ERICKSTAD, Chief Justice.
The North Dakota Workers Compensation Bureau appeals from the judgment of the District Court for Burleigh County reversing the Bureau’s decision which awarded Diane Roggenbuck benefits only on a fifty percent aggravation basis. We affirm the district court and remand to the Bureau for an appropriate determination of benefits.
On October 20, 1988, Roggenbuck was injured when she fell in the Kirkwood Mall parking lot after leaving her place of employment at Orange Julius. At that time, she was diagnosed, by Ralph Aas, D.C., as suffering from cervical subluxation, cervical cranial syndrome, sacroiliac subluxation, and sprain or strain. On October 24, 1988, Roggenbuck applied for workers’ compensation benefits for those injuries arising out of that fall at work. The Bureau accepted liability and paid the associated medical expenses.1
Subsequent to the incident in the Kirk-wood Mall, Roggenbuck continued to receive chiropractic treatment from Dr. Aas. Although the treatments resolved some of Roggenbuck’s symptoms, her symptoms generally worsened over time. Eventually, Aas concluded that Roggenbuck had a disk problem and on August 29, 1989, he referred her to an orthopedic surgeon.
On September 3, 1989, Roggenbuck, and a neighbor of hers, lifted a gas stove into a child’s wagon so it could be taken to the neighbor’s place to be pressure cleaned. While in the process of pulling the wagon, the neighbor slipped and Roggenbuck tried to “catch” or “steady” the stove to keep it from falling. Apparently, this act of “steadying” the stove caused Roggenbuck to experience some increased pain in her back. The next morning, Roggenbuck went to work as usual, but approximately four hours later, the pain became so intense that she went to the emergency room of St. Alexius Medical Center where she was admitted. An MRI scan revealed that Roggenbuck had a large herniated disk. On September 6, 1989, Roggenbuck underwent surgery to correct the disk problem.
In early September, 1989, Roggenbuck informed the Bureau of the surgery and of post-operative disability. On September 19, 1989, Roggenbuck made a claim for benefits in conjunction with the October 20, 1988, incident. The Bureau thereafter contacted Roger Kennedy, M.D., the physician who treated Roggenbuck for the disk herniation, and Ralph Aas, D.C., for medical records and opinions as to the relationship between the 1988 slip and fall incident, the 1989 steadying of the stove, and the subsequent surgery. On April 2, 1990, the Bureau sent a letter to Dr. Kennedy, asking him to apportion percentages of causation between the nonwork-related stove moving incident and the prior work-related slip and fall incident. Dr. Kennedy responded that [601]*601he could not apportion the percentages of the injuries on the basis of the work- and nonwork-related incidents. The Bureau, subsequently, on May 15, 1990, awarded benefits for a nonemployment aggravation of an employment injury on a fifty percent aggravation basis pursuant to section 65-05-15(4), N.D.C.C.2
Roggenbuck thereafter made a request for administrative review. An administrative hearing was held on March 4, 1991. The hearing officer, in his findings of fact, conclusions of law, and order of May 16, 1991, affirmed the Bureau’s prior decision, holding that “[cjlaimant’s non-employment injury of September 3, 1989, acted upon claimant’s prior compensable injury and substantially contributed to the need for medical attention and disabling claimant from employment.” Roggenbuck then appealed to the district court which reversed the decision of the Bureau holding that the Bureau had improperly invoked the aggravation statute. This appeal followed.3
Initially, we note that when an administrative agency decision is appealed to this Court, we review the decision of the agency and not that of the district court. White v. North Dakota Workers Compensation Bureau, 441 N.W.2d 908, 909 (N.D.1989). We limit our review to the record before the agency and do not consider the finding of the district court. Asbridge v. North Dakota State Highway Commissioner, 291 N.W.2d 739, 743 (N.D.1980).
Under sections 28-32-19 and 28-32-21, N.D.C.C., we will affirm an administrative agency decision unless one of the six enumerated reasons listed in section 28-32-19, N.D.C.C., is found to exist. In re Annexation of Part of Donnybrook Public School District No. 24, 365 N.W.2d 514, 519 (N.D.1985).
We have noted that our review of administrative agency decisions under section 28-32-19, N.D.C.C., essentially involves a three-step process: (1) Are the findings of fact supported by a preponderance of the evidence? (2) Are the conclusions of law sustained by the findings of fact? (3) Is the agency decision supported by the conclusions of law? Tobias v. North Dakota Department of Human Services, 448 N.W.2d 175, 178 (N.D.1989); Falcon v. Williams County Social Service Board, 430 N.W.2d 569, 571 (N.D.1988).
In determining whether or not an agency’s factual findings are supported by a preponderance of the evidence, “we do not make independent findings of fact or substitute our judgment for that of the agency, but determine only whether a reasoning mind could reasonably have determined that the factual conclusions were supported by the weight of the evidence.” Tobias, 448 N.W.2d at 178; see also Power Fuels, Inc. v. Elkin, 283 N.W.2d 214 (N.D.1979). “This court exercises restraint and will not act as a ‘super board’ when reviewing administrative findings and decisions.” Midwest Property Recovery v. Job Service, 475 N.W.2d 918, 921 (N.D.1991); Matter of Boschee, 347 N.W.2d 331, 335 (N.D.1984).
In this case, the Bureau awarded benefits to Roggenbuck pursuant to section 65-05-15(3), N.D.C.C., which provides:
“In case of aggravation of a prior com-pensable injury by a nonemployment injury, the aggravation statute may be invoked where the nonemployment injury acts upon the prior compensable injury, [602]*602and substantially contributes to the severity, acceleration, or progression of the final result, or, if it acts as a trigger to produce recurrent symptoms, and the trigger is itself a substantial aggravating or accelerating factor. All benefits may be apportioned when the aggravation statute is invoked under this subsection. The aggravation statute may not be invoked if the result is but a natural progression of the compensable injury. [Emphasis added.]”
Thus, the issue before us is whether or not the Bureau properly invoked this provision.
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ERICKSTAD, Chief Justice.
The North Dakota Workers Compensation Bureau appeals from the judgment of the District Court for Burleigh County reversing the Bureau’s decision which awarded Diane Roggenbuck benefits only on a fifty percent aggravation basis. We affirm the district court and remand to the Bureau for an appropriate determination of benefits.
On October 20, 1988, Roggenbuck was injured when she fell in the Kirkwood Mall parking lot after leaving her place of employment at Orange Julius. At that time, she was diagnosed, by Ralph Aas, D.C., as suffering from cervical subluxation, cervical cranial syndrome, sacroiliac subluxation, and sprain or strain. On October 24, 1988, Roggenbuck applied for workers’ compensation benefits for those injuries arising out of that fall at work. The Bureau accepted liability and paid the associated medical expenses.1
Subsequent to the incident in the Kirk-wood Mall, Roggenbuck continued to receive chiropractic treatment from Dr. Aas. Although the treatments resolved some of Roggenbuck’s symptoms, her symptoms generally worsened over time. Eventually, Aas concluded that Roggenbuck had a disk problem and on August 29, 1989, he referred her to an orthopedic surgeon.
On September 3, 1989, Roggenbuck, and a neighbor of hers, lifted a gas stove into a child’s wagon so it could be taken to the neighbor’s place to be pressure cleaned. While in the process of pulling the wagon, the neighbor slipped and Roggenbuck tried to “catch” or “steady” the stove to keep it from falling. Apparently, this act of “steadying” the stove caused Roggenbuck to experience some increased pain in her back. The next morning, Roggenbuck went to work as usual, but approximately four hours later, the pain became so intense that she went to the emergency room of St. Alexius Medical Center where she was admitted. An MRI scan revealed that Roggenbuck had a large herniated disk. On September 6, 1989, Roggenbuck underwent surgery to correct the disk problem.
In early September, 1989, Roggenbuck informed the Bureau of the surgery and of post-operative disability. On September 19, 1989, Roggenbuck made a claim for benefits in conjunction with the October 20, 1988, incident. The Bureau thereafter contacted Roger Kennedy, M.D., the physician who treated Roggenbuck for the disk herniation, and Ralph Aas, D.C., for medical records and opinions as to the relationship between the 1988 slip and fall incident, the 1989 steadying of the stove, and the subsequent surgery. On April 2, 1990, the Bureau sent a letter to Dr. Kennedy, asking him to apportion percentages of causation between the nonwork-related stove moving incident and the prior work-related slip and fall incident. Dr. Kennedy responded that [601]*601he could not apportion the percentages of the injuries on the basis of the work- and nonwork-related incidents. The Bureau, subsequently, on May 15, 1990, awarded benefits for a nonemployment aggravation of an employment injury on a fifty percent aggravation basis pursuant to section 65-05-15(4), N.D.C.C.2
Roggenbuck thereafter made a request for administrative review. An administrative hearing was held on March 4, 1991. The hearing officer, in his findings of fact, conclusions of law, and order of May 16, 1991, affirmed the Bureau’s prior decision, holding that “[cjlaimant’s non-employment injury of September 3, 1989, acted upon claimant’s prior compensable injury and substantially contributed to the need for medical attention and disabling claimant from employment.” Roggenbuck then appealed to the district court which reversed the decision of the Bureau holding that the Bureau had improperly invoked the aggravation statute. This appeal followed.3
Initially, we note that when an administrative agency decision is appealed to this Court, we review the decision of the agency and not that of the district court. White v. North Dakota Workers Compensation Bureau, 441 N.W.2d 908, 909 (N.D.1989). We limit our review to the record before the agency and do not consider the finding of the district court. Asbridge v. North Dakota State Highway Commissioner, 291 N.W.2d 739, 743 (N.D.1980).
Under sections 28-32-19 and 28-32-21, N.D.C.C., we will affirm an administrative agency decision unless one of the six enumerated reasons listed in section 28-32-19, N.D.C.C., is found to exist. In re Annexation of Part of Donnybrook Public School District No. 24, 365 N.W.2d 514, 519 (N.D.1985).
We have noted that our review of administrative agency decisions under section 28-32-19, N.D.C.C., essentially involves a three-step process: (1) Are the findings of fact supported by a preponderance of the evidence? (2) Are the conclusions of law sustained by the findings of fact? (3) Is the agency decision supported by the conclusions of law? Tobias v. North Dakota Department of Human Services, 448 N.W.2d 175, 178 (N.D.1989); Falcon v. Williams County Social Service Board, 430 N.W.2d 569, 571 (N.D.1988).
In determining whether or not an agency’s factual findings are supported by a preponderance of the evidence, “we do not make independent findings of fact or substitute our judgment for that of the agency, but determine only whether a reasoning mind could reasonably have determined that the factual conclusions were supported by the weight of the evidence.” Tobias, 448 N.W.2d at 178; see also Power Fuels, Inc. v. Elkin, 283 N.W.2d 214 (N.D.1979). “This court exercises restraint and will not act as a ‘super board’ when reviewing administrative findings and decisions.” Midwest Property Recovery v. Job Service, 475 N.W.2d 918, 921 (N.D.1991); Matter of Boschee, 347 N.W.2d 331, 335 (N.D.1984).
In this case, the Bureau awarded benefits to Roggenbuck pursuant to section 65-05-15(3), N.D.C.C., which provides:
“In case of aggravation of a prior com-pensable injury by a nonemployment injury, the aggravation statute may be invoked where the nonemployment injury acts upon the prior compensable injury, [602]*602and substantially contributes to the severity, acceleration, or progression of the final result, or, if it acts as a trigger to produce recurrent symptoms, and the trigger is itself a substantial aggravating or accelerating factor. All benefits may be apportioned when the aggravation statute is invoked under this subsection. The aggravation statute may not be invoked if the result is but a natural progression of the compensable injury. [Emphasis added.]”
Thus, the issue before us is whether or not the Bureau properly invoked this provision. More specifically, the issue is whether or not a reasoning mind could have reasonably concluded that the greater weight of the evidence indicated that the nonem-ployment related injury, of September 3, 1989, substantially contributed to the severity, acceleration or progression of Rog-genbuck’s condition, or if it acted as a trigger to produce recurrent symptoms when the trigger itself was a substantial aggravating or accelerating factor. In essence, the issue is two-fold, i.e.: (1) Whether or not this injury substantially contributed to Roggenbuck’s condition; and (2) Whether or not the result is but a natural progression of the compensable injury. In considering these questions, we recognize that it is for the Bureau to initially answer these questions, and in reviewing its findings, we keep in mind our past decisions.
In light of the ambiguity resulting from the amendments to section 65-05-15, N.D.C.C., we believe it appropriate to consider legislative history and to consider the amendments in light of the previous statutory provisions, to aid us in determining the intent or objective of those amendments. See State v. Mees, 272 N.W.2d 61, 65 (N.D.1978) (“[a]ny amendment or repeal of any part of a statute must also be considered in determining the true subsequent intent and objective of the legislature”); and Blackburn, Nickels & Smith, Inc. v. National Farmers Union Property & Casualty Company, 452 N.W.2d 319, 322 (N.D.1990) (“[w]hen interpreting an ambiguous statute, the court may consider its legislative history and the circumstances under which the statute was enacted.”)
Previously, section 65-05-15, N.D.C.C., read:
“65-05-15. Aggravation of injury or disease — Compensation and benefits not paid for preexisting condition. Compensation shall not be paid for any condition which existed prior to the happening of a compensable injury nor for any disability chargeable to such condition. In case of aggravation of a condition existing prior to a compensable injury and in case of the aggravation of a compensable injury by a nonemployment injury, compensation, medical or hospital expenses, or death benefits, shall be allowed by the bureau and paid from the fund only for such proportion of the disability, death benefits, or expense arising from the aggravation of such prior condition as reasonably may be attributable to such compensable injury. If the degree of aggravation cannot be determined, the percentage award shall be fifty percent of total benefits recoverable if one hundred percent of the injury had been the result of employment. But any compensation paid on the basis of aggravation shall not be less than ten dollars per week unless the actual wages of claimant shall be less than ten dollars, in which event the actual wages shall be paid in compensation. However, in ease of death due to an employment-aggravated condition, burial expenses and special benefits shall be paid in full pursuant to sections 65-05-17 and 65-05-26.”
Our limited review of the legislative history surrounding the amendments to section 65-05-15, N.D.C.C., reveals little which might aid us in construing 65-05-15(3). The amendments to section 65-05-15 were but a small part of a large number of changes which the 1989 legislature made to the workers’ compensation statutes. See S.L.1989, ch. 766. However, we do note that the fiscal note for the proposed legislation indicated that “[a] majority of the changes in this bill will have little or no fiscal impact on the fund.” Furthermore, Dean Haas, apparently speaking for the Workers Compensation Bureau, as reported in the Senate Standing Committee Min[603]*603utes for the bill, stated that the bill was essentially a housekeeping bill.4
The change in the language relevant to nonwork-related aggravations of prior com-pensable injuries appears to be in the nature of further refinement. The new language appears to further refine what is meant by aggravation of a prior compensa-ble injury by referring to “severity, acceleration, or progression” or where something “triggers” recurrent symptoms. The construction to be placed upon the term “substantial” would thus appear to be the primary focus.
In its final decision, the Bureau made the following relevant findings of fact:
“V.
“Claimant sustained an increase in back pain on September 3, 1989, when she lifted a gas stove and had tried to catch it as it slipped in an off-work accident.
******
“VIII.
“In a December 4, 1989, letter to the Bureau, Dr. Kennedy stated that based on claimant’s history, the September of 1989 incident was the immediate precipitating cause for her disc herniation requiring surgery. Further, there was a suggestion of disc herniation that occurred in October of 1988, which caused claimant to have continuous trouble, however, the September of 1989 event really precipitated the operative treatment.
“IX.
“In an April 13, 1990, letter to the Bureau, Dr. Kennedy stated that based on claimant’s history, with the leg symptoms she had, and with the October 20, 1988, injury, it is likely that she sustained a herniated disc at that time although he cannot prove it. The nonem-ployment injury on September 3, 1989, was the immediate precipitating incident of her admission of September 4, 1989. The doctor indicated that he is unable to attribute the percentages of the work or non-work related injury.
******
“XII.
“Dr. Aas testified that claimant’s diagnosis changed over the course of her treatment from December of 1988 to August of 1989. Claimant’s cervical sublux-ation and cervical cranial syndrome resolved itself, and the sacroiliac subluxation and strain remained. Further, during the course of treatment between December of 1988 and August of 1989, Dr. Aas did not impose any lifting restrictions ....
“XIII.
“Dr. Aas testified that after the October 20, 1988, injury claimant did not show any immediate symptoms of a disc problem. Further, Dr. Aas testified that [604]*604the October 20,1988, injury did not cause the disc lesion, however, it did cause a lack of balance or functional disorder of the whole pelvic muscle group, added stress and strain on the whole area involved, and made the area much more susceptible to injury or subsequent injury-
******
“XV.
“Dr. Kennedy testified that he does not believe the single injury of carrying a stove would have caused the disc herniation, as claimant had a large, ruptured, mushy disc for some time. The single incident of carrying a stove would not have caused a disc herniation without some preexisting condition.
“XVI.
“Dr. Kennedy testified that, notwithstanding the September 3, 1989, injury, claimant’s back condition would not have progressed to the condition that he saw her in during his course of medical treatment. Further, the doctor testified that, notwithstanding the September 3, 1989, injury, the claimant could have continued with conservative treatment.”
Initially, we note a few factual discrepancies in the Bureau’s findings. First, as to finding XII, we note that Dr. Aas’ diagnosis also changed to include lumbar subluxation and strain. Further, it is undisputed that on August 29, 1989, Dr. Aas was of the opinion that Roggenbuck had a disk problem, not responding to treatment, for which he referred her to an orthopedic surgeon. As to finding XIII, it is clear from Dr. Aas’ testimony that he did not unequivocally state that the October 20, 1988, fall did not cause a disk lesion.5 Rather, he was of the opinion that the fall lead to a condition where the disk lesion was occurring through a gradual process.6
As to finding XVI, Dr. Kennedy testified as follows:
“Q. In the absence of that — catching that stove and in the absence of any other traumatic type of injury similar to catching a tipping stove, could she have continued with conservative chiropractic treatment for a while?
“A. It’s quite likely. Yes. [Emphasis added.]”
As mentioned above, Dr. Aas indicated that conservative chiropractic treatment was not working.
In support of its decision, the Bureau primarily relies on Dr. Kennedy’s statement that the September 3, 1989, incident was the “immediately precipitating cause for her disk herniation requiring surgery” and the fact that Dr. Kennedy indicated that without the September 3, 1989, inci[605]*605dent, it was likely that Roggenbuck could have continued with conservative treatment for a while.
However, the fact that an incident precipitated the need for treatment, or precipitated an injury’s becoming disabling does not necessarily mean that such an event substantially contributed to the severity, acceleration, or progression of the condition or that it was a substantial factor in it. Likewise, the fact that a person would not have immediately required surgery had the precipitating event not occurred does not necessarily mean the event was in any way a substantial factor. In other words, a precipitating injury or incident may well be a substantially contributing factor, but the terms are not synonymous.
In this case, we find the following relevant testimony from Dr. Kennedy:
“Q. Okay. Dr. Aas indicated in his deposition that he had referred her for evaluation and possible treatment by a neurosurgeon prior to the stove incident, based on her progressive complaints throughout his course of treatment.
“I know Mr. Sorenson has asked you whether you can speculate as to whether she would have required surgery anyway or whether her disk would have ruptured anyway. Does that progressive history which she evidenced indicate that the disk is in fact — or was in fact getting more unstable or becoming more likely to rupture?
“A. I think I understand your question, because in reviewing the records, I felt that she did have a disk injury as early as what we have recorded that first injury because of its lack of response to the usual chiropractic treatments and clear up, and I think I made a statement to that effect.
“There was some radiation of the pain down into the leg, which sounded like a disk protrusion or rupture. I do believe that she had a damaged disk that would intermittently protrude; that it was somewhat unclear because of her history and what I could gather as to whether it had been on the right side sometimes and the left side other times. But I felt certain in my mind that she did have a damaged disk.
“Q. Is it unusual for radiating leg pain to kind of show up on one leg and then another?
“A. Not that unusual. Particularly if it’s a large ruptured disk. And if it’s very mushy or soft — in fact, it can affect both legs at the same time. So if it’s a very soft disk, depending on the way the trunk is bent, it may tend to protrude or rupture one side more than the other, but can affect either leg.
“Q. What did you find on examination when you actually went in for the surgery? What sort of ruptured disk are we talking about?
* * * * * *
“A. I noted that the rim or the anu-lus, which is the rim of the disk, was markedly soft, mushy or softer than normal, indicating that the disk had degenerated beneath it. The rim of the disk was then opened and a large amount of soft, very mushy and fragmented disk material was removed from the disk space. So it was a very soft and mushy disk, literally one that had no consistency to cushion the usual back.
******
“Q. Okay. Someone with a disk like that, what sort of action would trigger the rupture?
“A. Well, when the — when the disk becomes so soft and mushy, it’s usually — takes very little incident to — ‘the straw that breaks the camel’s back’ — to make it, frankly, rupture again, or even a piece of it become extruded or caught under the nerve.
“When it’s so soft, a simple movement of the back, a simple bending forward over the sink to wash your face, a sneeze, any of these things can be the last straw.
“The actual degeneration of the disk where it becomes mushy is a continuous thing and it tends to become worse with time. It’s hard to tell exactly how fast an individual disk is going to deteriorate. [606]*606But as it becomes softer and more deteriorated, it takes less for it to actually rupture out and pinch the nerve, and you can have multiple events along the line. * * * * * *
“A. Well, I think looking at her specific disk that was so degenerated, that the inciting events that caused her hospitalization could have been any of a number of different injuries....
******
“A. Because as a disk deteriorates, the normal motion of the spine produces, if you will, trauma to the disk, so just by a weight of the spine being traumatic to a damaged disk. A trauma means an injury, and there's a lot of evidence that the whole process of disk deterioration is due to minuscule episodes of trauma, if you will, or wearing of the disk. ******
“Q. Okay. I understand. Symptoms may coincide with the herniation, but the herniation may not coincide with the injury?
“A. Yeah. The initial injury may be the one that damaged the disk to make it soft and begin its degeneration. The rupture or protrusion of the disk outward pinching the nerve is heralded by the sciatic pain, which may come and go, so that when you’re talking about an injury, you may actually damage the disk and make it degenerate, but not have a herniation at that moment. It may come later.”
From the above-quoted testimony, it is clear that Dr. Kennedy was of the opinion that Roggenbuck’s disk problem had likely begun with the October 1988 fall and that it progressively worsened until it reached a stage where any number of everyday activities could have precipitated the need for surgery. Dr. Aas was of a similar opinion.7
Under section 65-05-15(3), N.D.C.C., “[t]he aggravation statute may not be invoked if the result is but a natural progression of the compensable injury.” Thus, in some sense, an everyday activity or event can never substantially contribute to the severity, acceleration, or progression of a condition.8 In this case, the precipitating [607]*607event was found to be the moving of the stove.9 However, there is little evidence in the record other than the weight of the stove and the possible effort to steady it on the wagon, which seems minimal, to indicate that the incident with the stove resulted or could have resulted in a condition different from that resulting from an everyday activity or incident. There was no testimony by either doctor which would in any way suggest that the final result in this case was different from that which would have resulted from an everyday activity, such as bending over a sink, had that been the precipitating event.
The trial court, in its memorandum opinion, said: “the event cannot be affirmatively characterized as a ‘substantial’ contributing factor because there is no rational way of quantifying this event in this manner in this case. [Emphasis added.]” We conclude, as the trial court apparently concluded, that a reasoning mind could not have reasonably concluded that the incident with the stove substantially contributed to Roggenbuck’s condition.
For the aforementioned reasons the judgment of the district court is affirmed and this case is remanded to the Bureau for appropriate disposition in accordance with this opinion.
MESCHKE and LEVINE, JJ., and NORMAN J. BACKES, District Judge, concur.
[608]*608NORMAN J. BACKES, District Judge, sitting with the Court, due to the resignation of the Honorable H.F. GIERKE III, as of November 20, 1991.