Fourth, if the claimant’s “severe impairment” is not listed in Appendix 1, the ALJ determines whether the claimant maintains the RFC to perform the work that she performed prior to the onset of her impairment (“past work”). Finally, at step five, if the claimant is unable to perform past work, or has no previous work history, the ALJ ascertains whether there is other work that the claimant is capable of performing. See Berry v. Schweiker, 675 F.2d 464, 467 (2d Cir.1982) (per curiam); Morillo, 150 F.Supp.2d at 545. The burden lies with the claimant to prove the requirements of the first four steps, but shifts to the Commissioner at step five. See Berry, 675 F.2d at 467; see also Perez v. Chater, 77 F.3d 41, 46 (2d Cir.1996); Aubeuf v. Schweiker, 649 F.2d 107, 112 (2d Cir.1981) (<HOLDING>) (citation omitted). Where a claimant suffers
holding claimant suffered permanent total disability where functional disability was only twentyfive or thirty percent claimant was fiftynine years of age claimant had little or no education and the injury kept the claimant from performing physical work holding that before terminating benefits the plan should have obtained a vocational experts opinion to determine if claimant is presently capable in light of his physical impairment to perform any occupation  and observing that claimant met his burden when he proved his disability initially holding that when the claimant has established that his impairment prevents him from returning to his previous employment the burden shifts to the commissioner who must produce evidence to show the existence of alternative substantial gainful work which exists in the national economy and which the claimant could perform considering not only his physical and mental capability but also his age education experience and training holding that claimant moving for summary judgment on its claim must conclusively prove all the essential elements of the claim and that claimant has the burden to show that there are no genuine issues of material fact and that claimant is entitled to judgment as a matter of law holding that the burden of proof is on the claimant