Donnell Watson appeals the district court’s dismissal of his 42 U.S.C. § 405(g) lawsuit, seeking review of the Administrative Law Judge’s denial of disability benefits and supplemental security income.
FACTUAL AND PROCEDURAL BACKGROUND
On April 17, 1997, Donnell Watson filed an application for Title II disability benefits and Title XVI supplemental security income, alleging that due to a back injury he was unable to work after June 5, 1996. A hearing on the application before the Administrative Law Judge (“ALJ”) resulted in a denial of benefits. Watson requested an appeal with the Appeals Council, which was denied, and ultimately filed a complaint seeking judicial review.
At the time of the hearing before the ALJ, Watson was 51 and had a high school education. Most of his work experience was as a laborer and highway construction worker. Watson injured his back in a work-related accident, while carrying some pieces of iron. He alleged that the accident left him in pain, and unable to return to his work as a laborer.
The medical evidence regarding Watson’s injuries is somewhat inconsistent. Early examinations did not find any significant problems except for some lower back distress that was resolving. Lumbar x-rays taken in May 1997 showed that he had mild degenerative disc disease of the lumbar spine and probable early degenerative changes of the hip joints. An MRI taken in October 1997 showed a broad-based disc protrusion at the L4-5 level, with bilateral recess compromise and nerve root contact.
One orthopaedist, Dr. Allen Johnston (“Dr. Johnston”), reviewed the MRI in March 1998 and found that it showed “clinically significant disc herniation.” Dr. Johnston opined that the disc herniation would probably cause pain, and that Watson should avoid repetitive bending or twisting at the waist, should not work at unprotected heights, should not lift or carry more than 15-20 pounds, and should not stand or sit for greater than 25 to 30 minutes without being allowed to change positions for 5 minutes.
Another orthopaedist, Dr. Lawrence Messina (“Dr. Messina”), examined Watson in February 1998. Dr. Messina found that Watson had degenerative disc disease and that he had restrictions in bending, sitting for long periods of time, and standing still for long periods of time. However, Dr. Messina sent Watson to physical therapy, opining that Watson could be appropriately rehabilitated and returned to gainful employment with minimal restrictions.
During physical therapy, Watson reported alleviation of pain in his left leg, and only slight residual lower back pain. Wat*215son was able to increase the resistance in his back extension exercises from eighty to one hundred and fifty pounds.
Dr. Messina has testified that his examination of Watson did not reveal any objective abnormalities in his lower back, and that the majority of Watson’s problems were caused by the degenerative process in his back. He disagreed with Dr. Johnston’s conclusion that the MRI showed a significantly herniated disc, but agreed with Dr. Johnston’s assessment that Watson would have to avoid bending and standing for long periods of time. He also testified that Watson’s progression in physical therapy indicated that he could lift more than fifteen pounds, though he would not recommend lifting one hundred and fifty pounds.
Watson’s own testimony regarding his injuries indicated at different points that he could stand for fifteen to twenty minutes without pain, and that he could stand for a “good while, maybe hours.” He testified that he could lift thirty to forty pounds continuously and fifty pounds before it started hurting too much, and that he could lift two or three gallons of milk at a time (the ALJ noted that a gallon weighed 17 pounds). He also stated that he suffered from excruciating pain in his lower back and left leg, and that the pain had gotten worse since his injury, but that he experienced some improvement with physical therapy. He took painkillers and medication to help him sleep.
The ALJ concluded that Watson had degenerative disc disease, an impairment which was severe but did not meet the criteria of any of the impairments listed in Appendix 1, Subpart P, Regulations No. 4. Finding that Watson had an exertional capacity for medium work, the ALJ concluded that he was not disabled.
Before the district court, Watson argued that the ALJ erred in concluding that he could perform medium work, that the ALJ erred in applying the Medical-Vocational Guidelines without determining the extent of Watson’s non-exertional impairment for back pain, and that the ALJ improperly failed to consider whether Watson could obtain and maintain employment under Singletary v. Bowen, 798 F.2d 818 (5th Cir.1986). On cross-motions for summary judgment, the district court denied Watson’s motion and granted summary judgment in favor of the Commissioner of Social Security.
Disoussion
We review a Commissioner’s decisions with respect to a denial of SSI benefits to ascertain (1) whether the final decision is supported by substantial evidence and (2) whether proper legal standards were used to evaluate the evidence. Brown v. Apfel, 192 F.3d 492, 496 (5th Cir.1999). Substantial evidence is more than a scintilla but less than a preponderance and is such relevant evidence as a reasonable mind might accept as adequate to support a conclusion. Richardson v. Perales, 402 U.S. 389, 401, 91 S.Ct. 1420, 1427, 28 L.Ed.2d 842 (1971). “If the Secretary’s decision is supported by substantial evidence, the findings are conclusive and must be affirmed.” Marcello v. Bowen, 803 F.2d 851, 853 (5th Cir.1986) (citing Richardson, 402 U.S. at 390, 91 S.Ct. 1420). “Conflicts in the evidence are for the [Commissioner] and not the courts to resolve.” Brown, 192 F.3d at 496 (citing Selders v. Sullivan, 914 F.2d 614, 617 (5th Cir.1990)).
I. There is substantial evidence to support the ALJ’s finding that Watson could perform medium work
Watson argues that the ALJ erred in finding that he was capable of performing medium work. Medium work “in*216volves lifting no more than 50 pounds at a time with frequent lifting or carrying of objects weighing up to 25 pounds.” 20 C.F.R. § 416.967. While Dr. Johnston restricted Watson to lifting no more than 15 to 20 pounds, Dr. Messina disagreed with that restriction, indicating that Watson could lift more weight than that. Watson’s other doctors did not place similar restrictions on lifting. Watson’s own testimony indicated that he could lift up to 50 pounds, and that he could carry two to three gallons of milk at a time (weighing collectively 34 to 51 pounds). Thus, there was substantial evidence to support the ALJ’s finding that Watson could perform medium work.
II. The ALJ did not err in using the Medicalr-Vocational Guidelines
Where a claimant seeks to prove an “inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which ... can be expected to last for a continuous period of not less than 12 months”, 42 U.S.C. §§ 423(d)(1)(A), the ALJ is required to follow a five-step process. Boyd v. Apfel, 239 F.3d 698, 704 (5th Cir.2001). The burden of proving the first four factors in the process is on the claimant. Id.1 In the present case, the ALJ found that Watson had met his burden on the first four factors, so the burden shifted to the Commissioner to prove the fifth factor, namely, that Watson could perform other work.
At the fifth step in the process, to determine whether a claimant is capable of performing other work or is disabled, the ALJ may use the Medical-Vocational Guidelines (the “grid rules”). However, use of the grid rules is only appropriate “when it is established that a claimant suffers only from exertional impairments, or that the claimant’s nonexertional impairments do not significantly affect his residual functional capacity.” Crowley v. Apfel, 197 F.3d 194, 199 (5th Cir.1999). In the present case, the ALJ found that Watson did not have any significant non-exertional impairments that would affect his medium residual functional capacity. Consequently, the ALJ applied the grid rules, determined that there were jobs available for Watson to perform, and found that Watson was not disabled.
Watson asserts that the ALJ erred in finding that he did not have significant non-exertional impairments, arguing that his back pain constitutes such an impairment. The ALJ relied for this finding on the opinion of a state medical consultant, who concluded in September 1997 that Watson possessed a medium residual functional capacity. The opinion of the state medical consultant regarding Watson’s residual functional capacity is not relevant to whether Watson’s back pain constitutes a significant non-exertional impairment. However, the ALJ also relied on Dr. Messina’s testimony that Watson could return to work with minimal restrictions, and on the report of the physical therapist that *217Watson experienced only slight residual pain after the therapy. The ALJ also found that Watson’s statements about his pain were not credible, due to inconsistencies in his testimony. The testimony of Dr. Messina and the physical therapist constitute substantial evidence to support the AL J’s finding.
III. The Singletary standard
Watson argues that the ALJ erred in failing to make a determination that Watson could maintain employment. In Singletary v. Bowen, 798 F.2d 818 (5th Cir.1986) this Court held that “[a] finding that a claimant is able to engage in substantial gainful activity requires more than a simple determination that the claimant can find employment and that he can physically perform certain jobs; it also requires a determination that the claimant can hold whatever job he finds for a significant period of time.” Id. at 822. The defendant-appellee argues, and the district court held, that the Singletary standard applies only to cases of mental illness or episodic deterioration, not physical disability. The district court pointed out that Singletary, and a subsequent case applying the standard, Leatherwood v. Houston Post Co., 59 F.3d 533 (5th Cir.1995), involved a claimant who suffered from mental illness. However, while it is true that Singletary and Leatherwood applied the standard to persons suffering from mental illness, this does not necessarily imply that the standard cannot be applied to people who are physically disabled.
Indeed, we have already applied the Singletary standard to a case involving a woman who suffered from keratosis. See Wingo v. Bowen, 852 F.2d 827 (5th Cir.1988). In that decision, this Court held that a determination that a person is capable of engaging in substantial gainful activity depends on a finding not only that the individual has some chance of being hired, but also, that, taking account of the individual’s exertional and non-exertional limitations, the individual has a reasonable chance, “once hired, of keeping the job.” Id. at 831. We noted that “[a] claimant capable of performing sedentary or light work under the guidelines must have the ability to perform the required physical acts day in and day out in the sometimes competitive and stressful conditions in which all people work in the real world.” Id. (citing Allred v. Heckler, 729 F.2d 529, 533 (8th Cir.1984)). The dissent contends that this language in Wingo amounts to dicta, arguing that we decided the case solely on the ground that the Secretary must consider all of an individual’s limitations when making a determination of ability to engage in substantial gainful activities. But to label this language as dicta would render the decision in Wingo senseless. The Secretary’s error in Wingo was not simply the failure to consider all of the claimant’s impairments, but more importantly, the Secretary’s failure to make a determination that the claimant was capable of maintaining employment. It was because the Secretary was required to make that determination that it was necessary to consider the claimant’s non-exer-tional limitations, in addition to her exer-tional limitations.
The defendant-appellee seeks to cabin the holding in Wingo, arguing that Wingo requires a finding of an ability to maintain employment only where the individual suffers from additional non-exertional limitations that might limit the individual’s ability to work.2 This narrow reading of Wingo would create an irrational distinction, requiring a finding that a person can maintain employment where the individual *218suffers from additional non-exertional limitations, and not requiring such a finding where the individual suffers solely from exertional limitations. The individual’s ability to maintain employment should be relevant to a determination of disability regardless of whether the individual suffers from non-exertional limitations. In the present case, if Watson’s degenerative disc disease prevented him from maintaining employment (e.g., because every number of weeks he lost movement in his legs) this would be just as relevant to a finding of disability as if his back pain prevented him from maintaining employment (e.g., because every number of weeks he was in too much pain to work). This interpretation is further supported by the fact that other federal appellate courts have made similar holdings, arguing that “[a] condition that does not allow a person to work on a regular basis precludes substantial gainful activity.” Dix v. Sullivan, 900 F.2d 135, 138 (8th Cir.1990)3; see also Broadbent v. Harris, 698 F.2d 407, 413 (10th Cir.1983).
Wingo is properly interpreted as applying the Singletary standard to determinations, of physical disability. Consequently, we find that the ALJ erred in failing to determine whether Watson was capable not only of obtaining, but also maintaining employment.
Conolusion
There is substantial evidence to support the ALJ’s findings that Watson is capable of performing medium work and that Watson’s back pain does not constitute a significant non-exertional impairment. However, the ALJ erred in failing to determine whether Watson was capable not only of obtaining employment, but also maintaining it. Therefore, we VACATE the district court’s judgment affirming the ALJ’s decision, and REMAND to the district court with instructions to REMAND to the Secretary for further proceedings to determine whether Watson was capable of maintaining employment.
. The factors are:
(1) An individual who is working and engaging in substantial gainful activity will not be found disabled regardless of medical findings.
(2) An individual who does not have a "severe impairment” will not be found to be disabled.
(3) An individual who meets or equals a listed impairment in [20 C.F.R. pt. 404, subpt. P, app. 1] will be considered disabled without the consideration of vocational factors.
(4) If an individual is capable of performing the work he has done in the past, a finding of “not disabled” will be made.
(5) If an individual’s impairment precludes him from performing his past work, other factors including age, education, past work experience, and residual functional capacity must be considered to determine if other work can be performed.
Id.
. While the dissent accuses us of setting up a straw man by addressing this issue, we consider it appropriate to respond to the arguments advanced by the parties.
. The dissent argues that we interpret Dix too broadly, and that Dix stands only for the proposition that the Singletary standard applies in cases where a claimant suffers from a disability that periodically affects his or her ability to work. But this interpretation of Dix has it exactly backwards: the purpose of applying the Singletary standard in the context of physical disabilities is to make the determination whether the claimant has a disability that periodically affects his or her ability to work, such that the claimant cannot engage in substantial gainful activity. It would be pointless to apply the standard after that determination has been made. Moreover, by interpreting Dix in this manner, the dissent implicitly accepts that the regulations do not adequately address all cases of physical disability. It is precisely for that reason that the Singletary standard must apply in physical disability cases.