Larson Manufacturing Company, Inc., And Atlantic Mutual Companies Vs. Julie Thorson ( 2009 )


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  •                 IN THE SUPREME COURT OF IOWA
    No. 06–1954
    Filed February 13, 2009
    LARSON MANUFACTURING COMPANY, INC.,
    and ATLANTIC MUTUAL COMPANIES,
    Appellants,
    vs.
    JULIE THORSON,
    Appellee.
    Appeal from the Iowa District Court for Polk County, Carla T.
    Schemmel, Judge.
    Employer and its insurance carrier appeal from the district court’s
    decision affirming a decision of the workers’ compensation commissioner.
    AFFIRMED IN PART AND REVERSED IN PART.
    Jeffrey W. Lanz of Huber, Book, Cortese, Happe & Lanz, P.L.C.,
    West Des Moines, for appellants.
    Mark S. Soldat of Soldat & Parrish-Sams, P.L.C., West Des Moines,
    for appellee.
    2
    HECHT, Justice.
    We reversed and remanded this case to the workers’ compensation
    commissioner in Thorson v. Larson Mfg. Co., 
    682 N.W.2d 448
    , 451 (Iowa
    2004).1 After the parties submitted additional evidence on remand, the
    commissioner found Thorson sustained a compensable cumulative
    injury, and ordered the employer and its insurance carrier to pay
    compensation, interest, medical expenses, and the cost of a medical
    examination under Iowa Code section 85.39 (2005). On judicial review,
    the district court affirmed the commissioner’s remand decision.                       We
    affirm in part and reverse in part the commissioner’s decision.
    I.     Factual and Procedural Background.
    Julie Thorson began working for Larson Manufacturing Company,
    Inc.,2 a storm door manufacturer in Lake Mills, Iowa in 1974. Her job
    duties evolved over the years, but consistently involved continuous,
    repetitive movement and occasionally required overhead work.                         For
    approximately the first twenty years of her employment, Thorson’s job
    1The  arbitration decision had excluded the report of Dr. Justin Ban (offered by
    Thorson and asserting she sustained a permanent cumulative injury to her shoulders,
    upper extremities, and cervicothoracic spine) on the ground it was not served within the
    deadline established in a hearing assignment order.             The decision awarded
    compensation for Thorson’s lower extremity injury, but determined Thorson failed to
    prove she sustained a compensable cumulative injury. On judicial review, the district
    court reversed and remanded to the commissioner for application of the manifestation
    standard discussed in our decision in Herrera v. IBP, Inc., 
    633 N.W.2d 284
    , 288 (Iowa
    2001) (establishing that a cumulative injury is manifest when “the claimant, as a
    reasonable person, would be plainly aware (1) that he or she suffers from a condition or
    injury, and (2) that this condition or injury was caused by the claimant’s employment”)
    and directed the commissioner to consider Dr. Ban’s report only to the extent that it
    rebutted certain medical evidence offered by the employer. On appeal, we reversed the
    commissioner’s decision and remanded to the agency for “reconsideration of [Thorson’s]
    claim on the record already made, with the addition of the Ban report and any rebuttal
    evidence that the commissioner allows.” Thorson v. Larson Mfg. Co., 682 N.W.2d at 451.
    2Atlantic    Mutual Companies provided workers’ compensation insurance
    coverage to Larson during times at issue in this case. In the interest of brevity, we will
    refer jointly to Larson and Atlantic as “Larson.”
    3
    duties required her to perform the same repetitive physical tasks for
    eight hours each day.       In 1995 or 1996, Larson implemented a job
    rotation program which allowed employees to change their work station
    each day. The program was later modified to allow Thorson and other
    employees to change stations after each half-day of work.
    Thorson first sought treatment for neck and shoulder pain in 1986
    from Dr. Ronald Masters, a chiropractor, who offered a free clinic for
    patients.       Thorson discontinued chiropractic treatments after four
    months, however, when free services were no longer offered because her
    health insurance did not provide coverage for chiropractic care.
    Thorson next received relevant medical care in August 1992 when
    Larson referred her to Dr. Colby, a family physician, for diagnosis and
    treatment of shoulder and wrist symptoms. Dr. Colby diagnosed lateral
    epicondylitis, and placed Thorson on light duty until October 28, 1992,
    when she was released to full duty with no physician-imposed physical
    restrictions.
    Thorson again consulted Dr. Colby for work-related pain on
    April 26, 1996. Thorson reported she had been experiencing “knots” in
    her lower back, shoulders, and elbows for the past eighteen months.
    Dr. Colby diagnosed back spasms and medial epicondylitis, and again
    placed Thorson on light duty. Although Thorson was informed no real
    light-duty jobs were available, Larson did assign her to a job requiring
    less exertion than her usual work assignments.        Dr. Colby referred
    Thorson to Dr. Toth for physical therapy in July 1996.
    Dr. Toth diagnosed chronic cervical and thoracic spine strain with
    somatic dysfunction, and recommended Thorson continue light-duty
    restrictions with minimal overhead work and less frequent rotating
    movement.       He noted it was difficult for Thorson to work within her
    4
    physical restrictions, apparently referring to the unavailability of light-
    duty jobs at Larson’s plant. Thorson experienced modest improvement of
    her condition at times from the physical therapy.
    On November 25, 1996, after completing the therapy under
    Dr. Toth’s care, Thorson was transferred from Larson’s sub-assembly
    department to the door line. Although this transfer decreased the work-
    related stress on her back and shoulders, Thorson continued to receive
    treatment from Dr. Colby for thoracic and cervical spasm, bilateral
    tendonitis,   and    lateral   epicondylitis    during    the    interval   between
    November 1996 and April 1998.
    In May 1998, Thorson began receiving treatment from Dr. Clarence
    Carlson, who ordered a functional capacity evaluation and recommended
    a psychiatric consultation to rule out any underlying mental disorder.
    The functional capacity evaluation performed on July 8 and 9, 1998
    documented Thorson’s difficulty with overhead lifts and sustained
    overhead work due to pain. The evaluator recommended frequent rest
    breaks     during    sustained      overhead      activities    and    work-station
    accommodations to avoid the need for floor-to-waist level lifting.
    On July 13, 1998, Thorson underwent a psychiatric evaluation by
    Dr. Karen Gosen.       Dr. Gosen diagnosed major depression “with sleep,
    appetite, energy, and mood changes,” and “chronic pain syndrome.” In
    August 1998, Dr. Carlson informed Thorson he believed she had
    fibromyalgia, and that she might benefit from chronic pain management.
    The only documented medical treatment Thorson received between
    August 1998 and May 1999 was for an injury to her right knee sustained
    during the functional capacity evaluation in July 1998.3
    3The knee injury was diagnosed as a meniscal tear and treated with surgery.
    The commissioner found this injury compensable, and it is not at issue in this appeal.
    5
    Thorson again consulted Dr. Colby for back spasms in May 1999.
    On July 23, 1999, Thorson filed two petitions for workers’ compensation
    benefits. The first petition alleged the July 1998 right leg injury. The
    second petition alleged Thorson was disabled at “various times” from
    1993 to 1999, and that she sustained a cumulative injury to her upper
    back, neck, shoulders, and arms “on or about July 20, 1999.”4
    Thorson returned to Dr. Carlson for treatment in January 2000.
    She described the pain in her neck, upper thoracic spine, shoulders, and
    arms as essentially unchanged, but reported increased symptoms in her
    elbows.     Dr. Carlson concluded Thorson was experiencing “low grade
    bilateral epicondylitis,” which he characterized as “an acute/new
    problem.” Dr. Carlson referred Thorson to Dr. Jeffrey Brault, who had
    experience in the treatment of chronic musculoskeletal and chronic pain
    disorders.       Dr. Brault diagnosed “chronic myalgic pain syndrome” in
    February 2000, prescribed an antidepressant, ordered physical therapy
    for the shoulder and neck symptoms, and directed a continuation of
    Thorson’s work restrictions.
    Prior to the arbitration hearing on her petitions for workers’
    compensation benefits, Thorson underwent a medical exam by Dr. Justin
    Ban.5     Dr. Ban diagnosed multiple work-related injuries: a surgically
    treated right medial meniscal tear, cumulative trauma disorder, chronic
    cervicothoracic strain/sprain, and chronic pain disorder.                      His report
    dated October 10, 2000 opined Thorson’s injuries caused a total whole-
    person work related impairment of sixteen percent, consisting of five
    4July   20, 1999 was the last day Thorson worked prior to filing the two petitions.
    5Thisexamination was requested by Thorson pursuant to Iowa Code section
    85.39 (1999) (authorizing claimants to obtain “a subsequent examination by a
    physician of [their] own choice” at the employer’s expense after the employer has
    obtained an evaluation of the claimant’s disability).
    6
    percent for the cervicothoracic spine condition, one percent for the right
    knee, and ten percent for the “chronic pain disorder associated with
    psychological factors and cumulative trauma disorder.”6                  As we have
    already noted, Dr. Ban’s report (the only extant medical opinion
    providing     a   permanent      impairment      rating    of   Thorson’s     claimed
    cumulative injury prior to the arbitration hearing) was excluded from
    evidence by the deputy, but this court ordered the agency to consider
    Dr. Ban’s opinion on remand.
    Larson sought and obtained leave of the commissioner on remand
    to develop and present medical evidence rebutting the opinions of
    Dr. Ban. This evidence included a January 2005 report from Dr. Donna
    Bahls, a board certified independent medical examiner. Dr. Bahls opined
    Thorson experienced “chronic myofascial pain which is diffuse but
    [incompatible with] the criteria for myofascial pain syndrome or
    fibromyalgia.”      Although Dr. Bahls believed work activities “could
    temporarily aggravate or cause [the] underlying condition to be more
    symptomatic,” she concluded work activities were not the cause of
    Thorson’s condition. Dr. Bahls opined Thorson suffered no work-related
    whole body impairment.
    To rebut Dr. Ban’s finding of psychological impairment, Larson
    also offered on remand a January 2005 medical report authored by
    Dr. Charles Wadle, a psychiatrist.             Dr. Wadle opined there was “no
    6The   hearing record did include other medical evidence supporting Thorson’s
    cumulative injury claim. For example, Dr. Colby reported in October 2000 it was
    probable that Thorson’s work activities at Larson were a substantial, but not
    necessarily the exclusive, factor causing the various conditions he treated in Thorson’s
    shoulder, upper extremities, and cervicothoracic spine. Dr. Colby further opined
    Thorson’s “work activities did cause this condition more or less continuously during the
    period 1992 to the present time . . . and will cause permanent impairment.” He did not,
    however, express an opinion as to whether such impairment had yet manifested, or, if it
    had, its extent.
    7
    discernable psychiatric diagnosis for [Thorson] at this time,” and
    therefore disputed Dr. Ban’s impairment rating.
    As Dr. Ban’s October 2000 opinion was quite dated by the time of
    the commissioner’s remand proceeding, Thorson also sought to present
    new medical evidence for the agency’s consideration. She underwent an
    examination by Dr. John Kuhnlein in March 2005.                        Dr. Kuhnlein
    diagnosed chronic trapezius and scapulothoracic pain, and attributed a
    three percent whole-body permanent impairment to it.                   He concluded
    work activities were a substantial, but not necessarily the exclusive
    cause of Thorson’s chronic pain and resulting impairment. Dr. Kuhnlein
    also allocated one percent whole-body permanent impairment to the right
    knee injury, but found no causal connection between Thorson’s work
    activities and her shoulder, foot, and low-back complaints.                   Thorson
    requested the commissioner to order Larson to pay for the Kuhnlein
    examination under Iowa Code section 85.39.
    In   his   remand      decision,    the   commissioner       found     Thorson
    sustained a work-related cumulative injury on April 26, 1996, the date
    Thorson returned to Dr. Colby for treatment of her shoulder, back, and
    elbow pain.7      The commissioner concluded Thorson’s claims were not
    barred by the two-year statute of limitations because Thorson did not
    know, nor should she have known, the conditions would have a
    permanent adverse impact on her employment until she received
    Dr. Ban’s report in 2000. The remand decision ordered Larson to pay
    7Larson   challenged this injury-date finding, claiming it had been deprived of
    notice and opportunity to be heard as to an injury date other than July 20, 1999, the
    cumulative injury date alleged in Thorson’s petition. The commissioner rejected
    Larson’s due process claim, however, reasoning Larson was given sufficient notice of
    potential alternative manifestation dates from Thorson’s pleading of a cumulative injury
    date of “on or about July 20, 1999,” and from Thorson’s lengthy medical and
    employment history disclosed in the course of the administrative proceeding.
    8
    medical and transportation benefits, temporary partial benefits for the
    periods of August 31, 1992 through September 22, 1992; October 2,
    1992 through October 12, 1992; April 26, 1996 through January 2,
    1997; and April 9, 1998 through December 21, 1998,8 and permanent
    partial disability benefits compensating for an industrial disability of
    twenty-five percent. In addition to the other relief granted, the remand
    decision ordered Larson to reimburse Thorson pursuant to Iowa Code
    section 85.39 for the full cost of Dr. Kuhnlein’s medical evaluation.
    Thorson requested a rehearing.          The commissioner subsequently
    issued a rehearing decision awarding Thorson additional temporary total
    disability benefits for an additional period from January 8, 2000 to
    January 11, 2000, and providing Larson’s obligation to pay permanent
    partial disability benefits should commence January 12, 2000. Larson
    also filed a motion for rehearing prompting a second rehearing decision
    which     reduced     the   amount      Larson       was   obligated    to   pay    for
    Dr. Kuhnlein’s examination.
    On judicial review the district court affirmed the remand decision
    in all respects.
    II.   Issues on Appeal.
    Larson     contends     several     errors    require     reversal    of    the
    commissioner’s remand decision.            Larson claims: (1) the finding of an
    injury date prior to July 20, 1999, and the award of temporary partial
    disability benefits are foreclosed by principles of issue preclusion, (2) its
    rights to reasonable notice and an opportunity to be heard were violated
    8As Thorson’s personnel records for 1992 were not in the record before the
    agency, the commissioner ordered Larson to pay temporary partial disability benefits for
    these periods, with the exact amount to be calculated by the parties. If the parties
    could not agree as to the amount of such benefits, they were directed by the remand
    decision to submit their calculations to the commissioner in furtherance of a
    supplemental ruling.
    9
    when the commissioner selected a cumulative injury date that is more
    than three years prior to the injury date alleged in Thorson’s petition,
    (3) Thorson’s cumulative injury claim is barred by the applicable statute
    of limitations, (4) the award of temporary partial benefits and of
    industrial disability benefits are not supported by substantial evidence,
    (5) the commissioner erred in awarding medical benefits under section
    85.27 for treatment rendered before the cumulative injury date, and (6)
    the commissioner erred in ordering Larson to pay for more than one
    examination of Thorson under section 85.39.
    III.   Scope of Review.
    Iowa Code chapter 17A governs the scope of our review in workers’
    compensation cases. Iowa Code § 86.26. It is well settled that “ ‘[t]he
    interpretation of workers’ compensation statutes and related case law
    has not been clearly vested by a provision of law in the discretion of the
    agency.’ ”   Lakeside Casino v. Blue, 
    743 N.W.2d 169
    , 173 (Iowa 2007)
    (citation omitted).   We therefore do not defer to the commissioner’s
    interpretation of the law. Id.; see Iowa Code § 17A.19(10)(c).
    Factual determinations in workers’ compensation cases, on the
    other hand, are “ ‘clearly vested by a provision of law in the discretion of
    the agency.’ ”   Mycogen Seeds v. Sands, 
    686 N.W.2d 457
    , 465 (Iowa
    2004) (citation omitted).   Accordingly, we defer to the commissioner’s
    factual determinations if they are based on “substantial evidence in the
    record before the court when that record is viewed as a whole.”        Iowa
    Code § 17A.19 (10)(f). “Substantial evidence” is:
    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.
    10
    Iowa Code § 17A.19(10)(f)(1).    Thus, when we review factual questions
    delegated by the legislature to the commissioner, the question before us
    is not whether the evidence supports different findings than those made
    by the commissioner, but whether the evidence “supports the findings
    actually made.” St. Luke’s Hosp. v. Gray, 
    604 N.W.2d 646
    , 649 (Iowa
    2000) (citing Kiesecker v. Webster City Custom Meats, Inc., 
    528 N.W.2d 109
    , 110 (Iowa 1995)).
    The application of the law to the facts is also an enterprise vested
    in the commissioner. Mycogen Seeds, 686 N.W.2d at 465. Accordingly,
    we reverse only if the commissioner’s application was “irrational, illogical,
    or wholly unjustifiable.” Id.; Iowa Code § 17A.19(10)(l). This standard
    requires   us   to   allocate   some   deference   to   the   commissioner’s
    determinations, but less than we give to the agency’s findings of fact.
    See Arthur E. Bonfield, Amendments to Iowa Administrative Procedure
    Act, Report on Selected Provisions to Iowa State Bar Association and Iowa
    State Government 70 (1998) (“[W]hen an agency is delegated discretion in
    applying a provision of law to specified facts the scope of review
    appropriately applied by courts must be deferential because the
    legislature decided that the agency expertness justifies vesting primary
    jurisdiction over that matter in the discretion of the agency rather than
    in the courts.”).
    We review constitutional claims de novo. Wright v. Iowa Dep’t of
    Corr., 
    747 N.W.2d 213
    , 216 (Iowa 2008).
    We review the commissioner’s determination on the statute of
    limitations issue for correction of errors at law.      Chapa v. John Deere
    Ottumwa Works, 
    652 N.W.2d 187
    , 189 (Iowa 2002).
    11
    IV.    Discussion.
    A.     Issue Preclusion. Larson raises two issue preclusion claims
    on appeal.9 First, Larson notes the commissioner’s appeal decision filed
    on March 26, 2001 observed that “Defendants would not have been
    reasonably put on notice by claimant’s discovery answer that [Thorson]
    was actually alleging a date of injury in 1992 or 1996.” Larson contends
    this language precluded a finding in the subsequent remand proceedings
    that Larson had sufficient notice of the April 26, 1996 cumulative injury
    date to satisfy the applicable due process standard.                Second, Larson
    asserts the commissioner was precluded on remand from finding
    Thorson was entitled to temporary partial disability benefits because the
    agency’s appeal decision had previously found Thorson failed to
    demonstrate eligibility for TPD benefits.
    We follow a well-established analytical framework in deciding
    whether a party is precluded from re-litigating an issue.                         The
    prerequisites for preclusion are:
    (1) the issue concluded must be identical; (2) the issue must
    have been raised and litigated in the prior action; (3) the
    issue must have been material and relevant to the
    disposition of the prior action; and (4) the determination
    made of the issue in the prior action must have been
    necessary and essential to the resulting judgment.
    Hunter v. Des Moines, 
    300 N.W.2d 121
    , 123 (Iowa 1981) (citation
    omitted).    Larson’s preclusion claims must fail because the subject
    issues were not decided in a “prior action.” The commissioner’s appeal
    decision and the remand decision are parts of a single action, not
    adjudications of consecutive actions in which the doctrine of issue
    9Thorson   contends Larson failed to argue preclusion before the commissioner on
    remand, and consequently failed to preserve the issue for our review. We nonetheless
    elect to decide them.
    12
    preclusion might have application. Cf. State v. Pexa, 
    574 N.W.2d 344
    ,
    347 (Iowa 1998) (holding the district court’s original decision, a decision
    on appeal, and the district court’s decision on remand is a “continuous
    judicial examination . . . in the same proceeding” for the purpose of
    evaluating whether jeopardy attaches to a criminal defendant).
    B.    Notice of Date of Injury. Larson next contends its right to
    due process was violated when the commissioner found a date of injury
    more than three years prior to the date alleged in Thorson’s petition. A
    proper understanding of this issue is informed by a review of this court’s
    decisions addressing the compensability of cumulative work-related
    injuries.
    We adopted the cumulative injury rule in McKeever Custom
    Cabinets v. Smith, 
    379 N.W.2d 368
     (Iowa 1985). By their very nature,
    cumulative injuries develop over time and eventually result in a
    compensable disability. McKeever, 379 N.W.2d at 373. Because such
    injuries develop gradually as a consequence of repetitive motion or
    overuse, the enterprise of determining the date when a cumulative injury
    “occurs” is typically a challenging task. Although it can be difficult to
    identify with precision, the date of cumulative injury is of critical
    importance in the determination of which of multiple employers and
    insurance carriers are “on the risk, whether notice of injury and claim
    were within the statutory period, whether statutory amendments were in
    effect, which wage basis applies, and many others.”       Oscar Mayer v.
    Tasler, 
    483 N.W.2d 824
    , 829 (Iowa 1992).         In McKeever, we held a
    cumulative injury “occurs” for limitation purposes when, “because of
    pain or physical inability, [the employee] can no longer work.”        379
    N.W.2d at 374.
    13
    We revisited the analytical framework for identifying a claimant’s
    date of cumulative injury in Tasler.      483 N.W.2d at 829.    Tasler, who
    performed various jobs requiring repetitive motion in Oscar Mayer’s
    packing plant, was repeatedly treated for neck, upper extremity, and
    back pain during the more than five years of her employment. Id. at 827.
    Despite her history of recurring medical treatment and multiple transfers
    to lighter-duty work stations during those years, Tasler apparently did
    not lose any time from work before the plant closed permanently on
    February 3, 1989.    Id. at 828.   Tasler subsequently filed five petitions
    seeking workers’ compensation benefits for work-related injuries on four
    separate injury dates. Id. at 825–27. The agency found Tasler failed to
    prove she suffered a compensable injury on any one of the four dates
    alleged in her petitions, but nonetheless found she had sustained a
    “cumulative, repetitive, overuse type of injury” which caused an
    industrial disability of fifteen percent on the date the plant closed. Id. at
    828. The employer sought judicial review of the agency’s date-of-injury
    finding, contending the plant closing date could not have been the date of
    injury because Tasler’s medical condition had not prevented her from
    working on or before that date. Id. The employer further asserted its
    right to due process was violated when the agency found an injury date
    that had not even been alleged by Tasler. Id.
    In upholding the commissioner’s finding of Tasler’s injury date, we
    relied upon the “manifestation” rule, which defines the date of injury as
    the date on which a “disability manifests itself.”    Id. at 829 (citing 1B
    Arthur Larson, Workers’ Compensation Law § 39.50 (1991)).                We
    concluded an injury is manifest on “ ‘the date on which both the fact of
    the injury and the causal relationship of the injury to the claimant’s
    employment would have become plainly apparent to a reasonable
    14
    person.’ ”    Id. (quoting Bellwood Nursing Home v. Indus. Comm’n, 
    505 N.E.2d 1026
    , 1029 (Ill. 1987)). The commissioner’s determination of the
    injury date “is entitled to a substantial amount of latitude” as it is an
    “inherently fact-based determination” derived from a multitude of factors.
    Id. We found substantial evidence supporting the selection of the plant
    closing date as Tasler’s date of injury. Id. at 830.
    We      rejected   Oscar   Mayer’s   due   process   challenge   to   the
    commissioner’s selection of an injury date that had not been alleged by
    Tasler. In disposing of the due process argument, we stated:
    due process requires that a party “be informed somehow of
    the issue involved in order to prevent surprise at the hearing
    and allow an opportunity to prepare. . . . The test is
    fundamental fairness, not whether the notice meets
    technical rules of common law pleading.”
    Id. at 828 (quoting Wedergren v. Bd. of Dirs., 
    307 N.W.2d 12
    , 16 (Iowa
    1981)).      We concluded Oscar Mayer was sufficiently alerted to the
    cumulative nature of Tasler’s claim because one of the five petitions
    attributed the claimed disability to a “gradual injury from skinning
    hams,” while another alleged an injury arising from “repetitive use and
    strain of [the claimant’s] back during [the] course of employment.” Id.
    Under the circumstances, we concluded Oscar Mayer had failed to
    demonstrate prejudice. Id.
    We again confronted an employer’s claim of inadequate notice of an
    alleged cumulative injury in University of Iowa Hospitals & Clinics v.
    Waters, 
    674 N.W.2d 92
     (Iowa 2004). Waters, who had been employed as
    a hospital custodian for nearly thirty years, filed two petitions for
    arbitration. Waters, 674 N.W.2d at 93. The first alleged he sustained a
    back injury on October 24, 1996 while pushing a loaded cart. Id. at 93–
    94. The second claimed another back injury occurred on June 16, 1997
    15
    as Waters was “lifting, carrying, and dumping heavy trash at work.” Id.
    at 94. When uncertainty arose during Waters’ deposition as to the date
    of injury, counsel disclosed his intention to amend the petition to allege
    the injury occurred on June 21, 1997, the last date Waters worked for
    the employer.      Id.   The commissioner found Waters sustained a
    cumulative back injury on his last day of work, and awarded permanent
    total disability benefits.   Id. at 94–95.   The district court reversed the
    agency’s decision, concluding the employer was prejudiced by Waters’
    change of theory from claims of two separate traumatic injuries to a
    claim of cumulative injury on a date not alleged in the petitions. Id. at
    95.
    In Waters, we noted “ ‘[a]n application for arbitration is not a
    formal pleading and is not to be judged by the technical rules of
    pleading.’ ” Id. at 96–97 (emphasis omitted) (quoting Coghlan v. Quinn
    Wire & Iron Works, 
    164 N.W.2d 848
    , 850 (Iowa 1969)).             In further
    elucidating this principle, we stated:
    “The petition for arbitration may state the claims in general
    terms and technical or formal rules of procedure need not be
    observed. The key to pleading in an administrative process
    is nothing more than opportunity to prepare and defend.
    The employer is to be afforded a substantive right to be at
    least generally informed as to the basic material facts upon
    which the employee relies as a basis for compensation.”
    Id. at 97 (quoting James R. Lawyer and Judith Ann Graves Higgs, Iowa
    Workers’ Compensation–Law & Practice § 21-7, at 231 (3d ed. 1999)
    (footnotes and internal quotations omitted)). We found this standard of
    notice was met by Waters’ “vague use of three gerunds (“lifting, carrying,
    and dumping”) [which] implie[d] his injury resulted from repetitive work-
    related behavior.” Id. at 98. In determining the adequacy of the notice of
    Waters’ claimed date of injury, we noted discovery should have informed
    16
    the employer of the cumulative nature of the injury, particularly in light
    of testimony asserting Waters requested a change of his work
    responsibilities in order to avoid the exertional activities thought to be
    exacerbating his low-back symptoms. Id. “Although a history of back
    problems does not always necessitate a cumulative injury finding . . . ,
    such a history should alert an employer to the possibility of a cumulative
    injury claim.” Id.
    With the principles established in McKeever, Tasler and Waters in
    mind, we now consider whether Larson’s right to due process was
    infringed by the agency’s finding that Thorson suffered a cumulative
    injury on April 26, 1996.    We first note Thorson’s petition undercuts
    Larson’s argument that it was unaware of the possibility of an injury
    prior to July 20, 1999. Thorson expressly alleged her injury occurred
    “cumulatively, gradually, and progressively,” and caused her to be
    disabled at “various times [from] 1993–1999.” Larson had a due process
    right to be “sufficiently apprised of the possibility that the cumulative
    injury doctrine might be relied upon.”      Tasler, 483 N.W.2d at 828
    (emphasis added). Thorson’s petition provided ample notice by expressly
    apprising Larson of a claim that Thorson’s injury arose cumulatively and
    produced disability at times before 1999.      Furthermore, Larson had
    actual notice of the long progression of Thorson’s developing chronic pain
    symptoms as a consequence of: (1) the enduring employer-employee
    relationship during which Thorson was assigned to light duty because of
    her ongoing physical symptoms; (2) Thorson’s petition alleging disability
    at various times from 1993 to 1999; and, (3) the employer’s access to
    Thorson’s medical records generated in the course of treatment of those
    symptoms long before July 20, 1999. On this record, we find no merit in
    Larson’s due process challenge.
    17
    C.     Statute of Limitations.       As Thorson had not been paid
    disability benefits for the claimed cumulative injury before the petition
    was filed, the pertinent statute of limitations for her claim is “two years
    from the date of the occurrence of the injury for which benefits are
    claimed. . . .” Iowa Code § 85.26(1). Consistent with this court’s prior
    decisions, Thorson is entitled to the benefit of the discovery rule, Herrera
    v. IBP, Inc., 
    633 N.W.2d 284
    , 287 (Iowa 2001), and the statute of
    limitations did not begin to run until she recognized, or should have
    recognized,    the   “ ‘nature,   seriousness   and   probable   compensable
    character’ ” of the disability. Orr v. Lewis Cent. Sch. Dist., 
    298 N.W.2d 256
    , 257 (Iowa 1980) (citation omitted); accord Herrera, 633 N.W.2d at
    287. Thorson’s knowledge of these three triggering factors may be actual
    or imputed from the record. Ranney v. Parawax Co., 
    582 N.W.2d 152
    ,
    154–55 (Iowa 1998).
    The commissioner found Thorson’s cumulative injury became
    manifest on April 26, 1996 because by that date she knew she had a
    chronic pain condition that was causally connected to her work
    activities.   Larson contends the petition filed on July 23, 1999 was
    therefore untimely because it was filed more than two years after the
    injury date. We disagree. The statute of limitations does not necessarily
    begin to run on the date the injury becomes manifest.            Herrera, 633
    N.W.2d at 288. In Herrera, we noted the discovery rule may cause the
    date of a cumulative injury’s manifestation to diverge from the date when
    the limitation period begins to run:
    [A] cumulative injury is manifested when the claimant, as a
    reasonable person, would plainly be aware (1) that he or she
    suffers from a condition or injury, and (2) that this condition
    or injury was caused by the claimant’s employment. Upon
    the occurrence of these two circumstances, the injury is
    deemed to have occurred. Nonetheless, by virtue of the
    18
    discovery rule, the statute of limitations will not begin to run
    until the employee knows that the physical condition is
    serious enough to have a permanent adverse impact on the
    claimant’s employment or employability, i.e., the claimant
    knows or should know the ‘nature, seriousness, and
    probable compensable character’ of his injury or condition.
    Id. (citing Orr, 298 N.W.2d at 257).
    Larson contends the court modified the Herrera formulation of the
    discovery rule in Chapa, 652 N.W.2d at 189. In Chapa, we restated the
    rule announced in Herrera that the statute of limitations in a cumulative
    injury case “does not begin to run until the worker recognizes, or should
    recognize, the ‘nature, seriousness and probable compensable character’
    of the disability.” 652 N.W.2d at 189 (quoting Orr, 298 N.W.2d at 257).
    We failed, however, in Chapa to quote language from Herrera which
    clearly communicated that a claimant is deemed to know the nature,
    seriousness and probable compensable character of an injury when she
    knows her physical condition is serious enough to have a permanent
    adverse impact on her employment or employability. See Herrera, 633
    N.W.2d at 288.
    Larson asserts our omission in Chapa of the “permanent adverse
    impact” language from Herrera is tantamount to a repudiation of the
    proposition that the limitations period does not begin to run until the
    claimant has knowledge of an injury’s permanent impact on her
    employment.    Our failure to repeat verbatim language from Herrera in
    Chapa should not be so understood. Indeed, we cited Herrera in Chapa,
    and gave no indication of a retreat from the earlier formulation of the
    discovery rule as it is applied in cumulative injury and other workers’
    compensation cases. Chapa, 652 N.W.2d at 189–90. We now clarify that
    our “shorthand” expression of the discovery rule in Chapa did not signal
    the court’s intent to reformulate the rule.
    19
    In his remand proceeding, the commissioner found Thorson was
    not aware of the nature, seriousness and probable compensable
    character of her injury before she filed her petitions on July 28, 1999.
    Larson challenges this finding, emphasizing Thorson experienced, and
    sought medical treatment for, pain in her neck, upper extremities, and
    back long before that date. Although the record could support a finding
    of an earlier discovery date, the finding made by the commissioner is
    supported by substantial evidence in the record.         Although Thorson
    claimed she was unable to take advantage of some overtime hours
    because of her chronic pain condition, she had not lost any regular
    hours of work and she was still working full-time with some overtime
    hours when she filed her petitions on July 28, 1999. Although light duty
    had been ordered by a medical provider, Thorson had been given neither
    permanent work restrictions nor a permanent physical impairment rating
    before that date.   Thus, we affirm the agency’s determination that
    Thorson’s claims were timely under the discovery rule.
    D.    Industrial Disability. On the subject of Thorson’s claimed
    industrial loss, the commissioner’s remand decision stated:
    The claimant is still employed at her old job. She has not
    suffered a loss of earnings as a result of work injury, other
    than lost overtime. She continues to suffer with pain in her
    neck and shoulder blades, muscle spasms in her shoulders,
    and pain in both elbows, especially when lifting, pulling,
    grasping, doing overhead work, reaching out, pushing or
    grasping, or pulling.      She has no permanent work
    restrictions, however. She has a rating of permanent partial
    impairment of five percent of the body as a whole from her
    chronic pain syndrome from Dr. Ban, and three percent of
    the body as a whole from Dr. Kuhnlein. Dr. Carlson rated
    her impairment as zero percent, as did Dr. Bahls.
    As a result of the work injury, there are many personal
    activities she can no longer perform. She was 44 years old
    at the time of the hearing; she is 48 now. Her work
    20
    experience is limited to manual labor, virtually all for one
    employer. She has only a high school diploma.
    Her ratings of impairment are low; she has no
    restrictions; she is still working at her old job and has not
    lost earnings other than lost overtime. Based on these and all
    appropriate factors of industrial disability, it is found that as
    a result of her work injury of April 26, 1996, the claimant
    has an industrial disability of 25 percent.
    (Emphasis added.)     Larson challenges the sufficiency of the evidence
    supporting the commissioner’s findings that Thorson (1) lost overtime
    wages as a consequence of her injury, and (2) sustained a twenty-five
    percent industrial disability.
    1. Lost overtime wages. Thorson testified that although voluntary
    overtime work was available to Larson’s employees, she did not take it (or
    took less than was available to her) on occasion during the year before
    the arbitration hearing because of her work restrictions, or because she
    felt unable to work the additional hours.      We conclude this testimony
    was minimally sufficient to constitute substantial evidence supporting
    the commissioner’s finding that Thorson lost some overtime earnings as
    a consequence of the cumulative injury.
    Although we have concluded the quantum of proof supporting the
    finding of a loss of overtime earnings is minimally sufficient to sustain it,
    our conclusion that no reversible error resulted from the commissioner’s
    consideration of that loss as a factor in the determination of industrial
    disability rests upon an additional ground. On judicial review we may
    grant relief to a party based on a finding of fact not supported by
    substantial evidence only when the agency’s action was “based upon”
    that determination of fact.      Iowa Code § 17A.19(10) (“The court shall
    reverse, modify, or grant other appropriate relief from agency action . . . if
    it determines that substantial rights of the person seeking judicial relief
    have been prejudiced because the agency action is . . . . (f) Based upon a
    21
    determination of fact . . . that is not supported by substantial evidence in
    the record when that record is viewed as a whole.”).
    We conclude Larson has failed to demonstrate the commissioner’s
    determination of Thorson’s industrial disability was based upon the
    finding that Thorson sustained claimed loss of overtime earnings. When
    viewed in the full context of the remand decision, we believe the
    commissioner’s passing references to Thorson’s claim of “lost overtime”
    were calculated primarily to acknowledge the cumulative injury did not
    cause a significant loss of earnings, a fact that tends to mitigate rather
    than increase industrial disability. Industrial disability is, of course, a
    measure of one’s loss of earning capacity in the competitive labor market.
    Acuity Ins. v. Foreman, 
    684 N.W.2d 212
    , 220 (Iowa 2004); Excel Corp. v.
    Smithart, 
    654 N.W.2d 891
    , 901 (Iowa 2002). Proof of an actual reduction
    in the claimant’s earnings is not essential to establish a loss of earning
    capacity.    St. Luke’s Hosp., 604 N.W.2d at 653.         As Larson has not
    shown the commissioner’s finding of a twenty-five percent industrial
    disability was substantially “based on” Thorson’s claimed loss of an
    undetermined amount of overtime earnings, we conclude Larson’s
    substantial rights were not prejudiced by the references to such evidence
    in the remand decision.
    2. Industrial disability rating. We now turn to Larson’s claim that
    the commissioner erred in awarding Thorson benefits for a twenty-five
    percent industrial disability. This issue is a mixed question of law and
    fact,   as   the   determination   of   industrial   disability   required   the
    commissioner to apply established law (the factors considered in
    determining whether an industrial disability occurred) to the facts. As
    Larson’s challenge to the agency’s industrial disability determination is a
    challenge to the agency’s application of law to the facts, we review this
    22
    issue under the “irrational, illogical, or wholly unjustifiable” standard.
    Meyer v. IBP, Inc., 
    710 N.W.2d 213
    , 218–19 (Iowa 2006).
    Larson contends the commissioner’s finding that Thorson suffered
    a twenty-five percent loss of earning capacity as a result of the injury was
    irrational, illogical, or wholly unjustifiable because “she has no
    restrictions, is working overtime, is working a second job, and earning
    more now than she ever earned.”        While the evidence highlighted by
    Larson was certainly relevant to the commissioner’s determination of
    industrial disability, and was in fact considered by the commissioner, it
    is not dispositive of the issue.   An assessment of industrial disability
    implicates “ ‘all the factors that bear on [the claimant’s] actual
    employability.’ ” Thilges v. Snap-On Tools Corp., 
    528 N.W.2d 614
    , 616
    (Iowa 1995) (quoting Guyton v. Irving Jensen Co., 
    373 N.W.2d 101
    , 104
    (Iowa 1985)) (emphasis added).      These factors include the claimant’s
    “age, education, qualification, experience, and inability due to injury to
    engage in the employment for which the claimant is fitted.” Id. (citing
    Doerfer Div. of CCA v. Nicol, 
    359 N.W.2d 428
    , 438 (Iowa 1984)). And as
    we have already noted, the fact that Thorson “was able to continue at
    h[er] job does not prove, as a matter of law, that [s]he has suffered no
    loss of earning capacity.” Second Injury Fund v. Hodgins, 
    461 N.W.2d 454
    , 456 (Iowa 1990).
    In arriving at the industrial disability determination of twenty-five
    percent, the commissioner considered Thorson’s modest functional
    impairment, as assessed by Dr. Ban and Dr. Kuhnlein, as well as the
    other relevant factors including Thorson’s age, educational background,
    qualifications for employment, work experience, motivation, loss of
    earnings, severity and situs of the injury, and history of work (light duty)
    restrictions.   Although factors emphasized by Larson (absence of
    23
    permanent work restrictions, continued full-time work including some
    overtime, and a history of increased actual earnings after the date of
    cumulative injury) certainly mitigated the extent of industrial disability in
    this case, other substantial evidence in the record supported the
    determination made by the agency in this case. Thorson’s age, her work
    experience limited to manual labor, her educational background, and the
    nature of her chronic pain condition are factors supporting the agency’s
    industrial disability determination.        In short, we cannot say the
    commissioner’s resolution of this issue on remand was irrational,
    illogical, or wholly unjustifiable, and we affirm on this issue.
    E.     Temporary     Partial   Disability   Benefits.        When it is
    “medically indicated that an employee is not capable of returning to
    employment substantially similar to the employment in which the
    employee was engaged at the time of injury, but is able to perform other
    work consistent with the employee’s disability,” a claim for temporary
    partial disability benefits may be made.      Iowa Code § 85.33(2).      Such
    benefits are intended to compensate an injured employee for a
    “temporary partial reduction in earning ability as a result of the
    employee’s temporary partial disability.” Id. The amount of temporary
    partial disability benefits owed by the employer is equal to “sixty-six and
    two-thirds percent of the difference between the employee’s weekly
    earnings at the time of injury, computed in compliance with section
    85.36, and the employee’s actual gross weekly income from employment
    during the period of temporary partial disability.” Id. § 85.33(4).
    Larson raises two challenges to the agency’s award of temporary
    partial disability benefits in this case.   First, Larson contends the law
    does not authorize an award of such benefits for periods before Thorson’s
    cumulative injury became manifest on April 26, 1996. Second, Larson
    24
    claims in the alternative that even if the law does authorize an award of
    permanent partial disability benefits to compensate a claimant for a
    diminution of earnings sustained prior to the manifestation date, the
    commissioner erred in awarding such benefits in this case because
    Thorson failed as a matter of law to meet her burden to prove the
    cumulative injury caused a decrease in her earnings sufficient to sustain
    the award. We address these arguments in turn.
    1. TPD benefits prior to date of manifestation. Iowa Code section
    85.33 provides, in relevant part:
    2.    “Temporary partial disability” or “temporarily, partially
    disabled” means the condition of an employee for
    whom it is medically indicated that the employee is not
    capable of returning to employment substantially
    similar to the employment in which the employee was
    engaged at the time of injury, but is able to perform
    other work consistent with the employee’s disability.
    “Temporary partial benefits” means benefits payable,
    in lieu of temporary total disability and healing period
    benefits, to an employee because of the employee’s
    temporary partial reduction in earning ability as a
    result of the employee’s temporary partial disability.
    Temporary partial benefits shall not be considered
    benefits payable to an employee, upon termination of
    temporary partial or temporary total disability, the
    healing period, or permanent partial disability,
    because the employee is not able to secure work
    paying weekly earnings equal to the employee’s weekly
    earnings at the time of injury.
    3.    If an employee is temporarily, partially disabled and
    the employer for whom the employee was working at
    the time of injury offers to the employee suitable work
    consistent with the employee’s disability the employee
    shall accept the suitable work, and be compensated
    with temporary partial benefits. If the employee refuses
    to accept the suitable work with the same employer,
    the employee shall not be compensated with temporary
    partial, temporary total, or healing period benefits
    during the period of the refusal. If suitable work is not
    offered by the employer for whom the employee was
    working at the time of the injury and the employee
    who is temporarily partially disabled elects to perform
    25
    work with a different employer, the employee shall be
    compensated with temporary partial benefits.
    Iowa Code § 85.33(2)–(3).
    Iowa Code section 85.32 provides that “except for injuries resulting
    in permanent partial disability, compensation shall begin on the fourth
    day of disability after the injury.” (Emphasis added.)10 Larson contends
    the agency erred in its remand decision by awarding temporary partial
    disability benefits for periods prior to April 26, 1996, and extending as
    far back as 1992.             As this argument challenges the agency’s
    interpretation of a provision of law, a function not clearly vested in the
    agency, Mycogen Seeds, 686 N.W.2d at 464, we are not constrained by
    deference     to   the   agency’s    decision    on    this   issue.      Iowa    Code
    § 17A.19(10)(c).
    When called upon to interpret a statute, we first determine
    whether the legislative enactment is ambiguous.                  If it is clear and
    unambiguous, “we give [the] statute a plain and rational meaning.” In re
    T.S., 
    705 N.W.2d 498
    , 502 (Iowa 2005) (citing ABC Disposal Sys., Inc. v.
    Dep’t of Natural Res., 
    681 N.W.2d 596
    , 603 (Iowa 2004)). If, on the other
    hand, the statute is ambiguous, we rely on well-established rules to aid
    our interpretation. Waukee v. City Dev. Bd., 
    590 N.W.2d 712
    , 717 (Iowa
    1999). A statute or rule “is ambiguous if reasonable minds could differ
    or be uncertain as to the meaning of the statute.” Carolan v. Hill, 
    553 N.W.2d 882
    , 887 (Iowa 1996).
    “Ambiguity may arise in two ways: (1) from the meaning of
    particular words; or (2) from the general scope and meaning of a statute
    when all its provisions are examined.”                Id. (citation omitted).       We
    conclude the phrase “after the injury” in section 85.32 is ambiguous
    10Ifthe period of incapacity extends beyond the fourteenth day following the date
    of injury, the claimant’s compensation for the third week of disability includes an
    additional amount equal to three days of compensation. See Iowa Code § 85.32.
    26
    when applied to cumulative injuries which develop gradually and
    progressively   rather   than    suddenly,   traumatically,   or   discretely.
    Reasonable minds could differ or be uncertain as to whether the phrase
    “after the injury” in a cumulative injury case means a temporary partial
    disability can be compensable only if it arises after the manifestation
    date, or whether it can be compensable even if it arises before the
    manifestation date as a consequence of a cumulative injury process
    which subsequently progresses to the point of manifestation.
    The ambiguity within the statute is made apparent in the
    arguments advanced in this case by Larson and Thorson.                Larson
    contends it can have no liability to Thorson for workers’ compensation
    benefits until after April 26, 1996, the manifestation date found by the
    commissioner. Thorson advances a much different interpretation of the
    phrase “after the injury” in section 85.32. She notes cumulative injuries
    develop gradually and progressively, and employees who suffer them will
    have periods of temporary, but progressively more profound, restriction
    or dysfunction until the injury becomes so disruptive as to satisfy the
    manifestation standard.         As the deterioration of their functioning
    advances toward manifestation, employees who experience cumulative
    trauma may require medical treatment, modifications of their work
    activities, and adjustments of their work schedules in order to continue
    their employment. Such employees may continue to work, as Thorson
    did, but experience temporary reductions of their earnings and require
    medical treatment long before their cumulative injuries are “manifest”
    under the standard established in our prior decisions.         Furthermore,
    Thorson posits the legislature’s use of the phrase “after the injury” rather
    than “after the date of injury” or “after the date of manifestation of the
    injury” leaves room for the likelihood that the drafters intended to
    27
    provide a remedy for temporary partial disability, if any, that occurs prior
    to the date of manifestation.
    We interpret the phrase “after the injury” in section 85.32 to
    permit an award of temporary partial disability benefits upon proof of a
    diminution of a claimant’s earnings during periods of temporary
    incapacity caused by a work-related condition which later manifests as a
    cumulative injury.   Our resolution of this issue is faithful to the well-
    established rule that chapter 85 is liberally construed in favor of the
    employee, with any doubt in its construction being resolved in the
    employee’s favor. Teel v. McCord, 
    394 N.W.2d 405
    , 406–07 (Iowa 1986).
    Invocation of this rule is appropriate under the circumstances presented
    here because we do not believe the General Assembly intended to deny a
    remedy under chapter 85 to employees who suffer a temporary reduction
    of earnings before a work-related cumulative injury progresses to the
    point of “manifestation” as we have defined it in our cases. We therefore
    affirm the commissioner’s interpretation of section 85.32 as authorizing
    an award of temporary partial disability benefits for periods prior to the
    date of manifestation upon proof that a claimant’s earnings were
    diminished temporarily as a result of a work-related cumulative injury
    process.
    2. Thorson’s proof of the TPD claim. Having concluded an award
    for temporary partial disability benefits may, upon proper proof, be
    established for periods prior to the date of a cumulative injury’s
    manifestation, we next address whether the record in this case contains
    substantial evidence supporting the commissioner’s award in this case.
    Larson contends the award is not supported in the record because,
    although Thorson testified she lost an unquantified amount of overtime
    wages in the year before the arbitration hearing held on November 21,
    28
    2000, she supplied no proof that the diminution of earnings claimed for
    the earlier relevant periods (prior to November 21, 1999) were caused by
    the work-related cumulative injury.11            Noting that some of Thorson’s
    claimed periods of temporary partial disability included holidays or
    vacations, Larson contends substantial evidence in the record does not
    support a finding that any diminution of overtime earnings was caused
    by the claimed cumulative injury.
    Thorson contends her proof of a causal connection between the
    claimed diminution of her earnings (a loss of overtime hours and related
    pay) and the cumulative injury is adequate in this case.                   First, she
    emphasizes that she worked under a medical restriction for light duty
    during the weeks for which she seeks temporary partial disability
    benefits. Second, Thorson relies on the medical records evidencing her
    long history of chronic pain symptoms, and her testimony establishing
    that she “turned down voluntary overtime” during the year prior to the
    arbitration hearing when she “didn’t think [she] could work past 3:30.”
    In the alternative, Thorson points out section 85.33 does not
    expressly require proof of a causal connection between her cumulative
    injury and the diminution of her earnings, and she asserts an award of
    temporary partial disability benefits may be supported by mere proof of a
    diminution of her earnings during weeks she worked under a light-duty
    restriction from her treating physician. In furtherance of her position on
    this point, Thorson notes section 85.33 provides a formula for calculating
    permanent partial disability benefits, but gives no indication that proof of
    a causal connection between a work-related cumulative injury and a
    reduction in earnings is required.
    11Only   one of the periods for which Thorson was awarded temporary partial
    disability benefits (January 8, 2000 to January 11, 2000) was within the year before the
    arbitration hearing.
    29
    Although we reject Thorson’s contention that she had no burden to
    produce evidence of a causal connection between the cumulative injury
    and the claimed diminution of earnings during the relevant weeks to
    support an award of temporary partial disability benefits under section
    85.33, we conclude she did produce substantial evidence of a causal
    connection in this case.    Thorson worked under a physician-imposed
    light-duty restriction during the relevant weeks, and the medical records
    clearly evidence she was suffering from chronic pain in multiple parts of
    her body throughout that time. This evidence is minimally sufficient to
    support a causal nexus between Thorson’s cumulative injury and the
    claimed diminution of her earnings for the relevant weeks.       Although
    Larson contends on appeal that Thorson might have worked less during
    some of those weeks not because of an injury, but because holidays,
    funerals, or vacations reduced her availability for work, the weight to be
    given such evidence was a matter for the commissioner to decide. We
    therefore affirm on this issue.
    F.    Medical Benefits Prior to Date of Manifestation. Similar
    to its challenge to the agency’s award of TPD benefits prior to the date of
    manifestation, Larson challenges the deputy commissioner’s award of
    medical benefits prior to the date of manifestation. The medical benefits
    statute, Iowa Code section 85.27(1), requires the employer to pay medical
    and transportation expenses “for all injuries compensable under this
    chapter.” Interpretation of section 85.27(1) has not clearly been vested
    in the discretion of the workers’ compensation commissioner, and we
    therefore owe no deference to the agency’s interpretation.      Iowa Code
    § 17A.19(10)(c).
    The plain language of section 85.27(1) requires the employer to pay
    for all medical costs incurred as a result of an injury compensable under
    30
    chapter 85.     Section 85.27(1) does not expressly limit the employer’s
    liability for medical costs to costs incurred following manifestation of a
    compensable     workers’   compensation    claim.   The   only    statutory
    requirement for compensability is that the treatment be “for” an injury
    compensable under the chapter. Work-related cumulative injuries are, of
    course, compensable under chapter 85, and consequently section
    85.27(1) requires the employer to compensate the employee for
    reasonable medical costs incurred as a result of such injuries.
    We find no language in the statute suggesting that an employer is
    without obligation to provide reasonable medical treatment for work-
    related health problems in advance of the date of manifestation of a
    cumulative injury.    We conclude the agency did not err in construing
    section 85.27(1) to require Larson to pay for medical treatment for
    Thorson’s work-related condition that later manifested as a cumulative
    injury.
    G.      Reimbursement for Multiple IMEs.         Iowa Code section
    85.39 provides, in relevant part, as follows:
    If an evaluation of permanent disability has been made by a
    physician retained by the employer and the employee
    believes this evaluation to be too low, the employee shall,
    upon application to the commissioner and upon delivery of a
    copy of the application to the employer and its insurance
    carrier, be reimbursed by the employer the reasonable fee for
    a subsequent examination by a physician of the employee’s
    own choice, and reasonable necessary transportation
    expenses incurred for the examination.
    Iowa Code § 85.39 (emphasis added).        Larson was ordered to pay for
    Dr. Ban’s October 2000 examination under this statute. Having paid for
    the prior examination, Larson contends the plain language of section
    85.39 precludes its liability for the subsequent examination by
    Dr. Kuhnlein.     We agree, and therefore reverse that part of the
    31
    commissioner’s remand decision ordering Larson to pay for the Kuhnlein
    examination.12
    V.     Conclusion.
    We affirm all aspects of the commissioner’s remand decision except
    for the order directing Larson to pay the cost of the Kuhnlein
    examination pursuant to section 85.39.
    AFFIRMED IN PART AND REVERSED IN PART.
    All justices concur except Wiggins and Baker, JJ., who take no
    part.
    12We  acknowledge the unusual circumstances which Thorson faced on remand
    in this case. Dr. Ban, who had provided Thorson’s only permanent impairment rating
    prior to the November 2000 arbitration hearing, was not available to update his report.
    Although Larson presented two new medical opinions for the commissioner’s
    consideration in the course of the remand proceeding, and Thorson had a strong
    interest in responding to this new evidence, the plain language of section 85.39 does
    not authorize the commissioner to require Larson to pay for a second examination in
    this case. Cf. State v. Kidd, 
    562 N.W.2d 764
    , 765 (Iowa 1997) (stating the word “an” as
    used in a criminal statute prohibiting unauthorized possession of “an offensive weapon”
    denotes a singular unit of prosecution). It is the legislature’s role to determine if
    claimants should be entitled to more than one examination at the employer’s expense
    under the statute.