                    IN THE COURT OF APPEALS OF IOWA

                                   No. 14-0956
                               Filed April 22, 2015


ARCHER DANIELS MIDLAND, INC.,
    Plaintiff-Appellant,

vs.

ROBERT WARREN,
     Defendant-Appellee.
________________________________________________________________


      Appeal from the Iowa District Court for Polk County, Richard G. Blane II,

Judge.



      An employer appeals from the judicial review decision affirming the

workers’ compensation commissioner’s award of permanent total disability

benefits to Robert Warren. AFFIRMED.




      Jordan A. Kaplan and Mark A. Woollums of Betty, Neuman & McMahon,

P.L.C., Davenport, for appellant.

      Bob Rush of Rush & Nicholson, P.L.C., Cedar Rapids, for appellee.



      Heard by Vogel, P.J., and Potterfield and Mullins, JJ.
                                          2


POTTERFIELD, J.

       Archer Daniels Midlands, Inc. (ADM) appeals from the judicial review

decision affirming the workers’ compensation commissioner’s award of

permanent total disability benefits to Robert Warren. On appeal, ADM contends

the district court erred in failing to remand this case to the commissioner for

reevaluation after the district court found one physician’s opinion of causation

was a “nullity,” and argues the causation determination in the absence of that

opinion is not supported by substantial evidence. ADM also maintains Warren’s

pre-injury-date retirement plans—as a matter of law—preclude an award of

permanent total disability.

       Because the commissioner weighed the expert opinion evidence

thoroughly and documented its finding of causation, and the district court

accepted the finding of the commissioner as supported by substantial evidence in

the record, we affirm the causation finding.      Additionally, we do not find the

commissioner’s determination as to industrial disability was irrational, illogical, or

wholly unjustifiable. We therefore affirm the district court’s decision affirming the

Iowa Workers’ Compensation Commissioner’s award of permanent total disability

benefits to Warren.

I. Background Facts and Proceedings.

       Evidence at the arbitration hearing established Warren was born in

February 1949, completed the ninth grade, and later obtained his G.E.D. He

attended Kirkwood Community College and earned diplomas or certificates in

welding, blueprint reading, and pipe fitting. In 1969, Warren suffered a severe,

traumatic right-hip injury after falling twenty-eight feet from a roof that collapsed.
                                         3


The fall resulted in a comminuted fracture of the intertrochanteric area of the right

femur and fractures to the olecranon. Warren underwent a Jewett hip nailing

procedure involving a three and one-half inch nail, a four inch plate, and metallic

screws.

       Warren worked as a welder from 1974 until 1986 when that employer’s

plant closed. From 1975 to 1976, Warren had complained of pain in the right hip

and had an x-ray showing “some motion about the Jewett nail.” At his doctor’s

recommendation, Warren had the Jewett nail removed. On February 27, 1976,

Dr. J. Huey noted Warren’s leg was well healed and released him to return to

work. In 1980, Warren was seen once for left hip pain. Dr. Huey noted leg

lengths were equal and commented “[h]is right hip has an old varus deformity

from a fracture but it looks pretty good, really. It has healed solidly and the head

is viable. The left hip reveals no evidence of degenerative arthritic change.”

Warren worked for a different employer’s manufacturing business from 1987 to

2000. He then drove a semi-truck for about six months.

       On March 19, 2001, Warren began working for ADM. His health was

“excellent” when he started and he was under no restrictions. He worked for six

months in a warehouse moving and stacking bags. From there, he moved to his

permanent job—refinery utility. As a utility worker, Warren was responsible for

moving railcars (preparing them to carry corn syrup) and directing trucks into

proper filling position. Warren’s position included twelve- to sixteen-hour work

days, lifting up to one hundred pounds much of that time. His work “was heavy,

physical labor that required walking on uneven ground, standing, crawling,

stooping, climbing onto and into and out of railcars, climbing steps, bending,
                                         4


twisting, lifting, and pulling, amongst other strenuous physical acts.”   He fell

several times on the uneven rail yard terrain.

      Warren’s right hip began to bother him when the rail car staging area was

expanded, which caused him to walk more.         He was taking ibuprofen and

Tylenol, but these over-the-counter medications provided only limited relief. On

January 28, 2009, Warren went to his family doctor, Dr. Yang Ahn, complaining

of stiffness and pain. A prescription painkiller was prescribed. Pain in his hip

was noted on an April 22, 2009 visit.

      Warren’s symptoms worsened and Dr. Ahn referred him to Dr. Michael

Brooks for evaluation on July 31, 2009. Dr. Brooks’ recorded history included a

progressively worsening condition. The prescribed painkiller initially helped but

eventually provided only moderate relief. Warren’s employment was described

as “a manual position loading and preparing railroad cars for corn syrup.” Dr.

Brooks assessed “[p]olyarthritis with a predominance of osteoarthritis.” He gave

Warren a steroid injection and prescribed a different painkiller. Dr. Brooks also

ordered additional lab studies. On November 5, 2009, Dr. Brooks noted the lab

studies “did not corroborate any systemic inflammation.” Dr. Brooks indicated

the new medications were providing “good overall pain response . . . but [Warren]

continues to have significant arthralgias and myalgias in the arms and in the

legs.” Dr. Brooks concluded, “I’ve discussed the nature of his disease and the

limits of our ability to treat at this point and have suggested he continue

symptomatic control.”

      Warren returned to Dr. Brooks on May 5, 2010, reporting “significant

symptoms of pain, stiffness and chronic fatigue with myalgias” and “problems
                                         5


with right hip pain and stiffness.” Additional pain medication was prescribed. Dr.

Brooks noted, “I’ve discussed the possibility of sending him to one of the

orthopedic surgeons but he’s not anxious to consider that at the present time.

We will monitor his response to these changes and see him back in 4-6 months.”

       The notes from a September 15, 2010 visit with Dr. Brooks include:

       [Warren] continues having symptoms of more diffuse arthralgias
       and myalgias are really more a predominance of pain in the right
       pelvic area down the right thigh. This is worse with walking on
       uneven ground and with weightbearing. He does have an antalgic
       gait when the symptoms become worse and he indicates that the
       symptoms are somewhat waxing and waning in terms of severity.
              ....
              We discussed the possibility of a total hip arthroplasty at
       length today. I reviewed with him the results of the x-ray and
       suggested that his hip pain is unlikely to get better unless
       something is done more definitively. He has multiple questions
       regarding his job situation if he does have the hip replaced and I
       answered those to the best of my ability but recommended that he
       at least have a consultation with one of the orthopedic surgeons to
       discuss the situation as well. He is thinking about that option at this
       point.

       On September 22, 2010, Warren saw Dr. Sandeep Munjal, an orthopedic

surgeon. Dr. Munjal noted, “His work does require significant lifting of loads and

more than twelve hundred steps a day of rough walking.” X-rays demonstrated

“advanced degenerative changes in the right hip with hallmarks of previous

surgery and a valgus alignment of the hip.” Physical examination revealed a

painful right hip, limping, and antalgic gait. Dr. Munjal assessed osteoarthritis of

the right hip and “unexplained poly inflammatory arthropathy.”           Dr. Munjal

“discussed hip replacement in great detail with the patient.”

       Obviously there will be significant concerns regarding his job with
       especially the high amount of loading he has to do. I discussed hip
       replacement in great detail with the patient, including restrictions
       associated with that.       He is thinking about surgery in
                                            6


       February/March prior to his retirement. Activity modifications after
       that.

       On January 12, 2011, Warren returned to see Dr. Brooks and reported he

was scheduled to have right hip joint replacement. “He is aware that he will not

be able to continue his present job after the surgery due to the requirements of

lifting, squatting and climbing associated with his present job.” Dr. Brooks wrote

further,

               I reviewed the situation with him and have elected to have
       him continue the meloxicam and call me with a report in terms of
       what exactly he’s been doing with the tramadol before deciding on
       further pain medications. I like to get him through the surgery and
       off of work for a month or two prior to considering more medications
       and would therefore like to see him back again in about four
       months for reevaluation and assessment of what medications
       would make sense in his new situation after the surgery.

       Warren underwent a right total hip replacement on February 22, 2011. On

May 11, 2011, Dr. Munjal examined Warren and discussed returning to work:

       Regarding return to work, we gave him a return to work slip when
       FMLA is up May 17 with normal restrictions [fifty-pound weight limit;
       the restrictions also included no bending, climbing, crawling,
       kneeling, stooping, twisting or stair steps]. He will let us know if he
       needs anything additional to this . . . . The patient was encouraged
       to resume activities as tolerated. We will see the patient back at
       one year from the time of surgery or sooner if problems.

       On May 13, 2011, Warren was seen for follow-up by Dr. Brooks. Dr.

Brooks noted Warren “is recovering from [hip replacement] quite nicely although

he is still very restricted in terms of his activities and it is clear that he is not going

to be able to go back to work in his previous position because of the restrictions.”

       Warren returned to ADM, but was told his restrictions could not be
                                               7


accommodated. Consequently, Warren’s last date of employment with ADM was

February 18, 2011.1

          On April 5, 2011, Warren filed a petition seeking workers’ compensation

benefits for a cumulative injury. ADM sent Warren for an independent medical

examination (IME) with Dr. William Boulden on June 15, 2011. In his report, Dr.

Boulden opined “Warren’s work activities with Archer Daniels Midland . . . did not

accelerate or cause the osteoarthritis of his hip, for which he had the hip

replacement.” He also wrote,

          I believe Dr. Munjal’s letter dated Febraury 11, 2010, basically
          states what I have stated; that the arthritis was not caused by the
          patient’s work. The patient did physical activities at work and he
          states that the patent’s symptoms may have been aggravated by
          his work, but once again, the arthritis was the cause of the
          operation and the pain is from the arthritis.

          On March 13, 2012, Warren was seen by Dr. Ray Miller for another IME.

Dr. Miller wrote:

          It is my opinion from evaluating Mr. Warren, his medical records,
          and his job requirements, that his work activity during his ten years
          at Archer Daniels Midland were significant physical activities that
          contributed to the progression of osteoarthritis resulting in the need
          for a total hip replacement. Those work requirements accelerated
          the osteoarthritis and the need for a hip replacement.

          On March 19, 2012, Dr. Munjal signed off on a letter from ADM’s attorney

agreeing with Dr. Boulden that Warren’s “symptoms may have been aggravated

by his work, but once again, the arthritis was the cause of the operation and the

pain is from the arthritis.” On May 4, 2012, Dr. Munjal signed his name to a letter

from Warren’s attorney indicating he agreed with Dr. Miller that Warren’s

employment with ADM accelerated his right hip arthritis causing the need for the

1
    Warren was later found to be totally disabled for Social Security disability purposes.
                                           8


total hip replacement. At a June 11, 2012 deposition, Dr. Munjal testified that

Warren’s work activities were not a cause of Warren’s osteoarthritis. After being

told the difference in the definition of probability and possibility, Dr. Munjal said “it

is probable the increased pain was caused by lifting and all the work. Regarding

arthritis, I would say possible because—or it’s possible that, but I don’t know the

answer.”

       Following an arbitration hearing, the deputy commissioner determined,

“The record evidence considered as a whole does not support a finding that

claimant’s right hip osteoarthritis and his need for a right hip replacement were

rational consequences of his work activities for ADM.” In the conclusions of law,

the deputy commissioner wrote:

               As regards to claimant’s claim of a right hip injury, Dr.
       Boulden’s opinion that claimant’s right hip osteoarthritis and need
       for right hip replacement surgery represented a progression of the
       right hip deformities that he had as a result of the valgus deformity
       he developed after his earlier trochanteric fracture and related
       surgery is well reasoned and accepted over the contrary causation
       opinion of Dr. Miller, which is not supported by a rational
       explanation. Claimant has not demonstrated that the right hip
       osteoarthritis that resulted in his having hip replacement surgery
       was a rational consequence of his work duties or that the condition
       was accelerated because of his work duties for ADM.

Consequently, the deputy denied Warren workers’ compensation benefits.

Warren appealed to the commissioner.

       The commissioner reversed the deputy’s arbitration ruling, finding:

              The law as to aggravation of preexisting conditions is well-
       settled. While a claimant is not entitled to compensation for the
       results of a preexisting injury or disease, its mere existence at the
       time of a subsequent injury is not a defense. Rose v. John Deere
       Ottumwa Works, 76 N.W.2d 756 (Iowa 1956). If the claimant had a
       preexisting condition or disability that is materially aggravated,
       accelerated, worsened or lighted up so that it results in disability,
                                        9

      claimant is entitled to recover. Nicks v. Davenport Produce Co.,
      115 N.W.2d 812 (Iowa 1962); Yeager v. Firestone Tire & Rubber
      Co., 112 N.W.2d 299 (Iowa 1961).
             The presiding deputy commissioner’s discussion of
      causation and of pain brought about by work duties does not
      appear to comport with the well-settled law of aggravation of
      preexisting conditions and is discounted as such a standard would
      place a far greater, if not insurmountable burden on an injured
      worker than does the standard set forth in Nicks and Yeager.
      Claimant need not prove any more than the work activities
      materially aggravated, accelerated, worsened, or lighted up the
      progression of his osteoarthritis and resulted in the need for the hip
      replacement surgery.

      The commissioner observed that Warren’s “employment duties were not

significantly discussed within the arbitration decision.” The commissioner wrote:

      Further, [Warren] explained in great detail the duties of moving
      railcars, cleaning and inspecting the railcars, and ultimately filling
      the cars with product and removing the cars from the facility.
      Between [Warren’s] testimony and the job description it is found
      that [Warren’s] work was heavy, physical labor that required
      walking on uneven ground, standing, crawling, stooping, climbing
      onto and into and out of railcars, climbing steps, bending, twisting,
      lifting, and pulling, amongst other strenuous physical acts.
      [Warren] testified that due to the rough terrain in the rail yard that
      he had fallen several times. [Warren’s] work required him to take
      steps to a control room where he input data into a computer.
      [Warren] worked 12-16 hours per day and had worked up to 80
      hours in a week. [Warren] noted about five to six years prior to the
      arbitration hearing that his work duties had changed and brought
      forth more significant right hip complaints. [Warren] testified that:
              My hip—it got to the point where it was really
              bothering . . . . It got to the point where once I got
              down, it would be hard to get back up. My walking
              going up and down the steps got closer. My hip really
              started to bother me a lot. I was fighting the snow
              clear up to my knees and thighs at times, slipping,
              falling. Just—yeah; it really started to tear me up.

(Record citations omitted.)

      The commissioner reviewed the records of Drs. Munjal, Boulden, and

Miller and determined Warren “met his burden to prove that his right hip
                                           10


replacement and disability arose out of and in the course of his employment

duties with [ADM].” Further, the commissioner found Warren had sustained a

twenty-percent impairment to the whole person. The commissioner concluded

Warren “sustained a right hip injury through a cumulative process as an

aggravation of claimant’s preexisting hip condition. That injury manifested itself

on February 18, 2011[,] when claimant left his employment for medical treatment

for the hip condition.”

       The commissioner then addressed the issue of the “extent of claimant’s

loss of earning capacity as a result of his hip replacement.” The commissioner

considered the many factors of industrial disability and concluded Warren had

“sustained an injury which permanently disables him from performing work within

his experience, training, education, and physical capacities,” entitling him an

award of permanent total disability benefits commencing on February 19, 2011.

       ADM filed a petition for judicial review in the district court. The district

court found substantial evidence supported the commissioner’s finding of

causation, despite finding Dr. Munjal’s varying statements in response to the

attorneys’ letters a “nullity.” The district court wrote:

               However, the Court [] still finds that Dr. Miller’s testimony
       sufficiently supports causation between work and the aggravation
       of the osteoarthritis, which aggravated the condition and
       necessitated surgery. The Court disagrees that Dr. Miller makes
       conflicting assertions. Dr. Miller is simply saying in his first opinion
       that no specific injury at work caused the Warren’s pain in his hip
       but rather the normal physical labor contributed to the acceleration
       of his osteoarthritis. [ADM’s] argument regarding the adjectives
       used to describe the contributing factors is also without merit;
       regardless of the adjectives used to describe the contributions, Dr.
       Miller still found the work activities contributed to the progression
       and acceleration of the osteoarthritis which necessitated surgery.
       Therefore, the Commissioner’s finding that the Warren’s right hip
                                           11


       osteoarthritis aggravation was proximately caused by the Warren’s
       work activities is supported by substantial evidence. The existence
       of substantial evidence is especially apparent when the
       Commissioner’s credibility determination of Dr. Boulden is
       considered.
              The Court also finds the Commissioner’s credibility
       determination regarding Dr. Boulden is supported by substantial
       evidence. The Commissioner’s determination that Dr. Boulden’s
       opinion was conclusory seems to be based on the fact that he did
       not fully acknowledge the physical nature of the Warren’s
       employment in his June 15, 2011 IME. This is supported by
       substantial evidence as Dr. Miller’s IME on March 13, 2012
       discussed the Warren’s job duties in depth . . . .
              ....
              Last, the Court finds [ADM’s] argument that the osteoarthritis
       is not work related without merit. As stated the Commissioner’s
       finding of causation between work and the aggravation of the
       osteoarthritis was supported by substantial evidence.
              In conclusion, the Court finds that when the record is
       considered as a whole, the Commissioner’s decision is supported
       by substantial evidence even when the evidence supplied by Dr.
       Munjal is not considered. Dr. Miller’s opinion supports a causal link
       between the Warren’s physical work and the aggravation of the
       osteoarthritis and subsequent surgery. [footnote omitted]
       Furthermore, the Commissioner’s finding of lack of creditability in
       Dr. Boulden was supported by substantial evidence. Last, [ADM’s]
       attempt to attribute the osteoarthritis to other causes fails.

       ADM also contended the commissioner had not adequately considered

Warren’s “planned retirement” in the determination of industrial disability. The

district court rejected this argument, holding the commissioner’s industrial

disability decision was not irrational, illogical, or wholly unjustifiable.2

       The district court denied ADM’s subsequent motion to amend its ruling in

which it argued, “The Commissioner, not the Court, has authority to determine if

Dr. Miller’s opinion alone proves causation by a preponderance of the evidence.”

       ADM appeals.

2
  The district court did reverse the commissioner’s assessment of costs of an audiology
report associated with Warren’s failed claims of hearing loss and tinnitus, and remanded
to the commissioner for a corrected ruling.
                                          12


II. Scope and Standards of Review.

       Iowa Code chapter 17A governs our review of the commissioner’s

decision.   See Iowa Code § 86.26 (2013); Mike Brooks, Inc. v. House, 843

N.W.2d 885, 888 (Iowa 2014). The district court acts in an appellate capacity

when reviewing the commissioner’s decisions to correct errors of law. See Mike

Brooks, 843 N.W.2d at 888. “On appeal, we apply the standards of chapter 17A

to determine whether we reach the same conclusions as the district court. If we

reach the same conclusions, we affirm; otherwise we may reverse.” Id. at 888-89

(citation and quotation marks omitted).

       As the trier of fact, it is the commissioner’s duty to weigh the evidence.

Arndt v. City of Le Claire, 728 N.W.2d 389, 394-95 (Iowa 2007). We will only

disturb the commissioner’s finding fact if it is not supported by substantial

evidence. See Iowa Code § 17A.19(10)(f) (defining substantial evidence as “the

quantity and quality of evidence that would be deemed sufficient by a neutral,

detached, and reasonable person, to establish the fact at issue when the

consequences resulting from the establishment of that fact are understood to be

serious and of great importance”).

              Evidence is not insubstantial merely because different
       conclusions may be drawn from the evidence. To that end,
       evidence may be substantial even though we may have drawn a
       different conclusion as fact finder. Our task, therefore, is not to
       determine whether the evidence supports a different finding; rather,
       our task is to determine whether substantial evidence, viewing the
       record as a whole, supports the findings actually made.

Cedar Rapids Cmty. Sch. Dist. V. Pease, 807 N.W.2d 839, 845 (Iowa 2011)

(citations omitted).
                                         13


III. Discussion.

      A. Medical Causation. As our supreme court has repeatedly emphasized,

“[o]ur decision is controlled in large part by the deference we afford to decisions

of administrative agencies.” Pease, 807 N.W.2d at 844; see Mike Brooks, 843

N.W.2d at 889.

      Medical causation presents a question of fact that is vested in the

discretion of the workers’ compensation commission. Mike Brooks, 843 N.W.2d

at 889; Pease, 807 N.W.2d at 844-45; Dunlavey v. Econ. Fire & Cas. Co., 526

N.W.2d 845, 853 (Iowa 1995).         “[T]he determination of whether to accept or

reject an expert opinion is within the ‘peculiar province’ of the commissioner.”

Pease, 807 N.W.2d at 845 (quoting Deaver v. Armstrong Rubber Co., 170

N.W.2d 455, 464 (Iowa 1969)).

      ADM argues that because the district court’s analysis excluded Dr.

Munjal’s contradictory opinions, this case must be remanded to the

commissioner to reweigh the evidence. ADM relies on McDowell v. Town of

Clarksville, 241 N.W.2d 904 (Iowa 1976), for this proposition. We reject this

argument.

      The district court observed,

      The Agency did not make any clear indication that its finding of a
      preponderance of the evidence required both doctors’ opinions.
      There is no explicit evidence that the Agency would have found
      against causation if only Dr. Miller’s opinion was available. The
      parts of the Agency’s decision that [ADM] quotes show that the
      Agency is considering the opinions of the doctors collectively when
      deciding causation, but it does not show that both Drs. Miller’s and
      Munjal’s opinions are necessary to find causation and that Dr.
      Miller’s opinion alone would be insubstantial.
              More importantly, the Court’s job on judicial review is to view
      the record as a whole to see if substantial evidence supports a
                                        14


      finding of fact. . . . The Court determined that there was substantial
      evidence after it considered the detracting evidence.

      We find no reason to disturb the court’s reasoning.             While ADM

characterizes the district court’s ruling as a determination the commissioner erred

in considering Dr. Munjal’s testimony, the clear language used by the district

court belies that characterization.     The district court recognized that the

commissioner had weighed the opinions of all three experts on the issue of

causation, discussing the specifics of each doctor’s statements and the context

for each opinion. The commissioner reviewed the several doctors’ opinions and

reasoned:

      [Warren’s] right leg deformity resulted in osteoarthritis and further
      opined that the physical nature of claimant’s employment duties
      materially aggravated and accelerated the osteoarthritis and the
      need for the right hip replacement. The opinions of both Dr. Miller
      and Dr. [Munjal] are supported by reference to the work duties of
      claimant and acknowledge that this is a progression of a preexisting
      condition. The opinion of Dr. Boulden stands alone in the record.
      Dr. Boulden’s report fails to acknowledge the physical nature of
      claimant’s employment in the rail yard, finding it immaterial. Dr.
      Boulden merely writes a conclusory statement that claimant’s work
      duties did not accelerate or cause the osteoarthritis of his hip, for
      which claimant had the hip replacement. Following consideration of
      the medical opinions of the three medical experts it is concluded
      that a preponderance of the evidence supports a conclusion that
      claimant’s right hip osteoarthritis was materially and substantially
      aggravated by claimant’s job duties for defendant, requiring a total
      right hip replacement. Claimant has therefore met his burden to
      prove that his right hip replacement and disability arose out of and
      in the course of his employment duties with defendant. It is further
      concluded that claimant has sustained a 20 percent impairment to
      the whole person along with the restrictions ordered by Dr. Miller.

(Emphasis added.)

      In an effort to acknowledge ADM’s arguments on judicial review about the

differing opinions offered by Dr. Munjal, the district court looked at the record
                                          15


without Dr. Munjal’s opinions to determine whether there was substantial

evidence of causation nonetheless. This is not a situation like McDowell, a case

upon which ADM relied in oral arguments, but had not cited in its briefs.

       McDowell involved an appeal where our supreme court was concerned

that the commissioner had not considered all the evidence. See McDowell, 241

N.W.2d at 909. The McDowell court wrote,

              Obviously an administrative agency cannot in its decision set
       out verbatim all the testimony in a case. Obviously also, if the
       agency quotes some testimony, a losing party should not be able,
       ipso facto, to urge successfully that the agency did not weigh all the
       other evidence. But under the particular record before us we are
       concerned that the commissioner may well have overlooked Dr.
       Caulkins’ answers to the written interrogatories. The commissioner
       set out Dr. Caulkins’ weaker original testimony—and then referred
       to this, if we understand the decision correctly, as Dr. Caulkins’
       strongest testimony. Any reference to Dr. Caulkins’ later, stronger
       answers is conspicuously absent. The record indicates to us that
       the commissioner may well have been unaware of those
       interrogatories and answers. This unawareness may have resulted
       from claimant's filing the interrogatories and answers after the first
       hearing had concluded.

241 N.W.2d at 908. The supreme court held, “The proper disposition, however,

was not for the [district] court to find the facts but rather to return the case to the

commissioner for decision on the record already made.” Id. at 909. The court

concluded:

             We thus remand the case to the commissioner to weigh and
       consider Dr. Caulkins’ answers to the written interrogatories, if the
       commissioner did not so weigh and consider them originally, and to
       render a supplemental decision. If the commissioner did weigh and
       consider those answers originally, he should so recite in his
       supplemental decision, and his original finding on causation and
       judgment will stand.

Id.
                                             16

       Unlike McDowell, the commissioner here referenced, quoted, and cited all

of the opinions of all three doctors, then weighed the opinions, giving little weight

to Dr. Boulden, recognizing the contradictory opinions of Dr. Munjal, and crediting

Dr. Miller’s opinions.      Contrary to ADM’s attempt to characterize the district

court’s ruling otherwise, the district court did not reweigh the evidence here.

Rather,     it    determined   there   was    substantial   evidence   supporting   the

commissioner’s conclusion of causation—even without considering Dr. Munjal’s

opinions.        McDowell does not stand for the proposition that remand to the

commissioner is the proper action here.

       Our supreme court has repeatedly held that “if plaintiff was diseased and

his condition was aggravated, accelerated, worsened or ‘lighted up’ by the injury

so it resulted in the disability found to exist plaintiff was entitled to recover.” Rose

v. John Deere Ottumwa Works, 76 N.W.2d 756, 761 (Iowa 1956).                     It has

approved the standard of “material” aggravation or acceleration. Second Injury

Fund of Iowa v. Nelson, 544 N.W.2d 258, 263 (Iowa 1995); Yeager v. Firestone

Tire & Rubber Co., 112 N.W.2d 299, 302 (Iowa 1961). This is the standard the

commissioner applied; we affirm.

       The commissioner found Warren had carried his burden to prove his

employment with ADM materially aggravated his condition causing the need for

hip replacement. This ruling is supported by Dr. Miller’s opinion that Warren’s

“work activity during his ten years at Archer Daniels Midland were significant

physical activities that contributed to the progression of osteoarthritis resulting in
                                              17


the need for a total hip replacement.”3 Dr. Munjal was uncomfortable offering an

opinion about aggravation of a condition but did sign off on a letter from ADM’s

attorney agreeing with Dr. Boulden that Warren’s “symptoms may have been

aggravated by his work.”           The worsening nature of Warren’s condition is

documented in his medical records, which repeatedly note the strenuous nature

of Warren’s work activities. As the commissioner stated, “The opinion of Dr.

Boulden stands alone in the record. Dr. Boulden’s report fails to acknowledge

the physical nature of claimant’s employment in the rail yard, finding it

immaterial.”

          It is the commissioner, as fact finder, who is responsible for determining

the weight to be given expert testimony.            See Sherman v. Pella Corp., 576

N.W.2d 312, 321 (Iowa 1998). “The commissioner is free to accept or reject an

expert’s opinion in whole or in part, particularly when relying on a conflicting

expert opinion.” Pease, 807 N.W.2d at 85. In their appellate capacity, courts

“are not at liberty to accept contradictory opinions of other experts in order to

reject the finding of the commissioner.” Id. Because the commissioner weighed

the expert opinion evidence thoroughly and documented its finding of causation,

and the district court accepted the finding of the commissioner as supported by

substantial evidence in the record, we affirm.

          B. Industrial disability. “Industrial disability is determined by an evaluation

of the employee’s earning capacity.” Pease, 807 N.W.2d at 852; see also IBP,

Inc. v. Al-Gharib, 604 N.W.2d 621, 632 (Iowa 2000). “The commissioner may

consider a number of factors in determining industrial disability, including

3
    Dr. Boulden opined that Warren’s “arthritis was the cause of the operation.”
                                          18


functional disability, age, education, qualifications, experience, and the claimant’s

inability, because of the injury, to engage in employment for which he is fitted.”

Pease, 807 N.W.2d at 852 (citation, internal quotation marks, and alterations

omitted).

       Here, the commissioner determined:

               Claimant is a 63 year old worker who has performed heavy,
       physical labor during his vocational history. Claimant has a limited
       education, having completed only the 9th grade and later obtaining
       his GED. Claimant has obtained training from a community college
       in welding, pipe-fitting, and general construction trades. Claimant is
       not well suited for retraining due to his age and prior educational
       history. Claimant has sustained a significant physical impairment
       from his right hip replacement. He walks with an altered gait and
       may rely upon a cane or other assistance for mobility. Claimant
       cannot return to any of his prior employment positions. The physical
       restrictions set forth by Dr. Miller are severe and would preclude a
       return to any employment within his experience, training, education,
       or physical capacities. Claimant is on social security disability
       benefits. A vocational opinion by Barbara Laughlin, M.A., finds that
       claimant is precluded even from sedentary positions as he can only
       sit for 30 to 60 minutes at a time per Dr. Miller.
               Having considered the various factors of industrial disability
       it is concluded that claimant has sustained an injury which
       permanently disables him from performing work within his
       experience, training, education, and physical capacities. Therefore,
       claimant is entitled to an award of permanent total disability
       benefits.

       ADM argues the commissioner’s determination is erroneous because

Warren “voluntarily retired.” ADM points out Warren’s testimony in which he

agreed that as of October 2010 when he visited his personal physician, he had

planned to retire the following March 2011.

       Because ADM’s challenge to the commissioner’s industrial disability

determination depends on the application of law to facts, we will not disturb the

ruling unless it is “irrational, illogical, or wholly unjustifiable.” See Neal v. Annett
                                         19

Holdings, Inc., 814 N.W.2d 512, 526 (Iowa 2012). The commissioner considered

the relevant factors of functional impairment, age, intelligence, education,

qualifications, experience, and the ability to engage in the employment for which

Warren was suited. See id.; see also Larson Mfg. Co., Inc. v. Thorson, 763

N.W.2d 842, 857 (Iowa 2009) (noting “motivation” as a relevant factor in

industrial disability inquiry).

       In Second Injury Fund of Iowa v. Nelson, 544 N.W.2d 258, 265-67 (Iowa

1995), our supreme court discussed age as a factor in the determination of

industrial disability.    There, the workers’ compensation commissioner had

determined the worker’s “proximity to normal retirement age also affects his

industrial disability. Claimant is near the end of the normal work life. Compared

to a younger worker with the same injury, claimant has lost less future earning

capacity as a result of his injury.” Nelson, 544 N.W.2d at 265. The supreme

court rejected this reasoning:

               Industrial disability measures an injured worker’s lost earning
       capacity.       Factors that should be considered include the
       employee’s functional impairment, age, intelligence, education,
       qualifications, experience, and the ability of the employee to
       engage in employment for which he is suited. Thus, the focus is
       not solely on what the worker can and cannot do; the focus is on
       the ability of the worker to be gainfully employed.
               Even more important for purposes of our discussion here is
       the concept that industrial disability rests on a comparison of what
       the injured worker could earn before the injury as compared to what
       the same person could earn after the injury. Thus, the level of post-
       injury earnings is important evidence of whether the injury impaired
       the worker’s capacity to earn. However, the commissioner here did
       not merely consider whether Nelson had the ability to earn the
       same wages after his shoulder injury as he could earn before his
       shoulder injury. The commissioner compared what Nelson could
       earn over his remaining worklife after his injury with what a
       hypothetical worker with the same characteristics, but younger,
       could earn. This comparison is irrelevant in determining Nelson’s
                                         20

       lost earning capacity. A calculation of the number of years of
       wages lost by Nelson might be helpful in assessing tort damages
       for lost earnings, but that is not the issue in a workers’
       compensation case.
               ....
               When the industrial commissioner concludes, as he did here,
       that an older employee’s industrial disability is less because the
       employee has fewer years left to work, what the commissioner is
       really saying is that the total amount of future lost wages is a factor
       in setting the degree of industrial disability. The incorrectness of
       this analysis is illustrated by applying this concept in another factual
       context. If the total amount of future lost wages affects the amount
       of industrial disability, then highly paid workers would be entitled to
       a greater industrial disability rating than workers in lower-paying
       jobs. This result would occur even though the two workers’
       capacities to be employed at the same level as they were employed
       before the injury are the same. This illustration highlights the fact
       that the comparison made in determining industrial disability is the
       worker’s capacity to earn before and after the injury, not the
       worker’s capacity to earn as compared to other workers.
               We agree with Nelson that the commissioner’s consideration
       of Nelson’s age as a factor reducing his industrial disability because
       Nelson would suffer less total future wage loss than a younger
       worker was erroneous. Our conclusion does not mean that age is
       irrelevant to determining industrial disability. To the extent Nelson’s
       age affects his actual employability, it is appropriately considered.
       As the industrial commissioner recognized in his decision, Nelson’s
       age would limit the retraining options available to him. Additionally,
       one of the vocational rehabilitation experts reported that Nelson
       would “run into the problem of being accepted by [an] employer at
       age sixty” and “at sixty years old you have to have some other skills
       that are pretty marketable if you are going to get on with a new
       employer.” There is simply no evidence in the record that Nelson’s
       age would increase his employability and thereby, reduce the level
       of his industrial disability. Therefore, we hold the commissioner
       committed reversible error in concluding that Nelson had less
       industrial disability than he otherwise would have had merely
       because he was near retirement age.

Id. at 265-67 (citations omitted).

       We note, too, that ADM’s characterization of Warren’s retirement as

“voluntary” is not without question. We first observe that Warren testified he

“wanted to” retire, which is not synonymous with a definite plan to retire.       It
                                            21


certainly does not mean, as ADM contends, that Warren had already retired.

Warren also testified the working conditions “started to tear me up.” The record

also contains evidence that in May 2011 after his hip replacement, Warren was

released to return to work with restrictions. He took those restrictions to ADM

and was informed his restrictions could not be accommodated. Warren testified,

“I pretty much had to take retirement” and he sought Social Security disability

“[a]fter I knew that my—my working days was pretty much shot.” On our review

of the record evidence, we do not find the commissioner’s determination as to

industrial disability was irrational, illogical, or wholly unjustifiable.

       We affirm the district court’s decision affirming the Iowa Workers’

Compensation Commissioner’s award of permanent total disability benefits to

Warren.

       AFFIRMED.
