   Decisions of the Nebraska Court of Appeals
822	21 NEBRASKA APPELLATE REPORTS



rights were not violated and that there was sufficient evidence
to support the trial court’s finding that Meints was guilty
on such counts beyond a reasonable doubt. We find that the
Beatrice City Code does not contradict state law and does not
criminalize conduct which is lawful under any state statute.
We also find that multiple prosecutions for the violations of
the Beatrice City Code do not violate the Double Jeopardy
Clause of the Fifth Amendment. We affirm the decision of the
district court.
                                                    Affirmed.



         Stacy Bolles,        wife of    Gregory Bolles,           deceased,
          on her behalf and on behalf of others eligible
               for benefits pursuant to   Neb. R ev. Stat.
                 § 48-122 et seq., appellee, v. Midwest
                   Sheet Metal Co., Inc., appellant.
                                    ___ N.W.2d ___

                        Filed March 11, 2014.     No. A-13-203.

 1.	 Workers’ Compensation: Judgments: Evidence: Appeal and Error.
      Under Neb. Rev. Stat. § 48-185 (Reissue 2010), a judgment of the Workers’
      Compensation Court may be modified, reversed, or set aside based on the ground
      that there is not sufficient competent evidence in the record to warrant the making
      of the order, judgment, or award.
 2.	 Workers’ Compensation: Appeal and Error. In determining whether to affirm,
      modify, reverse, or set aside a judgment of the Workers’ Compensation Court,
      an appellate court will not disturb the findings of fact of the trial judge unless
      clearly wrong.
 3.	 Workers’ Compensation: Evidence: Appeal and Error. In testing the suf-
      ficiency of the evidence to support the findings of fact by the Workers’
      Compensation Court, the evidence is considered in the light most favorable to
      the successful party, every controverted fact is resolved in favor of the successful
      party, and the successful party has the benefit of every inference that is reason-
      ably deducible from the evidence.
 4.	 Workers’ Compensation: Judgments: Evidence: Appeal and Error. Workers’
      Comp. Ct. R. of Proc. 11(A) (2011) requires the Workers’ Compensation Court to
      write decisions that provide the basis for a meaningful appellate review.
  5.	 ____: ____: ____: ____. Workers’ Comp. Ct. R. of Proc. 11(A) (2011) requires
      the judge to specify the evidence upon which the judge relies.
            Decisions   of the Nebraska Court of Appeals
	                   BOLLES v. MIDWEST SHEET METAL CO.	823
	                          Cite as 21 Neb. App. 822

 6.	 Workers’ Compensation. When a workers’ compensation claimant has suffered
     a heart attack, the foremost and essential problem is causation, that is, whether
     the employment caused an employee’s injury or death from a heart attack.
 7.	 Workers’ Compensation: Appeal and Error. The issue in regard to causation of
     an injury or disability is one for determination by the fact finder, whose findings
     will not be set aside unless clearly erroneous.
 8.	 Workers’ Compensation. In workers’ compensation cases, the heart injury cau-
     sation issue consists of two elements: (1) legal causation and (2) medical causa-
     tion. Under the legal test, the law must define what kind of exertion satisfies the
     test of arising out of the employment. Under the medical test, the doctors must
     say whether the exertion (having been held legally sufficient to support compen-
     sation) in fact caused the collapse.
 9.	 Workers’ Compensation: Proof. An exertion- or stress-caused heart injury to
     which the claimant’s preexisting heart disease or condition contributes is com-
     pensable only if the claimant shows that the exertion or stress encountered during
     employment is greater than that experienced during the ordinary nonemployment
     life of the employee or any other person.
10.	 ____: ____. If it is claimed that an injury was the result of stress or exertion in
     the employment, medical causation is established by a showing by the prepon-
     derance of the evidence that the employment contributed in some material and
     substantial degree to cause the injury.

  Appeal from the Workers’ Compensation Court: John R.
Hoffert, Judge. Affirmed.
  Darla S. Ideus, of Baylor, Evnen, Curtiss, Grimit & Witt,
L.L.P., for appellant.
  John C. Fowles, of Fowles Law Office, P.C., L.L.O., and
John F. Vipperman, of Anderson, Vipperman & Kovanda, for
appellee.
    Irwin, Pirtle, and Bishop, Judges.
    Irwin, Judge.
                     I. INTRODUCTION
   Gregory Bolles suffered a heart attack while working for
Midwest Sheet Metal Co., Inc. (Midwest), and died as a
result. Midwest appeals an award of the Nebraska Workers’
Compensation Court awarding benefits to Bolles’ wife, Stacy
Bolles (Stacy). On appeal, Midwest asserts that the compensa-
tion court’s award did not comply with Workers’ Comp. Ct.
R. of Proc. 11 (2011), because it contained insufficient fac-
tual findings, and asserts that the compensation court erred in
   Decisions of the Nebraska Court of Appeals
824	21 NEBRASKA APPELLATE REPORTS



finding that Stacy met her burden of proof with regard to both
factual and legal causation. We affirm.

                      II. BACKGROUND
                     1. Work and Incident
   The events giving rise to this cause of action occurred on
or about July 27, 2011. On that date, Bolles was employed
by Midwest as a foreman. Evidence adduced at trial indicated
that Bolles began work on that date at the Midwest shop in
Grand Island, Nebraska, at approximately 7 a.m. Bolles ran
some errands and picked up some necessary materials, and
Bolles and a coworker picked up a compressor for an air-
conditioning unit at a supply shop in Grand Island.
   There was conflicting evidence about what time Bolles and
the coworker arrived at the jobsite for that date, which was in
Harvard, Nebraska. There was evidence that they arrived at the
jobsite between 9:15 and 9:30 a.m.; there was also evidence
that it may have been as late as “around noonish.”
   Bolles and his coworkers were to replace the compres-
sor in an air-conditioning unit at a nursing home. The evi-
dence adduced at trial indicated that this was a big and time-­
consuming job. The air-conditioning unit was a large unit,
with sheet metal panels on the outside; was situated on two
metal rails on concrete slabs; and was located several feet off
the ground. The unit was located in a fenced area, with the
fencing mostly obscuring the unit from view and shielding it
from wind.
   When Bolles arrived at the worksite, some of the side panels
had been removed. Bolles began working with a screw gun to
detach other metal panels. Bolles then climbed up and into the
unit and worked inside of it for approximately 1 to 11⁄2 hours.
Bolles worked to remove bolts and flanges that kept the com-
pressor in place, and he utilized hand wrenches, ratchets, and
screwdrivers to remove the bolts and flanges. There was evi-
dence that Bolles spent the time inside the unit bent over and
squatting while removing the bolts and flanges.
   Once the compressor was disconnected, Bolles and a
coworker attached chains and manipulated the compressor out
        Decisions  of the Nebraska Court of Appeals
	              BOLLES v. MIDWEST SHEET METAL CO.	825
	                     Cite as 21 Neb. App. 822

of the air-conditioning unit while another coworker operated a
front-end loader to actually lift the compressor. The evidence
indicates that the compressor that had to be removed weighed
as much as 400 pounds. The evidence indicated that Bolles
“had to shove it around to clear the pipes” and guide it out
of the air-conditioning unit. The process of maneuvering the
compressor out of the air-conditioning unit took approximately
30 minutes.
   After the compressor was successfully lifted out of the air-
conditioning unit, it was placed on the ground. Bolles and
his coworkers then removed a variety of other parts, which
involved more use of handtools and wrenches.
   Parts were then attached to the new compressor, the new
compressor was lifted with the front-end loader, and Bolles
worked to guide the new compressor into the air-conditioning
unit. Bolles was again inside the air-conditioning unit to guide
the new compressor into place.
   Once the new compressor was inside the air-conditioning
unit, all of the bolts and flanges had to be replaced to connect
and secure the new compressor. During that time, Bolles was
inside the air-conditioning unit and, for the majority of the
time, bent over and using handtools to connect the bolts and
flanges. Connecting the new compressor took approximately
another hour.
   After the new compressor was connected and secured, it was
discovered that nitrogen was needed. Bolles left the worksite
and drove to meet another Midwest employee to pick up addi-
tional nitrogen. Bolles met the other employee approximately
halfway between Harvard and Hastings, Nebraska; the evi-
dence indicates that the distance between Harvard and Hastings
was approximately 18 miles, or approximately a 30-minute
drive. Bolles then returned to the worksite in Harvard. Bolles
then climbed back up on the air-conditioning unit and worked
on reattaching the sheet metal panels on the outside of the unit.
Bolles was replacing screws.
   A coworker estimated that Bolles had been back at the
worksite for anywhere from 15 minutes to 1 hour before he
suffered the heart attack. Bolles collapsed and fell from the
   Decisions of the Nebraska Court of Appeals
826	21 NEBRASKA APPELLATE REPORTS



air-conditioning unit. Evidence adduced at trial indicates that
an ambulance was dispatched to the worksite at approximately
4:20 p.m. Bolles subsequently died.
                      2. Weather Conditions
    Evidence adduced at trial demonstrated that the date of this
incident, July 27, 2011, was an “extremely hot” day. One of
Bolles’ coworkers testified that it was “[p]robably one of the
hottest days of the year” and that there was “[n]o wind” on
that date. He testified that it was “pretty nasty” outside and that
it felt “very” humid. He also testified that “[t]here was no air
flow in” the area where the air-conditioning unit was located
and that there was no shade where Bolles would have been
working on the air-conditioning unit.
    One of Bolles’ coworkers testified that Bolles had worked
“pretty much” the whole time that he was at the jobsite,
although the workers “took a break and stood in the shade a
little bit and drank a little water” on a couple of occasions.
Additionally, the work on preparing the new compressor to
be installed was performed in a shaded area. The evidence
indicates that when Bolles left the worksite to get nitrogen, he
drove in an air-conditioned company truck.
    One of Bolles’ coworkers testified that it was “probably
95 to a hundred” degrees on the date in question. There was
evidence adduced concerning the actual meteorological con-
ditions on the date in question, with data presented from
Grand Island, Hastings, and Clay Center, Nebraska, all in the
geographic vicinity of Harvard. The air temperature in Grand
Island between 1 and 6 p.m. on the date in question was con-
sistently between 88 and 89 degrees, which, combined with
relative humidity, yielded heat index values of approximately
100 degrees. The air temperature in Hastings between 1 and 6
p.m. on the date in question was consistently between 87 and
89 degrees. A heat index chart indicates that the heat index val-
ues in Hastings during that time would have been between 90
and 100 degrees. The air temperature in Clay Center between
1 and 6 p.m. on the date in question was consistently between
87 and 90 degrees, with heat index values between 93 and 102
degrees. The evidence indicates that the heat index numbers
         Decisions of the Nebraska Court of Appeals
	              BOLLES v. MIDWEST SHEET METAL CO.	827
	                     Cite as 21 Neb. App. 822

reflected in charts in the record were likely lower than the
actual heat index values, because the charts included in the
record were based on shaded conditions and because the actual
heat index values would be higher in direct sunlight; there was
testimony that direct sunlight could actually increase the index
values by up to 15 degrees.
                      3. Medical Evidence
   The evidence adduced at trial demonstrated that Bolles had
a prior history of cardiac health issues. He had suffered a prior
heart attack in May 2008, which had resulted in angioplasty
and insertion of a stent. Stacy testified that Bolles had suffered
from high blood pressure and high cholesterol and that he had
been a smoker. She also testified that although he exercised
for a couple of months after the 2008 heart attack, he then
stopped regularly exercising.
   Bolles’ daughter testified that Bolles was not involved in
aerobic activities. She testified that Bolles liked to sit on the
couch and watch television and that she would not have called
him an “active person outside of work.” She testified that he
did not take out the garbage or mow the yard. Bolles’ son testi-
fied similarly.
   There were two medical expert opinions presented to the
compensation court. Stacy presented the opinion of Dr. Vincent
Di Maio, while Midwest presented the opinion of Dr. Michael
Del Core. These two medical expert opinions differed on the
question of whether Bolles’ work on the date in question con-
stituted a material and substantially contributing factor to his
heart attack and death.
   Dr. Di Maio’s report indicates that he reviewed depositions
of Bolles’ coworkers, climatological data, Bolles’ medical
records, and the ambulance records from the date in question.
Dr. Di Maio noted the work performed by Bolles on the date
in question, as well as the heat and humidity on the date in
question. He opined that the stress of working in direct sun-
light and the high temperatures and humidity on the date in
question were contributing causes to Bolles’ heart attack. He
opined that “[t]he elevated temperature and humidity put stress
on [Bolles’] heart as it tried to counteract the environmental
   Decisions of the Nebraska Court of Appeals
828	21 NEBRASKA APPELLATE REPORTS



factors and maintain normal body temperature.” Dr. Di Maio
opined that Bolles’ “body would have taken steps to prevent
developing severe hyperthermia” and that “[a] large portion of
his blood supply would have been shuttled to vascular com-
plexes under the skin.” He opined that Bolles’ “[h]eart rate
and stroke volume would have been elevated” and that “[t]he
strain on the heart would have been sufficient to aggravate
an existing heart disease and cause death.” Thus, he opined
that Bolles’ “working in an environment of elevated tem-
perature and humidity was a material and substantial cause in
his death.”
   Dr. Del Core’s report indicates that he reviewed Stacy’s
deposition, Bolles’ medical records, weather data, and Dr.
Di Maio’s report. Dr. Del Core placed emphasis on Bolles’
medical history and noted that “[h]is blood pressure and cho-
lesterol were not well controlled, he continued to smoke and
he appeared non-compliant with his medications.” He also
placed emphasis on the evidence that Bolles had spent some
amount of time in an air-conditioned vehicle prior to the heart
attack. He opined that 15 to 20 minutes of work after being
in the air-conditioned vehicle “is simply not enough time to
cause an increase in body temperature sufficient to contribute
to his heart attack.” He indicated that he could not “say with
any degree of medical certainty that . . . Bolles’ activity on
June [sic] 27 was a significant factor.” He opined that Bolles’
preexisting medical conditions and risk factors “materially and
substantially contributed to [his] fatal heart attack” and that he
“[did] not believe heat or humidity on that day contributed to
his fatal heart attack.”
                           4. Award
   The compensation court noted in its award that the parties
had stipulated to Bolles’ employment and his average weekly
wage. The court noted the specific applicable case law in
Nebraska concerning recovery of benefits in compensation
cases involving heart attacks suffered at work. The court noted
the dual issues of legal and medical causation. The court cited
numerous authorities and discussed the standards applicable to
legal and medical causation in such cases.
        Decisions  of the Nebraska Court of Appeals
	              BOLLES v. MIDWEST SHEET METAL CO.	829
	                     Cite as 21 Neb. App. 822

   The compensation court also made a number of specific
factual findings and findings regarding credibility of witnesses
in its award. The court made findings about the specific work
performed by Bolles on the date in question and about the
weather conditions on the date in question. The findings are
consistent with the above factual background, including find-
ings about Bolles’ use of various handtools, in a bent-over
position inside the air-conditioning unit, in direct sunlight
and without airflow, and on a date on which the heat index
value “hovered around 100 [degrees] or more” and may have
“exceeded 100 degrees.” The court also made factual findings
about Bolles’ nonemployment life and activities, concluding
that Bolles lived a largely sedentary life, again consistent with
the above factual background.
   The compensation court concluded that there had been suffi-
cient evidence adduced to demonstrate that Bolles’ employment
life involved greater exertion and stress than he experienced in
his nonemployment life. The court also concluded that the
work activities on the date in question were greater than that
experienced in the ordinary nonemployment life of an average
person. The court thus concluded that sufficient evidence had
been adduced to demonstrate legal causation.
   The compensation court evaluated the conflicting medi-
cal expert opinions. The court made specific findings con-
cerning some of Dr. Del Core’s conclusions, noting that Dr.
Del Core’s emphasis on concerns about whether Bolles was
sufficiently caring for his own “physical well-being” was not
shared by a cardiologist who had examined Bolles approxi-
mately 3 months prior to this heart attack and had concluded
that “‘if [Bolles] continue[d] to do well,’” the cardiologist
would start seeing Bolles only on an annual basis, rather
than twice a year. The court did not find this determina-
tive, but did note that it impacted the weight to be given to
Dr. Del Core’s opinions. The compensation court also noted
that Dr. Del Core had emphasized whether Bolles had been
performing work exertion which was greater than his normal
work exertion, and it noted some perceived inconsistencies in
Dr. Del Core’s deposition testimony concerning whether the
   Decisions of the Nebraska Court of Appeals
830	21 NEBRASKA APPELLATE REPORTS



heat and humidity were contributing factors or may have been
contributing factors.
   The compensation court made a credibility determination
that Dr. Di Maio’s expert opinion “enjoys more persuasive
value” and found that although it, too, had some shortcomings,
“the Court [found] his overall opinion to be convincing.” The
court thus concluded that there had been sufficient evidence
adduced to demonstrate medical causation.
   Having found sufficient evidence to support findings of both
legal and medical causation, the compensation court awarded
benefits. This appeal followed.

               III. ASSIGNMENTS OF ERROR
   On appeal, Midwest asserts that the compensation court’s
award did not satisfy rule 11 and that the court erred in find-
ing sufficient evidence to support findings of legal and medi-
cal causation.

                          IV. ANALYSIS
   Midwest asserts that the compensation court failed to pro-
vide a well-reasoned opinion under rule 11 because the court
did not make sufficient factual findings to support its conclu-
sions about causation. Midwest also asserts that the court
erred in finding sufficient evidence to support a finding
of both legal and medical causation. We find no merit to
either assertion.
   [1] Under Neb. Rev. Stat. § 48-185 (Reissue 2010), a judg-
ment of the Workers’ Compensation Court may be modified,
reversed, or set aside based on the ground that there is not suf-
ficient competent evidence in the record to warrant the making
of the order, judgment, or award. Pearson v. Archer-Daniels-
Midland Milling Co., 285 Neb. 568, 828 N.W.2d 154 (2013);
Roness v. Wal-Mart Stores, 21 Neb. App. 211, 837 N.W.2d
118 (2013). Competent evidence means evidence that tends to
establish the fact in issue. Id.
   [2,3] In determining whether to affirm, modify, reverse, or
set aside a judgment of the Workers’ Compensation Court,
an appellate court will not disturb the findings of fact of the
        Decisions of the Nebraska Court of Appeals
	             BOLLES v. MIDWEST SHEET METAL CO.	831
	                    Cite as 21 Neb. App. 822

trial judge unless clearly wrong. Roness v. Wal-Mart Stores,
supra. See Hynes v. Good Samaritan Hosp., 285 Neb. 985, 830
N.W.2d 499 (2013). In testing the sufficiency of the evidence
to support the findings of fact by the Workers’ Compensation
Court, the evidence is considered in the light most favorable
to the successful party, every controverted fact is resolved in
favor of the successful party, and the successful party has the
benefit of every inference that is reasonably deducible from
the evidence. Roness v. Wal-Mart Stores, supra. See Pearson v.
Archer-Daniels-Midland Milling Co., supra.
                     1. Rule 11 Challenge
   Midwest first asserts that the the compensation court failed
to provide a well-reasoned opinion under rule 11 because the
court did not make sufficient factual findings to support its
conclusions about causation. We disagree.
   [4,5] Rule 11(A) requires the Workers’ Compensation Court
to write decisions that “provide the basis for a meaningful
appellate review.” Jurgens v. Irwin Indus. Tool Co., 20 Neb.
App. 488, 825 N.W.2d 820 (2013). In particular, rule 11(A)
requires the judge to “specify the evidence upon which the
judge relies.” Jurgens v. Irwin Indus. Tool Co., supra.
   In the present case, Midwest asserts that the compensation
court did not make specific findings about precisely how long
Bolles spent working in the heat and humidity on the date in
question, how much of the time was in direct sunlight, the
length of time spent in the air-conditioned truck while get-
ting nitrogen shortly before the heart attack, and the length
of time and duties performed after he returned and before the
heart attack.
   Although the compensation court did not make specific
findings on each of these points, the court did make factual
findings concerning the work performed by Bolles on the date
in question. The court made specific findings concerning the
nature of the work as requiring the removal of the bolts and
flanges with handtools, being inside the air-conditioning unit,
being in a bent-over position, and being “essentially performed
in the direct sun with little to no shade.” Those findings are
   Decisions of the Nebraska Court of Appeals
832	21 NEBRASKA APPELLATE REPORTS



all consistent with evidence adduced at trial, as set forth in the
above factual background.
   The compensation court made specific findings that Bolles
worked in this fashion for 1 to 11⁄2 hours during the portion
of the job that involved removing the old compressor. The
court made specific findings that the old compressor weighed
“approximately 350 pounds” and was located in an area limit-
ing exposure to wind. The court made specific findings that
Bolles also engaged in “manual manipulation of the compres-
sor” as it was being lifted out of the air-conditioning unit
with a front-end loader. The court made specific findings that
the old compressor was placed on the ground, that additional
components were removed, and that Bolles engaged in similar
activities all over again in placing the new compressor in place
and reattaching the bolts and flanges with handtools.
   The court also made specific findings that it found Dr.
Di Maio’s report and conclusions to be more persuasive and
more credible than Dr. Del Core’s report and conclusions. Dr.
Di Maio’s report specifically indicated that he had reviewed
depositions of Bolles’ coworkers, as well as medical records,
climatological data, and the ambulance records in reaching his
opinions and conclusions.
   The compensation court’s award in this case provides suffi-
cient detail and explanation of how and why the court reached
its decision to allow meaningful review. The court sufficiently
specified the facts and evidence upon which it based its deci-
sion. We find no merit to the assertion that this award did not
comply with rule 11.
                   2. Sufficiency of Evidence
                          on Causation
   Midwest next asserts that the compensation court erred in
finding that sufficient evidence had been adduced to demon-
strate both legal and medical causation. We disagree.
   [6,7] When a workers’ compensation claimant has suffered
a heart attack, the foremost and essential problem is causation,
that is, whether the employment caused an employee’s injury
or death from a heart attack. Zessin v. Shanahan Mechanical
& Elec., 251 Neb. 651, 558 N.W.2d 564 (1997); Rosemann
        Decisions  of the Nebraska Court of Appeals
	              BOLLES v. MIDWEST SHEET METAL CO.	833
	                     Cite as 21 Neb. App. 822

v. County of Sarpy, 237 Neb. 252, 466 N.W.2d 59 (1991).
See, also, Toombs v. Driver Mgmt., Inc., 248 Neb. 1016, 540
N.W.2d 592 (1995). The issue in regard to causation of an
injury or disability is one for determination by the fact finder,
whose findings will not be set aside unless clearly erroneous.
Zessin v. Shanahan Mechanical & Elec., supra; Leitz v. Roberts
Dairy, 237 Neb. 235, 465 N.W.2d 601 (1991).
   [8] In workers’ compensation cases, the heart injury cau-
sation issue consists of two elements: (1) legal causation
and (2) medical causation. Zessin v. Shanahan Mechanical
& Elec., supra; Toombs v. Driver Mgmt., Inc., supra; Leitz v.
Roberts Dairy, supra. Under the legal test, the law must define
what kind of exertion satisfies the test of “arising out of the
employment.” Id. Under the medical test, the doctors must say
whether the exertion (having been held legally sufficient to
support compensation) in fact caused the collapse. Id.
                       (a) Legal Causation
   [9] When a preexisting disease or condition is present, the
Nebraska Supreme Court has adopted the following test for
legal causation: An exertion- or stress-caused heart injury to
which the claimant’s preexisting heart disease or condition
contributes is compensable only if the claimant shows that the
exertion or stress encountered during employment is greater
than that experienced during the ordinary nonemployment life
of the employee or any other person. Id.
   In the present case, there was evidence adduced to demon-
strate that Bolles arrived at the worksite in Harvard between
9:15 and 9:30 a.m. Bolles, along with two coworkers, engaged
in physical labor to remove a 350- or 400-pound compressor
from an air-conditioning unit, which included climbing up into
the unit and using handtools for 1 to 11⁄2 hours in a bent-over
position to remove numerous bolts and flanges, physically
helping to guide and maneuver the compressor out of the air-
conditioning unit as it was lifted by a front-end loader, remov-
ing additional parts while the compressor was on the ground,
attaching parts to a new compressor, climbing up into the unit
again and physically helping to guide and maneuver the new
compressor into the air-conditioning unit as it was lifted by a
   Decisions of the Nebraska Court of Appeals
834	21 NEBRASKA APPELLATE REPORTS



front-end loader, and using handtools for at least another hour
in a bent-over position to replace numerous bolts and flanges.
There was evidence to suggest that Bolles performed much of
this work in direct sunlight, that the air temperature and the
heat index values were extremely high throughout the day in
question, and that there was little or no airflow where Bolles
was working. Although Bolles left the jobsite and traveled in
an air-conditioned vehicle to get nitrogen, he had returned to
the worksite and worked with handtools to replace metal sheet-
ing for anywhere from 15 minutes to 1 hour immediately prior
to the heart attack.
   The evidence adduced at trial demonstrated that in his non-
employment life, Bolles did not exert himself. The testimony
established that he did not engage in aerobic activity, did not
perform tasks such as mowing or taking the garbage out, and
generally preferred to sit on the couch and watch television.
Although he enjoyed watching his son play baseball, there was
evidence that he primarily sat in the bleachers during games
and that many of the games were during evening hours and not
in the hottest portions of the day.
   We determine that the compensation court was not clearly
wrong in concluding that Bolles’ work activities on the date
in question constituted an exertion or stress greater than that
experienced during the ordinary nonemployment life of Bolles
or any other person. Thus, there is no merit to Midwest’s asser-
tion that the evidence was insufficient to support the court’s
conclusion on legal causation.

                      (b) Medical Causation
   [10] While legal causation is established by satisfying the
“stress greater than nonemployment life” test, a claimant
must still establish medical causation. Zessin v. Shanahan
Mechanical & Elec., 251 Neb. 651, 558 N.W.2d 564 (1997).
If it is claimed that an injury was the result of stress or exer-
tion in the employment, medical causation is established by a
showing by the preponderance of the evidence that the employ-
ment contributed in some material and substantial degree to
cause the injury. Id.; Leitz v. Roberts Dairy, 237 Neb. 235, 465
        Decisions of the Nebraska Court of Appeals
	             BOLLES v. MIDWEST SHEET METAL CO.	835
	                    Cite as 21 Neb. App. 822

N.W.2d 601 (1991). See, also, Toombs v. Driver Mgmt., Inc.,
248 Neb. 1016, 540 N.W.2d 592 (1995).
   To establish medical causation, Stacy introduced the expert
medical opinion of Dr. Di Maio. As noted, in his report, Dr.
Di Maio indicated that he had reviewed depositions of Bolles’
coworkers, climatological data, Bolles’ medical records, and
the ambulance records from the date in question. Dr. Di Maio
noted the work performed by Bolles on the date in question, as
well as the heat and humidity on the date in question.
   Dr. Di Maio opined that the stress of working in direct
sunlight and the high temperatures and humidity on the date
in question were a contributing cause to Bolles’ heart attack
and that “[t]he elevated temperature and humidity put stress on
[Bolles’] heart as it tried to counteract the environmental fac-
tors and maintain normal body temperature.”
   Dr. Di Maio opined that Bolles’ “body would have taken
steps to prevent developing severe hyperthermia” and that “[a]
large portion of his blood supply would have been shuttled to
vascular complexes under the skin.” He opined that Bolles’
“[h]eart rate and stroke volume would have been elevated”
and that “[t]he strain on the heart would have been sufficient
to aggravate an existing heart disease and cause death.” Dr.
Di Maio specifically opined that Bolles’ “working in an envi-
ronment of elevated temperature and humidity was a material
and substantial cause in his death.”
   Although Midwest introduced an opposing expert medical
opinion, the compensation court made specific findings and
specifically concluded that it found Dr. Di Maio and his opin-
ions to be more credible and entitled to more weight. Thus,
the court found that, according to Dr. Di Maio’s findings and
opinion, sufficient evidence had been adduced to demonstrate
medical causation. As previously stated, causation is a factual
issue to be determined by the trier of fact, whose determina-
tion will not be reversed unless it is clearly erroneous. Zessin
v. Shanahan Mechanical & Elec., supra. See Leitz v. Roberts
Dairy, supra.
   We conclude that the compensation court did not clearly err
in finding that the evidence was sufficient to establish medical
   Decisions of the Nebraska Court of Appeals
836	21 NEBRASKA APPELLATE REPORTS



causation. Midwest’s assignment of error to the contrary is
without merit.
                      V. CONCLUSION
   We find no merit to Midwest’s assertions on appeal that the
compensation court failed to provide a well-reasoned opinion
under rule 11 and that the evidence was insufficient to demon-
strate legal and medical causation. We affirm.
                                                    Affirmed.
