Bertha Eichelberger appeals a district court 1 order affirming an administrative decision denying her social security disability benefits. We find no error and affirm.
I. Background
Eichelberger ceased working on March 20, 2000, complaining of shortness of breath, pain in her shoulder and lower back, a rotator cuff tear, high blood pressure, numbness in her hands and feet, and problems with balance. At that time, Ei-chelberger was 53 years old, had a high school diploma, and one year of college education. Her relevant work history included employment as a bench assembler, forklift operator, warehouse worker, packer, and production assembler. Eichelber-ger became primary care giver for her *588 grandchild just prior to leaving her last employment.
Eichelberger sought medical attention and her primary care physician referred her to an orthopedic surgeon, Dr. Scott R. Luallin, for her neck, shoulder, and back complaints. Dr. Luallin attributed her right shoulder pain to a tear of the rotator cuff coupled with a chronic attritional type tear and recommended surgery. To alleviate the pain in her lower back and neck, Dr. Luallin suggested physical therapy. Eichelberger made appointments for physical therapy in early July. On July 6 and 10, however, Eichelberger cancelled her scheduled appointments stating that her grandchild was ill.
On September 1, 2000, Dr. Luallin surgically repaired Eichelberger’s right shoulder. About a week later, Dr. Luallin rated Eichelberger’s rehabilitation potential as good. He proposed a physical therapy regimen for Eichelberger that consisted of two treatment sessions a week for eight weeks-a total of sixteen treatments. Ei-chelberger did not complete the prescribed course of physical therapy. She attended one full session and a portion of another before leaving for non-health related reasons. By the end of September, Eichel-berger had regained some functionality in her shoulder permitting her to again braid her granddaughter’s hair and resume driving. However, Eichelberger told the therapist that she could still not do her household chores.
On September 15, 2000, Eichelberger filed an application for Social Security disability benefits. The Commissioner of Social Security denied her application and she requested a hearing before an Administrative Law Judge (“ALJ”).
In January 2001, Dr. Luallin noted that Eichelberger’s physical therapy progress was slow but steady. His examination revealed reasonably good strength to external rotation and Jobe’s testing. 2 Dr. Lual-lin suggested that Eichelberger continue with physical therapy. On February 5, 2001, Dr. Luallin observed that Eichelber-ger had only attended two of her prescribed physical therapy appointments and recommended that she continue with physical therapy. During her March examination, Dr. Luallin remarked that while Ei-chelberger did not appear to be putting forth her full effort, her range of motion was increasing and she had good shoulder strength and Jobe’s testing. On June 26, Dr. Luallin commented that Eichelberger appeared to have pain associated with weather changes, but stated that he was pleased with her progress and encouraged her to independently do the prescribed exercises.
On September 27, 2001, Eichelberger again complained of shoulder pain with weather changes, and Dr. Luallin noted a mild positive impingement. At that time, Eichelberger’s shoulder strength remained good and her Jobe’s and external rotation testing remained positive. Dr. Luallin indicated that Eichelberger was stable and recommended that she continue to do her prescribed exercises and return when necessary.
On April 4, 2002, an ALJ conducted a hearing on Eichelberger’s claim for social security disability benefits. After the hearing, Eichelberger returned to Dr. Lu-allin and complained of pain in her neck and back. Dr. Luallin observed that Ei-chelberger had complained of neck and back pain for many years and that she had facet arthritis in her lower back that had been treated with physical therapy. Dr. Luallin performed an examination and once again prescribed physical therapy. *589 Thereafter, an MRI of Eiehelberger’s neck revealed multilevel degenerative disc changes with the most prominent abnormality at C4-5 and C5-6. Eichelberger also complained of pain in her knee and an x-ray revealed mild lateral joint-space narrowing. Dr. Luallin prescribed medicine and recommended icing for Eichelberger’s knee. In addition, he recommended continued physical therapy for her back.
On June 27, 2002, the ALJ affirmed the Commissioner of Social Security’s decision to deny Eichelberger disability benefits. Eichelberger filed for review with the Appeals Council of the Social Security Administration. 3 The Council denied review on September 27, 2002, and Eichelberger appealed the ALJ’s decision to federal district court. The district court agreed with the ALJ, and entered summary judgment in favor of the Commissioner of Social Security.
II. Discussion
We uphold the Commissioner’s determinations unless they are not supported by substantial evidence on the record as a whole.
Harvey v. Barnhart,
A. ALJ’s Credibility Assessment
Eichelberger first argues that the ALJ improperly assessed her credibility citing
Simonson v. Schweiker,
In
Polaski v. Heckler,
In this case, the ALJ found that Eichelberger had objectively determinable impairments, but also noted that her incentive to work might be inhibited by her long-term disability check of $1,700 per month.
Gaddis v. Chater,
We will not substitute our opinion for that of the ALJ, who is in a better position to assess credibility.
Brown v. Chater,
B. ALJ’s RFC Assessment
Eichelberger next contends that the ALJ improperly assessed her Residual Functional Capacity (RFC). Pursuant to the Social Security Act, the Social Security Administration follows a sequential evaluation process when determining disability.
See
20 C.F.R. § 416.920;
see also Ramirez v. Barnhart,
A disability claimant has the burden to establish her RFC.
Masterson v. Barnhart,
Eichelberger points us to
Nev-land,
where we reversed an AL J’s decision because he relied on non-treating, non-examining physicians who formed an opinion solely by reviewing the reports of treating physicians. In that case, however, the claimant established that he was unable'to do past relevant work under step four of the sequential disability process.
Id.
In contrast, the ALJ in this case concluded that Eichelberger, at step four, failed to establish an inability to do past relevant work.
Id.
The burden is on the claimant to demonstrate that he or she is unable to do past relevant work.
Id.
Only when the claimant establishes the inability to do past relevant work does the burden of proof shift to the Commissioner. The Commissioner must then prove, first that the claimant retains the RFC to do other kinds of work, and, second that other work exists in substantial numbers in the national economy that the claimant is able to perform.
Id.; Pearsall v. Massanari,
An ALJ, may determine that a claimant is not disabled when he or she can still perform the actual duties of a past relevant job.
Stephens v. Shalala,
As indicated above, the ALJ’s conclusion under step four is supported by substantial evidence. Nonetheless, Eichelberger argues that the ALJ did not suffi
*592
ciently develop the record when considering her RFC. An ALJ has the duty to develop the record independent of the claimant’s burden in the case.
Snead v. Barnhart,
III. Conclusion
We conclude, based on the record as a whole, that the AL J’s decision is supported by substantial evidence. Accordingly, we affirm.
Notes
. The Honorable Fernando J. Gaitan Jr., United States District Judge for the Western District of Missouri.
. These tests are commonly used to measure the progress of a shoulder recovery.
. Missouri is one of the several test states participating in a modification of procedures to include the elimination of reconsideration in the administrative appeals process. See 20 C.F.R. § 404.906.
