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     WILLIAM D. HART v. FEDERAL EXPRESS
            CORPORATION ET AL.
                  (SC 19523)
 Rogers, C. J., and Palmer, Zarella, Eveleigh, McDonald, Espinosa and
                             Robinson, Js.
    Argued December 14, 2015—officially released April 19, 2016

  David A. Kelly, with whom was Ryan D. Ellard, for
the appellants (defendants).
  Robert B. Keville, with whom was Roger T. Scully,
for the appellee (plaintiff).
                         Opinion

   ESPINOSA, J. This case arises from an incident in
which the plaintiff, William D. Hart (claimant), allegedly
suffered heart problems and associated psychological
injuries during the course of his employment as a cou-
rier for the named defendant, Federal Express Corpora-
tion     (FedEx).     The    Workers’      Compensation
Commissioner for the Second District (commissioner)
found that both the claimant’s physical and psychologi-
cal injuries were compensable under the Workers’ Com-
pensation Act (act), General Statutes § 31-275 et seq.,
and awarded him total incapacity benefits covering a
period of approximately forty-seven weeks. FedEx and
its claims administrator, the defendant Sedgwick CMS,
Inc., appeal from the decision of the Workers’ Compen-
sation Review Board (board) upholding the commis-
sioner’s findings and award. On appeal, the defendants
contend that neither the claimant’s physical nor his
psychological injuries are compensable under the act
and, in the alternative, that the commissioner’s award
was excessive. We disagree and, accordingly, affirm the
decision of the board.
  The following facts, as found by the commissioner,
and procedural history are relevant to the disposition
of this appeal. The claimant was employed by FedEx
from 1987 through September 15, 2009, the claimed date
of injury at issue in this case. The claimant worked as
a courier, delivering packages to customers along a
specified route. His daily job duties involved inspecting
his vehicle and inventorying and loading parcels onto
the vehicle. After doing so, he would confer with his
manager about the number of stops to be made, and
then drive from the FedEx terminal in the town of
Norwich to his assigned delivery territory in the town of
Stonington, including the Mystic and Pawcatuck areas.
  Once in his delivery area, the claimant would spend
the first part of the morning, until 10:30 a.m., making
priority overnight deliveries in Mystic. He would then
begin making the next round of morning deliveries in
and around the borough of Stonington (borough), to
be completed by noon. He would then proceed into
Pawcatuck and on into North Stonington. After com-
pleting all of his deliveries and pickups for the day, the
claimant would return to Norwich, stopping at a gas
station to top off his truck.
  The claimant, who was forty-seven years old on the
claimed date of injury, was avid about physical fitness.
He would rise each day at 4 a.m. and work out at the
gym for as long as two hours before going to work. He
engaged in intense gym workouts, including weightlift-
ing and ‘‘ ‘cardio’ ’’ components, as many as six times
per week, and he also went running approximately three
times each week.
  The claimant’s job requirements were demanding as
well. His delivery area encompassed the tourist attracti-
ons of Mystic; Pawcatuck, which is the gateway to the
beaches in Westerly, Rhode Island; and the heavily trav-
eled Route 1 corridor between those towns. Daytime
driving in this area, particularly during the summer tour-
ist season, is challenging, and is complicated by having
to cross the Route 1 drawbridge over the Mystic River.
The claimant’s workday averaged ten to twelve hours.
Nevertheless, he was, by all accounts, a dedicated and
hardworking employee who took great satisfaction in
his job. He received a notable award for his service in
2004, and had an unblemished employment record prior
to 2009.
  In early 2009, however, the claimant came under the
direction of a new manager and the demands of his
job began to escalate. His delivery area was enlarged,
increasing the number of stops and the associated driv-
ing time. The claimant’s typical ‘‘ ‘stop count’ ’’ climbed
to 12.5 per hour, leaving less than five minutes on aver-
age for him to drive to and complete each delivery. The
claimant asked his managers for help, but was told that
nothing could be done.
   FedEx policy provides that each driver receive a one-
half hour daily lunch break. FedEx also has strict stan-
dards for the timeliness of deliveries, however, and
drivers are judged and graded on their ability to satisfy
FedEx customers and complete assigned stops by the
appointed deadlines. Owing to the increasing size of
his delivery area and the traffic demands of the tourist
season, during the summer of 2009, the claimant often
was unable to find time even for bathroom breaks or
his lunch break before 4:30 p.m. The claimant’s manag-
ers were made aware that his route had become
unworkable, but they took no steps to mitigate the
situation and, according to the claimant, continued to
increase the demands of his route.
   At the end of one shift in June, 2009, the claimant
made his usual refueling stop in Norwichtown before
returning to the nearby FedEx terminal. After refueling,
however, he failed to secure the cap properly on the
truck’s fill pipe. When he arrived at the terminal yard,
he smelled diesel fuel and realized that a small amount
of fuel had spilled out of the fill pipe. The claimant
reported the spillage to the office manager, who
promptly called the fire department and the police. The
incident ultimately involved the intervention of a haz-
ardous materials team and federal occupational health
officials. The claimant, who believed that FedEx had
overreacted, was sent home. Upon returning to work
for his next shift, the claimant was reprimanded for the
fuel spill incident. On June 24, 2009, he received a writ-
ten warning regarding that incident. At the same time,
FedEx gave the claimant another written warning, stat-
ing that, when he took time off in May, 2009, he had
exceeded his allotment of scheduled time off. The
claimant testified that this overage was the result of
how FedEx chose to account for five days he had been
out of work when his mother died, classifying only three
of the five days as bereavement leave.
  Having always worked hard to be a model employee,
the claimant was greatly distressed by this turn of
events. Between the written warnings and the steady
increases in his workload—allegedly disproportionate
to those of other drivers—the claimant began to think
he was being set up by FedEx and, for the first time,
worried about losing his job.
   On September 15, 2009, the claimant began his work
day as usual. After taking inventory of the parcels, how-
ever, he concluded that his schedule would require fif-
teen delivery stops per hour, or one stop every four
minutes on average. After loading his vehicle, he
became convinced that this was too many stops and
that it would be impossible for him to complete all the
deliveries in the allotted time. When he reported his
stop count to the manager on duty, the claimant asked
if some of the stops could be assigned to another driver.
This request was refused.
   The day was ‘‘hot’’ and the claimant’s assigned truck
had a transparent roof to help illuminate the shelves
of parcels in the back. This type of roof tended to create
a greenhouse effect, increasing the temperature inside
the truck when the weather was warm. The vehicle was
not air-conditioned.
    The claimant proceeded that morning to his assigned
delivery area and began making his priority overnight
deliveries. He was rushing, but did manage to make all
of his deliveries in Mystic by the 10:30 a.m. deadline,
with the exception of one stop where the customer
was not present to sign for a package that required a
signature. The claimant then drove to the borough,
where he needed to complete his deliveries by noon.
At approximately 11:40 a.m., the claimant arrived at a
stop on Tipping Rock Road and concluded that the long
driveway to the house was too narrow and overgrown
to drive his truck down. With only twenty minutes left
to complete his morning deliveries, he opted not to
walk the parcel to the house. Instead, he attached the
parcel in the mailbox post and then left a voice message
on the customer’s phone. He just managed to finish his
remaining borough stops by noon. The claimant then
proceeded in the direction of Pawcatuck, making his
‘‘ ‘SOS deliveries,’ ’’ all of which needed to be completed
by 3 p.m. After that, he was scheduled to make his
‘‘ ‘E2’ ’’ deliveries, which needed to be completed by
4:30 p.m., at which time he was scheduled to make
some pickups before returning to Norwich.
  As the claimant was rushing to complete his ‘‘ ‘SOS
deliveries,’ ’’ he received a complaint from the Tipping
Rock Road customer. Given the written warnings he
had received in June, this complaint caused him signifi-
cant concern as he continued his route. Then, as the
claimant approached Pawcatuck, he received instruc-
tion to return to Mystic, on the opposite side of Stoning-
ton, to reattempt delivery of the parcel that was not
signed for that morning. The claimant requested that
the customer be asked to meet him at a midway point,
but his manager rejected this request, so the claimant
had to drive back to Mystic. When he returned to the
location, the customer again was not present to sign
for the package, and the claimant had to spend addi-
tional time filling out a detailed report before departing
again for Pawcatuck to resume his route.
  By this time, the claimant was significantly behind
schedule and under great stress. He had not had time
to stop for food or drink or to use the restroom, and
he was hot and sweating. To further complicate matters,
on his way back to Pawcatuck, he encountered traffic
delays, as the local high school was dismissing its stu-
dents. By then, he was one full hour behind schedule in
his deliveries and would need to complete an impossible
thirty stops per hour.
   As he rushed through his stops, running between
his truck and the customers’ houses carrying heavy
packages, the claimant began to feel ill and light-headed.
He noticed a fluttering sensation in his chest and a
shortness of breath, along with a growing sense of
panic. His pace started to slow as he felt increasingly
winded and more panicky. Fearing that he would be
written up again, the claimant pressed on for approxi-
mately one hour before concluding that he could not
finish his route. He stopped at the fire station on Liberty
Street in Pawcatuck, where he was scheduled to make
a delivery, and called FedEx for a substitute driver. He
took time to organize his remaining parcels for the
next driver, then went into the fire station, made his
scheduled delivery, and only then asked to be checked
out by fire personnel. His heart rate was found to be
more than 200 beats per minute, and an ambulance was
called. The claimant was rushed to Backus Hospital in
Norwich, where he came under the care of Amr Atef,
a cardiologist. An electrocardiogram showed that, at
one point, his heartbeat was 300 beats per minute.
   Emergency room testing showed that the claimant
presented with arrhythmia, an abnormal heart rhythm,
known as ‘‘ ‘atrial flutter.’ ’’ Atrial flutter is caused by
an electrical ‘‘ ‘short-circuit’ ’’ in the right atrium of the
heart, which serves as the heart’s natural pacemaker.
At some point while the claimant was in the emergency
room, his heart rhythm devolved into atrial fibrillation,
a form of irregular tachycardia, or irregular accelerated
heartbeat. Blood work taken at the hospital showed
that the claimant had low potassium levels, known as
hypokalemia, a potential result of dehydration.
  The claimant remained in the hospital overnight and,
with medication, his heartbeat eventually returned to
normal. The diagnosis on discharge the next afternoon
was ‘‘ ‘paroxysmal atrial flutter and fibrillation.’ ’’ The
claimant also was diagnosed with hypertension.
Although the arrhythmic episode had resolved, the
claimant was kept on beta-blocker medication, and was
advised to take aspirin and to monitor his potassium
intake. He was placed on medical leave until September
26, 2009, and instructed to follow up with a cardiologist,
who would have him wear a heart monitor to check
for repeats of the arrhythmia. When the claimant saw
Atef for a follow-up appointment on September 30, 2009,
the palpitations had stopped, his heart rhythms were
normal, and the claimant was feeling well. Although
Atef suspected that the September 15, 2009 incident
had been an isolated one, he instructed the claimant
to remain out of work until they received the heart
monitor results.
    On October 1, 2009, the claimant resumed his work-
outs at the gym, but he initially kept his workouts less
stressful than they had been before the incident. At
an appointment with Atef on November 6, 2009, the
claimant reported that he had returned to the gym
‘‘ ‘without any significant difficulty, but . . . contin-
ue[d] to have anxiety and stress.’ ’’ The claimant
reported having intermittent palpitations, particularly
around the time of the first informal hearing on his
workers’ compensation claim on October 30, 2009. Atef
opined that the claimant was doing well from a cardiac
standpoint but continued to be ‘‘ ‘very stressed out
about work.’ ’’ Because the cardiac event monitor the
claimant had been wearing showed that he was still
having episodes of paroxysmal atrial arrhythmia, Atef
increased the claimant’s dosage of beta-blocker medica-
tion and referred him to a cardiac electrophysiologist.
Atef advised the claimant to avoid dehydration, but
offered no specific instructions regarding his level of
activity. He did agree that the claimant should not return
to work until after his cardiac consultation and he also
recommended that the claimant see his primary care
physician to discuss medication for anxiety.
   Between late 2009 and early 2012, the claimant was
seen at varying times by seven health-care professionals
for symptoms or conditions related to the September
15, 2009 incident: Atef; Roger El-Hachem, the claimant’s
primary care physician; Steven L. Zweibel, the Director
of Cardiac Electrophysiology at Hartford Hospital;
Kevin J. Tally, a cardiologist who examined the claimant
for FedEx; Michele Chenevert, a licensed family thera-
pist and clinical social worker; Mahmoud Okasha, the
psychiatrist who supervised Chenevert; and Donald R.
Grayson, a psychiatrist who examined the claimant for
FedEx. These professionals each offered: (1) diagnoses
of the claimant’s physical and mental health conditions;
(2) accounts of the etiology of these conditions; (3)
medication and treatment recommendations; and (4)
opinions as to the claimant’s level of disability and
ability to resume work. This lengthy evaluation and
treatment history, which is detailed in the decision of
the commissioner, may be summarized as follows.
   With respect to the claimant’s physical condition, the
treating and evaluating physicians generally agreed that
the claimant suffered from atrial flutter, atrial fibrilla-
tion, and hypertension. In July, 2010, the results of a
second thirty day heart monitor test showed that he
continued to experience intermittent recurrence of
atrial flutter with rapid ventricular response. Although
El-Hachem initially opined that the claimant also had
hypertensive cardiomyopathy, defined by the commis-
sioner as damage to the heart muscle, he later con-
cluded—and Tally concurred—that the claimant did not
actually have cardiomyopathy.
   With respect to the claimant’s mental health condi-
tion, El-Hachem referred the claimant for a psychiatric
evaluation in May, 2010, after the claimant reported
that he had been experiencing anxiety and depression.
During his evaluation and subsequent therapy sessions,
the claimant reported feeling depressed, overwhelmed,
stressed, anxious, humiliated, embarrassed, and resent-
ful. He also reported difficulties with sleep and concen-
tration, and a tendency to avoid any objects or places
that he identified with FedEx. These symptoms were
magnified at times when the claimant had communica-
tions or interactions with FedEx, or around the anniver-
sary of the September 15, 2009 incident. At times, the
claimant associated his mental health symptoms with
the heart problems he experienced on that date. For
example, he reported that he was angry that had been
pressured to the extent that he was transported and
admitted to the hospital with atrial fibrillation and could
have died; that his mind raced with fears that his
arrhythmia would recur or that he would die; and that
he experienced flashbacks and ‘‘ ‘vivid dreams’ ’’ of the
2009 ambulance ride. At other times, he appeared to
associate his symptoms with resentment over how
FedEx had treated him as an employee, the perceived
unfairness of his situation, the stresses associated with
his ongoing legal battle with FedEx, and his reactions
to being out of work and to the associated financial
stresses.
  Chenevert diagnosed the claimant with adjustment
disorder with anxiety and depression, and rated his
level of functioning at 65 out of 100. Okasha diagnosed
him with post-traumatic stress disorder (PTSD) and
generalized anxiety disorder, which, the psychiatrist
opined, resulted in the claimant ‘‘ ‘being almost homeb-
ound’ ’’ and suffering from dysphoria, anxiety, weight
loss, insomnia, and an inability to relax or concentrate.
Grayson agreed that the claimant was not consciously
or unconsciously fabricating or amplifying his symp-
toms, and diagnosed him with PTSD, major depressive
disorder, panic disorder with agoraphobia, and hypo-
chondriasis.
   There was general agreement, then, as to the nature
of the claimant’s physical and psychological health
problems. With respect to the cause or etiology of these
conditions, there also was general agreement among
the medical experts that, although the claimant’s atrial
fibrillation and arrhythmia likely preexisted the events
of September 15, 2009, the physical stress, dehydration,
and psychological anxiety that he experienced on that
day could have aggravated the condition and caused it
to manifest. El-Hachem opined that ‘‘ ‘if a person has
an underlying atrial fibrillation, stress could increase
the heart rate enough to make the condition symptom-
atic.’ ’’ Zweibel likewise opined that ‘‘ ‘stress and anxi-
ety could be a contributing factor to these arrhythmias
[but] may not be the sole etiology.’ ’’ At one point,
Zweibel went so far as to state that ‘‘ ‘the physical stress
of [the claimant’s] job at FedEx was a significant con-
tributing factor in the development of his cardiac
arrhythmias.’ ’’ He later backed off this statement, how-
ever, and took the position that stress and anxiety can
bring on an arrhythmia. Even Tally, who examined the
claimant on behalf of FedEx, while opining that the
development of an atrial arrhythmia could be attributed
to his hypertension, also acknowledged that once the
claimant was in arrhythmia, the physical conditions and
stress under which he worked that day could have sped
up his heart rate and thereby ‘‘ ‘aggravated his uncon-
trolled atrial arrhythmias.’ ’’ Tally later more definitively
opined that one could presume, given the claimant’s
symptoms and history, that physical activity on Septem-
ber 15, 2009, aggravated the claimant’s underlying
arrhythmia, although he questioned whether the events
of that date changed the course of the illness in any
substantial way. The psychiatrists, Okasha and Gray-
son, both agreed with Tally that the claimant’s work at
FedEx aggravated his cardiac problems, and they fur-
ther opined that his work was the cause of or a signifi-
cant factor in the development of his PTSD. Okasha
explained that ‘‘ ‘[t]he consequences of being disabled
from his employment and the fear of future cardiac
episodes have resulted in symptoms that fulfill the crite-
ria for [PTSD. The claimant] experienced an event that
involved serious injury and a threat to his physical integ-
rity. His response involved intense fear, helplessness,
and horror. He suffers from recurrent and intrusive
distressing recollections and dreams of the event.’ ’’
   To treat his heart conditions, the claimant was, at
various times, prescribed metoprolol, lisinopril, Diovan,
and aspirin. His physicians also recommended that the
claimant undergo an ablation procedure, during which
surgeons would scar his heart to disrupt the atrial fibril-
lation, but the claimant declined to do so, and his meto-
prolol dose was increased instead. For his mental health
issues, the claimant was prescribed Lexapro and Klo-
nopin. He underwent weekly therapy sessions, as well
as monthly appointments for psychiatric medication
management. By the summer of 2012, however, Grayson
did not believe that these treatments had resulted in
maximum medical improvement and he recommended
that the claimant be treated by a PTSD specialist and
that alternative medications be considered.
  The only question on which there was a significant
divergence of opinions among the medical experts was
with respect to the claimant’s level of disability and
his ongoing inability to work. Following the events of
September 15, 2009, the claimant repeatedly sought and
obtained from his various treating physicians notes indi-
cating that he was not medically cleared to return to
work. There is some indication, however, that his physi-
cians at times were reluctant to continue issuing these
notes, or had doubts as to whether the claimant was
totally incapacitated.
  As previously noted, in September, 2009, Atef advised
the claimant to remain out of work until he received
the results of a heart monitor test. In early November,
Atef, after having reviewed the test results, agreed that
the claimant should not return to work until after he
had a cardiac consultation.
   On January 7, 2010, El-Hachem excused the claimant
from work for an additional month. On January 25,
2010, after having received a letter from the claimant
stating that his employer did not care about his well-
being and that he was not ‘‘ ‘emotionally, physically or
mentally ready’ ’’ to return to the work environment,
El-Hachem opined that the claimant was temporarily
totally disabled ‘‘ ‘due to atrial fibrillation and hyperten-
sive cardiomyopathy.’ ’’1 Because ‘‘ ‘aggravating fac-
tors’ ’’ such as anxiety and stress can worsen symptoms
of heart palpitations, El-Hachem indicated that ‘‘ ‘the
best thing to do is to have him rest or give him some
time to recover until we figure out what’s going on.’ ’’
  On April 15, 2010, during an examination by Tally,
the claimant reported working out on a treadmill at a
15.2 percent grade and a pace of 4.2 miles per hour for
thirty minutes, something Tally stated that most people
could not do for even three minutes. Tally opined the
claimant was only 10 percent to 11 percent disabled
and that he could return to work. ‘‘ ‘As a cardiologist,’ ’’
he wrote, ‘‘ ‘I would not disable him from work at this
time as it appears his [heart] rhythm is under adequate
control with current metoprolol; nor has he suffered
malignant hemodynamic effect such as syncope from
his arrhythmia.’ ’’
  On April 23, 2010, during a deposition, El-Hachem
was confronted with the claimant’s testimony about
these recent intense workouts. El-Hachem described
these sessions as a type of stress test that the claimant
obviously was passing. So long as the claimant did not
have fibrillation during these workouts, El-Hachem
stated, he would not consider him to be totally incapaci-
tated. Ultimately, El-Hachem conceded that he might
need to reconsider his earlier opinion to that effect.
Nevertheless, on May 26, 2010, El-Hachem gave the
claimant a note to permit additional medical leave from
work until June 26, 2010, in order to give him time to
use the cardiac event monitor.
  When the claimant returned to El-Hachem on June
26, 2010, El-Hachem did not issue a new disability note.
On July 8, 2010, however, Atef agreed to extend the
medical leave for another thirty days, because the claim-
ant was due to have a psychiatric evaluation. Atef issued
a note keeping the claimant out of work due to ‘‘recur-
rent cardiac arrhythmia, hypertension and persistent
anxiety.’’ Atef informed the claimant, however, that he
would not be able to give him any further extensions.
The claimant’s medically excused absence from work
thus expired on August 7, 2010.
  Lastly, the record reveals that the claimant has not
sought alternative employment since September 15,
2009. Approximately six months after the September
15, 2009 incident, the claimant approached FedEx seek-
ing to return to work on a part-time basis. FedEx
declined his request, taking the position that giving the
claimant part-time work would amount to a transfer,
and that company policy precluded employees from
requesting transfers within one year of having received
a written warning. Later in 2010, FedEx informed the
claimant that he would not have a job to return to when
he was able to work. In therapy, the claimant expressed
that he was hesitant to seek other employment, lest he
jeopardize his long-term disability and his case against
FedEx. To bolster his spirits, however, in the period
following his injury he did resume working out at the
gym, helped to paint his father’s house and to clear
snow from the roof, and kept busy helping neighbors.
He was granted Social Security disability benefits in
May, 2012.
  Following a formal hearing, the commissioner con-
cluded that the claimant had sustained physical and
psychological injuries arising out of and in the course of
his employment. Specifically, the commissioner found
that, prior to the date of injury, the claimant had a
subclinical heart condition of which he was unaware
and that did not require treatment or interfere with his
ability to engage in heavy physical labor. On September
15, 2009, FedEx subjected the claimant to unmanage-
able workload demands and forced him to work at an
unreasonably rapid pace, without allowing time to take
breaks for food, hydration, or even personal comfort.
As a result, the claimant became dehydrated, which
resulted in depressed potassium levels and left him
more susceptible to cardiac arrhythmia. In addition, the
commissioner found that these unreasonable demands
resulted in psychological stress, which, in tandem with
the physical exertion of rushing to keep up with his
schedule, elevated the claimant’s heart rate in excess
of 200 beats per minute and caused a supraventricular
tachycardiac event that required emergency transport
and hospitalization. As a result of the day’s events, the
claimant’s heart condition was aggravated significantly
and worsened to the point of requiring long-term, post-
hospital treatment, medication, and monitoring. The
commissioner also concluded that the physical trauma
that the claimant experienced on September 15, 2009,
and the ensuing emergency treatment were substantial
factors causing him to develop PTSD and related psy-
chological symptoms.
   With respect to the claimant’s ability to work, the
commissioner found that it was reasonable for the
claimant’s cardiologist and primary care physician to
exercise caution in monitoring his condition and
response to treatment before clearing him for work,
and, therefore, that he was temporarily totally incapaci-
tated for purposes of General Statutes § 31-307 (a)2 from
September 15, 2009 through August 7, 2010, the final
date to which Atef found the claimant to be disabled.
The commissioner found no credible evidence, how-
ever, that the claimant remained disabled after that
time, or that he was ready and willing to seek and
accept alternative employment. Consistent with these
findings, the commissioner determined that the claim-
ant was entitled to total incapacity benefits, pursuant
to § 31-307 (a), from September 15, 2009 until August
7, 2010, and he awarded benefits accordingly. The com-
missioner denied the claimant’s requests for partial or
total incapacity benefits for the period after August
7, 2010.
   The defendants filed a motion to correct several of
the commissioner’s findings. The commissioner denied
all of the requested corrections, other than to clarify
that the period of temporary total disability awarded
to the claimant amounted to forty-six weeks and four
days, rather than forty-six weeks and seven days as
originally stated. The defendants appealed from the
commissioner’s decision to the board, which affirmed
the findings and award. The defendants appealed from
the decision of the board to the Appellate Court, and
we transferred the appeal to this court pursuant to
General Statutes § 51-199 (c) and Practice Book § 65-
1. We now affirm.
                            I
   The defendants first argue that the board improperly
upheld the commissioner’s findings that the claimant
suffered compensable physical and psychological injur-
ies arising out of his employment. The resolution of
these claims depends in no small part on the standard
by which we must review the commissioner’s findings.
We therefore begin by setting forth the well established
standard of review applicable to workers’ compensa-
tion appeals.
   ‘‘The commissioner has the power and duty, as the
trier of fact, to determine the facts’’; (internal quotation
marks omitted) Gartrell v. Dept. of Correction, 259
Conn. 29, 36, 787 A.2d 541 (2002); and ‘‘[n]either the
. . . board nor this court has the power to retry facts.’’
(Internal quotation marks omitted.) Tracy v. Scherwit-
zky Gutter Co., 279 Conn. 265, 272, 901 A.2d 1176 (2006);
see also Regs., Conn. State Agencies § 31-301-8. ‘‘The
conclusions drawn by [the commissioner] from the
facts found [also] must stand unless they result from
an incorrect application of the law to the subordinate
facts or from an inference illegally or unreasonably
drawn from them. . . . [Moreover, it] is well estab-
lished that [a]lthough not dispositive, we accord great
weight to the construction given to the workers’ com-
pensation statutes by the commissioner and review
board. . . . Cases that present pure questions of law,
however, invoke a broader standard of review than is
ordinarily involved in deciding whether, in light of the
evidence, the agency has acted unreasonably, arbi-
trarily, illegally or in abuse of its discretion. . . . We
have determined, therefore, that the traditional defer-
ence accorded to an agency’s interpretation of a statu-
tory term is unwarranted when the construction of a
statute . . . has not previously been subjected to judi-
cial scrutiny [or to] . . . a governmental agency’s time-
tested interpretation . . . .
   ‘‘Furthermore, [i]t is well established that, in resolv-
ing issues of statutory construction under the act, we
are mindful that the act indisputably is a remedial stat-
ute that should be construed generously to accomplish
its purpose. . . . The humanitarian and remedial pur-
poses of the act counsel against an overly narrow con-
struction that unduly limits eligibility for workers’
compensation. . . . Accordingly, [i]n construing work-
ers’ compensation law, we must resolve statutory ambi-
guities or lacunae in a manner that will further the
remedial purpose of the act. . . . [T]he purposes of
the act itself are best served by allowing the remedial
legislation a reasonable sphere of operation considering
those purposes.’’ (Citations omitted; internal quotation
marks omitted.) Sullins v. United Parcel Service, Inc.,
315 Conn. 543, 550–51, 108 A.3d 1110 (2015). With these
principles in mind, we turn to the defendant’s claims
on appeal.
                               A
   The defendants first argue that the commissioner’s
finding that the claimant’s heart condition arose out of
his employment on September 15, 2009, is unsupported
by the record. Specifically, the defendants contend that
(1) it is ‘‘counterintuitive’’ to think that a ‘‘physical speci-
men’’ such as the claimant could have been ‘‘even
phased’’ by having to run back and forth from his truck
in the heat carrying heavy packages, and (2) ‘‘the sheer
reality is that most employers ask a great deal of their
workers,’’ and the stresses associated with the claim-
ant’s work at FedEx were nothing out of the ordinary.
On the basis of these assumptions, the defendants posit
that the physical and psychological stresses associated
with the claimant’s employment on the date in question
could not have triggered his episodes of cardiac arrhyth-
mia and tachycardia and the onset of hypertension. We
are not persuaded.
   We begin by noting that, to be compensable under
the act, a personal injury sustained by an employee
must arise both (1) out of and (2) in the course of his
employment. General Statutes § 31-284 (a). ‘‘Speaking
generally, an injury arises out of an employment when
it occurs in the course of the employment and as a
proximate cause of it.’’ (Internal quotation marks omit-
ted.) Blakeslee v. Platt Bros. & Co., 279 Conn. 239,
244–45, 902 A.2d 620 (2006). It is well established that,
when an employee has a preexisting, asymptomatic
medical condition, and that condition is aggravated by
injuries sustained during the course of his employment
and thereafter becomes symptomatic and necessitates
treatment, the injury is deemed to have arisen out of the
employment and is compensable. As we have explained:
‘‘[There is] no difference between a fresh infection and
the awakening of an old one. The [workers’ compensa-
tion] statute is not concerned with pathology, but with
industry disability; and a disease is no disease until it
manifests itself. Few adults are not diseased, if by that
one means only that the seeds of future troubles are
not already planted; and it is a [commonplace] that
health is a constant warfare between the body and its
enemies; and infection mastered, though latent, is no
longer a disease, industrially speaking, until the individ-
ual’s resistance is again so far lowered that he suc-
cumbs.’’ (Internal quotation marks omitted.) Smith v.
State, 138 Conn. 620, 624–25, 88 A.2d 117 (1952), quoting
Judge Learned Hand in Grain Handling Co. v. Sweeney,
102 F.2d 464, 466 (2d Cir.), cert. denied, 308 U.S. 570,
60 S. Ct. 83, 84 L. Ed. 478 (1939); see also Deschenes
v. Transco, Inc., 288 Conn. 303, 322, 953 A.2d 13 (2008)
(noting that employer must take employee in state of
health in which it finds him). Our sister courts routinely
have applied this rule in the context of work-related
episodes of cardiac arrhythmia or tachycardia.3
   In the present case, the defendants argue that the
commissioner was required to reject the opinions of
five medical experts, all of whom, with knowledge of the
claimant’s exemplary physical condition and impressive
exercise regimen, opined that his conditions of employ-
ment did aggravate or could have aggravated his heart
problems. Most notably, the defendants’ own cardiology
expert testified that ‘‘one could presume, given the
claimant’s symptoms and history, that physical activity
on September 15, 2009, aggravated [his] underlying
rhythm.’’ ‘‘[T]he trier of fact—the commissioner—was
free to determine the weight to be afforded to that
evidence.’’ Marandino v. Prometheus Pharmacy, 294
Conn. 564, 594, 986 A.2d 1023 (2010). After reviewing
all of the relevant evidence of record, the commissioner
rejected the defendants’ theory, and we will not disturb
that finding on appeal.
   In this regard, we cannot help but observe that, in
their briefs to this court, the defendants studiously have
avoided any mention of certain noteworthy facts, facts
that were found by the commissioner and that are sup-
ported by adequate evidence in the record. In arguing
that the claimant’s employment could not have been a
proximate cause of his physical injuries, for example,
the defendants neglect to discuss the following facts:
that the claimant was required to spend a ten to twelve
hour day working in an unair-conditioned truck that
magnified the ambient heat; that although this ‘‘dedi-
cated, hardworking’’ employee had repeatedly informed
his managers at FedEx that his delivery schedule had
become unworkable, they continued to increase his
stop count; that this delivery schedule not only left no
time for the claimant to take his allotted lunch break
from the time he began work at 7 a.m. or 8:30 a.m. until
after 4:30 p.m., but that there was not even time for
him to stop for hydration or to use the restroom during
that period; and that, as a result of these factors, he
became dehydrated and potassium depleted on the date
in question, leaving him especially vulnerable to certain
forms of cardiac arrhythmia. We are skeptical of the
defendants’ suggestion that most Connecticut employ-
ers require similarly situated employees to labor under
such conditions.
   Nor have the defendants offered any authority for
their ‘‘intuitive’’ belief that an individual who is capable
of exercising intensely necessarily is immune from the
types of work-related physical and psychological
stresses that might aggravate a latent heart condition.
Rather, the defendants’ intuitions were contradicted by
the preponderance of expert medical evidence in the
record, which the commissioner credited. We are com-
pelled to defer to those findings. See Fair v. People’s
Savings Bank, 207 Conn. 535, 539–40, 542 A.2d 1118
(1988).
                             B
   We next consider the defendants’ argument that the
claimant’s PTSD and other psychological injuries are
not compensable under the act. The defendants contend
that, as a matter of law, compensation for those injuries
was barred by General Statutes § 31-275 (16) (B) (iii).
That statute provides that, for purposes of the act, a
compensable personal injury ‘‘shall not be construed
to include . . . [a] mental or emotional impairment
that results from a personnel action, including, but not
limited to, a transfer, promotion, demotion or termina-
tion . . . .’’ General Statutes § 31-275 (16) (B) (iii). The
defendants argue that the events that the commissioner
identified as causes of the claimant’s PTSD and other
psychological injuries—the arrhythmia and tachycardia
he experienced on September 15, 2009, and the ensuing
ambulance ride and hospitalization—actually arose
from and were merely components of (1) the claimant’s
preexisting anxieties over having received two repri-
mands in June, 2009, which gave rise to a fear that
he would lose his job if he were to receive another
reprimand, and (2) the stresses he suffered after the
events of September 15, 2009, as a result of being out of
work and prosecuting a contested compensation claim.
Accordingly, the defendants contend, the claimant’s
psychological injuries resulted from a personnel action
and are not compensable. We are not persuaded.
   We recognize that there is evidence in the record to
support the defendants’ theory that, both prior to and
on the claimed date of injury, the claimant experienced
worry and anxiety with respect to his employment situa-
tion with FedEx. There also is evidence that such feel-
ings persisted in the months following the injury, during
which time the claimant was unable to resume his
employment with FedEx and the parties engaged in
a contentious legal dispute. The commissioner found,
however, that other factors arising from the claimant’s
employment, factors that were unrelated to any actual
or potential4 personnel actions, also were substantial
factors in causing his PTSD and associated anxiety,
panic, and depression. See Marandino v. Prometheus
Pharmacy, supra, 294 Conn. 591 (for purposes of work-
ers’ compensation, claimant need only establish that
employment was substantial factor causing claimed
injury). Specifically, the commissioner found that the
claimant’s PTSD resulted from the September 15, 2009
attack of atrial fibrillation and resulting need for emer-
gency medical treatment, which led the claimant to fear
that he would die of a heart attack and to feel unsafe
when traveling far from his treating physicians.
Although the commissioner agreed that the loss of the
claimant’s job likely aggravated his psychological condi-
tion, the commissioner expressly rejected the defen-
dants’ theory that personnel considerations were the
primary cause of his anxiety and effectively eclipsed
all other contributing factors. Rather, the commissioner
credited the opinions of the psychiatric experts that
‘‘the emotional trauma of having a cardiac malfunction,
requiring emergency transport with advanced life sup-
port to a hospital—where he then required prolonged
emergency measures to restore his heart to a sustain-
able heartbeat—represents a life-threatening event that
was sufficient to cause PTSD.’’
  The commissioner further found that the September
15, 2009 attacks of arrhythmia and tachycardia that
precipitated the claimant’s PTSD arose not only from
employment-related anxieties but also, to a substantial
extent, from (1) physical and mental exhaustion
resulting from having to race to meet an unreasonable
and unmanageable delivery schedule on a hot day in
heavy traffic, and (2) dehydration and mineral depletion
resulting from having to work long hours in a hot truck
without adequate opportunity to eat, drink, or use a
restroom. There is sufficient evidence in the record to
support the commissioner’s findings in this regard; see
part I A of this opinion; and the defendants have failed
to provide any plausible explanation as to how the
dehydration and resultant mineral deficiencies that pre-
cipitated the claimant’s heart problems and associated
PTSD could have been the result of personnel decisions,
real or imagined. We are compelled again to defer to
the commissioner’s factual findings. Accordingly, we
conclude that the board properly upheld the commis-
sioner’s determination that the claimant’s psychological
as well as physical injuries were compensable under
the act.
                           II
   The defendants next argue that, even if the claimant’s
injuries arose out of his employment and were compen-
sable, the commissioner went astray in concluding that
those injuries entitled him to total incapacity benefits
for the entire period from September 15, 2009 through
August 7, 2010. We have defined total incapacity as ‘‘the
inability of the employee, because of his injuries, to
work at his customary calling or at any other occupation
which he might reasonably follow.’’ (Internal quotation
marks omitted.) Rayhall v. Akim Co., 263 Conn. 328,
350, 819 A.2d 803 (2003). The defendants offer two
arguments as to why the claimant was capable of resum-
ing work of some sort prior to August 7, 2010.5 First,
they contend that the claimant could not have been
totally disabled for that entire period if he was able to
return to the gym a mere two weeks after the incident
and to resume his normal vigorous workouts by the
spring of 2010. Second, the defendants argue that the
opinions of the treating physicians who excused the
claimant from work during the nearly forty-seven weeks
in question are, for a variety of reasons, not credible,
and that the commissioner instead should have credited
the opinion of the defendants’ expert, who only would
have excused the claimant from work for less than that
time period. We disagree.
  Once again, the defendants’ arguments challenge the
commissioner’s factual findings and credibility determi-
nations and, therefore, must overcome a heavy burden.
See R. Carter et al., 19 Connecticut Practice Series:
Workers’ Compensation Law (Supp. 2015–2016) § 8:37,
p. 163 (‘‘the determination of whether a claimant is
totally incapacitated is a factual one, and particularly
impervious to appellate review’’ [internal quotation
marks omitted]). With respect to the defendants’ first
argument, the commissioner found that the claimant
was able to resume his gym workouts over time without
difficulty but also found that the claimant remained
‘‘very stressed out about work’’ and continued to suffer
related bouts of paroxysmal atrial arrhythmia. The com-
missioner concluded that, even if the claimant had no
physical restrictions on account of his heart condition,
it was reasonable for his treating physicians to hold
him out of work during the period in question to observe
and monitor his condition and his response to treat-
ment. During that time period, the claimant saw various
physical and mental health professionals for diagnostic
and treatment purposes, underwent several periods of
prolonged heart monitoring, weighed whether to
undergo surgical treatment, and experimented with var-
ious medications to treat his heart conditions and anxi-
ety. Indeed, at the time the claimant met with the
defendants’ psychiatric expert, Grayson, in August,
2010, Grayson recommended that the claimant continue
to experiment with alternative medications and treat-
ment modalities so as to better control his mental health
conditions. In light of the commissioner’s well substan-
tiated finding that the claimant, despite his impressive
physical condition and fitness regimen, nevertheless
had suffered work-related heart injuries and associated
PTSD on September 15, 2009; see part I A of this opinion;
we cannot gainsay the commissioner’s ultimate conclu-
sion that it was a reasonable precaution for the claim-
ant’s treating physicians to keep him fully out of work
until they were able to complete their diagnoses and
settle on a treatment regimen that would protect him
from both the physical and psychological stresses of
work.
   The defendants’ second argument—that the various
physicians who recommended that the claimant remain
completely out of work after November 18, 2009, were
not credible, and that the commissioner instead should
have credited the opinions of the defendants’ expert,
who concluded that he was only partially incapaci-
tated—likewise founders against our standard of
review. See Marandino v. Prometheus Pharmacy,
supra, 294 Conn. 594 (‘‘[t]he credibility of the witnesses
and the weight to be accorded to their testimony is for
the trier of fact’’ [internal quotation marks omitted]);
Nicotra v. Bigelow, Sanford Carpet Co., 122 Conn. 353,
359, 189 A. 603 (1937) (‘‘[a] conclusion reached by a
commissioner by comparison and examination of con-
flicting professional opinion . . . can rarely be found
erroneous’’). In the present case, the commissioner
found the opinion of the defendants’ expert, Tally, to
be less persuasive than that of the claimant’s treating
physicians, and nothing in our review of the record
compels us to disturb that finding. Accordingly, we
reject the defendants’ argument that the board improp-
erly upheld the commissioner’s finding that the claimant
was temporarily totally incapacitated until August 7,
2010.6
  The decision of the Workers’ Compensation Review
Board is affirmed.
      In this opinion the other justices concurred.
  1
     As we previously have noted, El-Hachem later concluded that there was
insufficient evidence to support a diagnosis of cardiomyopathy.
   2
     General Statutes § 31-307 (a) provides in relevant part: ‘‘If any injury for
which compensation is provided under the provisions of this chapter results
in total incapacity to work, the injured employee shall be paid a weekly
compensation equal to seventy-five per cent of the injured employee’s aver-
age weekly earnings as of the date of the injury . . . .’’
   3
     See, e.g., Crescent Towing & Salvage Co. v. Collins, 228 Fed. Appx. 447,
448–49 (5th Cir. 2007); Dept. of Correction v. Industrial Commission, 182
Ariz. 183, 187, 894 P.2d 726 (App. 1995); Oxley v. Sattler, 710 So. 2d 261,
265 (La. App. 1998), writ denied as improvidently granted, 739 So. 2d 183
(La. 1999); Carson Tahoe Regional Healthcare v. Jain, Docket No. 54725,
2010 WL 5135239 (Nev. December 9, 2010); Sullivan v. Sysco Corp., 199
App. Div. 2d 849, 849–50, 606 N.Y.S.2d 77 (1993); Morley v. State Accident
Ins. Fund, 23 Or. App. 82, 84–86, 541 P.2d 160 (1975); see also Sullins v.
United Parcel Service, Inc., supra, 315 Conn. 551–52 (stating principle with
respect to heart disease generally); J. Asselin, Connecticut Workers’ Com-
pensation Practice Manual (1985) p. 54 (advising that, in determining
whether heart disease arises out of employment, commissioner should con-
sider whether, in period leading up to attack, claimant worked under extreme
temperatures or performed activities requiring unusual exertion or emo-
tional stress).
   4
     Even if we were to accept the defendants’ theory of the etiology of the
claimant’s psychological injuries, the defendants conceded at oral argument
before this court that their theory depends on the assumption that the
claimant suffered significant stress and anxiety on September 15, 2009, out
of a fear that he would be reprimanded or fired if he were unable to satisfy
FedEx’s performance expectations. The defendants, however, were unable
to identify anything in the text or history of § 31-275 (16) (B) (iii) suggesting
that that provision applies to mental or emotional impairments arising from
a potential or hypothetical employment action, or one that an employee
fears might occur. Because we must defer to the commissioner’s finding
that the claimant’s PTSD did not arise primarily from such fears, however,
we need not determine whether such fears, taken alone, could implicate the
statutory exception in the absence of any actual adverse personnel action.
   5
     See footnote 6 of this opinion.
   6
     To the extent that the defendants also argue that, as a matter of law, a
physician’s note that keeps a patient out of work for precautionary reasons
cannot constitute evidence that the patient is totally incapacitated unless
the note expressly opines that the patient is incapable of working in any
capacity, we decline to review this claim because it is inadequately briefed.
See Stafford v. Roadway, 312 Conn. 184, 188 n.4, 93 A.3d 1058 (2014). We
do note, however, that the board, when construing § 31-307 (a), has afforded
wide latitude to commissioners with respect to the types of evidence they
may consider in evaluating whether a claimant is totally disabled. See O’Con-
nor v. Med-Center Home Health Care, Inc., 140 Conn. App. 542, 554, 59
A.3d 385, cert. denied, 308 Conn. 942, 66 A.3d 884 (2013). The board has
refrained from requiring any specific type of evidence, and has permitted
the fact finder to extrapolate unemployability from various sources. Id.,
554–55. In particular, the board has affirmed an award of total incapacity
benefits even in the absence of medical evidence categorically stating that
a claimant was totally unable to work. Id., 555. The board’s interpretation
of the statute is consistent with the remedial purposes of the act, and also
with the approach followed by other jurisdictions, which have concluded
that a workers’ compensation commissioner may find an employee totally
disabled on the basis of a note from a physician that recommends that the
employee remain out of work for a specified period of time but does not
expressly opine that the employee is totally disabled or unable to work in
any capacity. See, e.g., Marriott at Wardman Park v. Dept. of Employment
Services, 85 A.3d 1272, 1277 (D.C. 2014); Blair v. Wal-Mart Stores, Inc., 818
So. 2d 1042, 1051 (La. App. 2002); Corbin v. Moody’s Restaurant, Me. Work-
ers’ Compensation Board No. 05-019096 (May 15, 2006).
