis's
opinion, and the vocational expert's opinion–Masterson could perform the job of
property manager at the "light" level.

        The ALJ decided this case at step four of the five-step sequential evaluation.
It is the claimant's burden to establish her RFC at step four. Baldwin v. Barnhart, 

, 556 (8th Cir. 2003); Pearsall v. 

. RFC is
defined as "the most [a claimant] can still do despite" his or her "physical or mental
limitations." 20 C.F.R. § 404.1545(a). The RFC "is a function-by-function assessment
based upon all of the relevant evidence of an individual's ability to do work-related


      2
         Masterson cites Warner v. Heckler, 

(8th Cir. 1983), for the
proposition that a finding that a claimant could return to past work as it is performed
in the national economy rather than how that claimant actually performed it is a
finding that claimant could not return to past work. However, in 

, we determined that "[w]here the claimant has the residual functional capacity to
do either the specific work previously done or the same type of work as it is generally
performed in the national economy, the claimant is found not to be disabled." As
such, because Masterson's past work as a property manager is typically performed in
the national economy at the "light" exertional level, and because the ALJ determined
that the medical evidence indicates that Masterson's restrictions cause her to be
limited to light or sedentary work, Masterson could return to her past employment as
a property manager.


                                         -7-
activities." S.S.R. 96-8p. When determining whether a claimant can engage in
substantial employment, an ALJ must consider the combination of the claimant's
mental and physical impairments and determine the claimant's RFC. 

; 

. The ALJ must determine the claimant's RFC
based on all relevant evidence, including medical records, observations of treating
physicians and others, and claimant's own descriptions of his or her limitations. 

ALJ "bears the primary responsibility for assessing a claimant's
residual functional capacity based on all relevant evidence," Roberts v. Apfel, 

, 469 (8th Cir. 2000), we have also stated that a "claimant's residual
functional capacity is a medical question," Lauer v. Apfel, 

, 704 (8th Cir.
2001). "[S]ome medical evidence," Dykes v. Apfel, 

, 867 (8th Cir. 2000)
(per curiam), must support the determination of the claimant's RFC, and the ALJ
should obtain medical evidence that addresses the claimant's "ability to function in
the workplace[.]" Nevland v. Apfel, 

, 858 (8th Cir. 2000). In evaluating
a claimant's RFC, the ALJ is not limited to considering medical evidence, but is
required to consider at least some supporting evidence from a professional. See 20
C.F.R. § 404.1545(c); 

(internal citations omitted).

       In assessing Masterson's RFC, the ALJ particularly relied on Dr. Curtis's and
Dr. McPeak's assessments of Masterson's limitations. The ALJ also noted that none
of the records from treating physicians conflicted with these medical opinions. The
ALJ relied on Dr. McPeak's determinations regarding Masterson's physical abilities,
strength assessments, and joint movement and functioning. The ALJ further noted
that Masterson takes only non-steroidal anti-inflammatory drugs for pain, and that
while he believed that Masterson experienced pain, objective tests showed nothing
more than mild to moderate impairments at best, and that no treating physician
restricted her activities in any way. Finally, the ALJ noted that no physician
diagnosed her with–and she was not treated for–a mental impairment.



                                         -8-
      The "relevant evidence" also included Masterson's own description of her pain
and limitations, see Anderson v. Shalala, 

, 779 (8th Cir. 1995), which the
ALJ considered and found not to be fully credible. Masterson takes issue with the
ALJ's discounting of her pain complaints; however, Masterson fails to show how the
ALJ erred in that assessment. When evaluating evidence of pain, the ALJ must
consider:

      (1) the claimant's daily activities;
      (2) the subjective evidence of the duration, frequency, and intensity of
      the claimant's pain;
      (3) any precipitating or aggravating factors;
      (4) the dosage, effectiveness and side effects of any medication; and
      (5) the claimant's functional restrictions.

Baker v. Sec'y of Health & Human Services, 

, 555 (8th Cir. 1992);

. Because pain, shortness of breath, weakness, or
nervousness, for example, are difficult to measure, the ALJ may not disregard a
claimant’s subjective complaints of pain solely because the objective medical
evidence does not fully support them. Polaski, 

. Rather, the absence of
this evidence is just one of several factors used to evaluate the credibility of the
testimony and complaints. The credibility of a claimant's subjective testimony is
primarily for the ALJ to decide, not the courts, but such assessments must be based
upon substantial evidence. 

; Rautio v. Bowen, 

,
179 (8th Cir. 1988); 

. The ALJ must make express credibility
determinations and set forth the inconsistencies in the record which cause him to
reject the plaintiff's complaints. Robinson v. Sullivan, 

, 839 (8th Cir.
1992); Ricketts v. Sec'y of Health & Human Services, 

, 664 (8th Cir.
1990). It is not enough that the record contains inconsistencies; the ALJ must
specifically demonstrate that he considered all of the evidence. 

plaintiff
claims that the ALJ failed to properly consider subjective complaints of pain, the duty
of the court is to ascertain whether the ALJ considered all of the evidence relevant to

                                         -9-
the plaintiff's complaints of pain under the Polaski standards and whether the
evidence so contradicts the plaintiff's subjective complaints that the ALJ could
discount his or her testimony as not credible. 

.

       The ALJ made specific findings under these requirements, noting: 1) that
Masterson has a good work record; 2) her daily activities as noted in the opinion are
inconsistent with the extreme complaints of pain; 3) she does not take any narcotic
medication; 4) objective tests support only mild to moderate findings; 5) no treating
or examining doctors restricted her daily activities. More significantly, the ALJ
determined that while she did not find Masterson to be pain free, she also did not
credit Masterson's complaints that extreme pain keeps her in bed and limits her
activities to the degree Masterson claims. Our review of the record and hearing
testimony indicates that substantial evidence supports the ALJ's determination that
while Masterson experiences some pain and limitations, her pain complaints are
inconsistent with the medical evidence of record and her own testimony concerning
her daily activities. As such, we find that the ALJ properly determined Masterson's
RFC.

                           B. Investigation and Findings
      Masterson next argues that the ALJ failed to fully develop the record and make
explicit findings regarding the physical and mental demands of Masterson's past
relevant work before comparing her current abilities to that work. In addition,
Masterson argues that the ALJ failed to establish through vocational evidence that she
could perform work at the light exertional level.

     As fully discussed above, our review indicates that the ALJ fully described
Masterson's past work and properly compared that work to her current abilities before




                                        -10-
determining that she could perform work at the light3 exertional level. First, the ALJ
summarized Masterson's testimony regarding her past work duties and credited this
testimony by noting that Masterson "has a good work record" and performed her prior
job as a property manager at the "heavy"4 work level. The ALJ noted that Masterson
presented medical records that indicate that she has some restrictions. However,
Masterson failed to produce any records, particularly records involving her one-time
diagnosis of fibromyalgia, that indicate that her restrictions severely limit her ability
to function to such a degree that she cannot perform daily activities or that restrict her
activities to preclude all work.

       In addition, the ALJ relied on the vocational expert's testimony regarding the
level of exertion (heavy) Masterson's past job required in developing the requirements
of that job as performed by Masterson, and then as normally performed in the national
economy (light). See 20 C.F.R. § 404.1566 (ALJ may use a vocational expert to

      3
          20 C.F.R. § 404.1567(b) provides:

      Light work involves lifting no more than 20 pounds at a time with
      frequent lifting or carrying of objects weighing up to 10 pounds. Even
      though the weight lifted may be very little, a job is in this category when
      it requires a good deal of walking or standing, or when it involves sitting
      most of the time with some pushing and pulling of arm or leg controls.
      To be considered capable of performing a full or wide range of light
      work, you must have the ability to do substantially all of these activities.
      If someone can do light work, we determine that he or she can also do
      sedentary work, unless there are additional limiting factors such as loss
      of fine dexterity or inability to sit for long periods of time.
      4
          20 C.F.R. § 404.1567(d) provides:

      Heavy work involves lifting no more than 100 pounds at a time with
      frequent lifting or carrying of objects weighing up to 50 pounds. If
      someone can do heavy work, we determine that he or she can also do
      medium, light, and sedentary work.

                                          -11-
assess the existence of work in the national economy). Masterson claims that the ALJ
failed to determine the specific mental and physical requirements of her past
job–however, the ALJ's reference to her past work being "heavy" work necessarily
defined the parameters of the exertional level at which Masterson was working. See
20 C.F.R. § 404.1566 (ALJ may take judicial notice of job information in the
Dictionary of Occupational Titles and other noted, reliable job information reports
when assessing the existence of work in the national economy). As such, we find that
the ALJ adequately developed the record regarding Masterson's physical and pain
limitations and properly compared them to the requirements of her past relevant work
as it is performed in the national economy. In doing so, we further find that the ALJ's
decision is supported by substantial evidence, and we affirm.5
                         ______________________________




      5
        The ALJ also moved to step five in the sequential evaluation and determined
that there were other jobs in the national economy that Masterson could perform. At
that point, the burden shifts to the Commissioner to show other work that the plaintiff
could perform in the national economy. 

. However, because
we agree that Masterson could perform her previous job as a property manager at the
light exertional level, our analysis ends at step four of the sequential evaluation.

                                         -12-