fatigue_handbook_a5

Stressforskningsinstitutet
Fatiguea self health guide

2
This guide is part of the fatigue risk
management training of project
MARTHA. It serves to provide parti-
cipating seafarers with a concise yet
sound overview of what fatigue is. The
main focus is threefold:
1. What are the causes of fatigue?
2. What are the consequences of
fatigue?
3. How can fatigue be prevented?
With this fatigue self-help manual we
hope to eventually contribute to safer
seafaring.
This project is sponsored by the TK
foundation
Project MARTHA, represented by:
• Stress Research Institute,
Stockholm, Sweden;
• Southampton Solent University,
Southampton, United Kingdom;
• Southampton Marine and
Maritime Institute, Southampton,
United Kingdom;
• Centre of Maritime Health and
Society, Esbjerg, Denmark;
• Dalian Maritime University,
Dalian, China;
• InterManager, Cyprus
Preface

3
1 Basics of sleep
We spend on average one third of our
time alive in a state called sleep. It is
equally vital for our survival as food
and water. Without a sufficient amount
of sleep we will not only become more
vulnerable to illnesses and diseases, but
also our alertness and performance are
strongly related to the sufficiency of
our sleep. This chapter provides a basic
overview of the phenomenon sleep.
Sleep stages and cycles
Sleep is not a passive state where
nothing happens in our brain. On the
contrary. Our brain is highly active
during sleep and sleep can be divided
in several distinct stages. Upon falling
asleep we usually enter stage 1, the
lightest of all sleep stages from which
it is easy to wake up. Very brief periods
of stage 1 sleep that are followed by
waking up again are referred to as mi-
cro-sleeps. Most of the time, you will
not remember your own mirco-sleeps.
If not woken up, you will after about
5 to 10 minutes enter stage 2 sleep.
About half of all our sleep consists of
stage 2 sleep. As sleep continues you
will enter deep sleep, consisting of sta-
ge 3 and 4. Waking up from deep sleep
is hard and if you succeed you will
initially feel groggy and disoriented
and have difficulties to perform, a phe-
nomenon called sleep inertia. This can
last for 15 minutes or more. Finally, a
stage called REM sleep might occur at
the end of a sleep cycle, during

4
which most of our dreaming takes pla-
ce. Thus, a sleep cycle looks as shown
in Figure 1. During a normal night of
sleep we go through about 4 to 5 of
these cycles each being about 90 to 120
minutes in length.
Figure 1. A typical night of sleep. Sleep stages are shown on the vertical axis plotted
against clock time (adapted from Principles and Practice of Sleep Medicine, 5th Edition,
Elsevier, 2011)
Figure 2. Obtained amount of sleep decreases with aging, especially the deep sleep stages
3 and 4, collectively referred to as slow wave sleep (SWS). Also REM sleep decreases whe-
reas time awake after having fallen asleep (WASO) increases (adapted from Principles and
Practice of Sleep Medicine, 5th Edition, Elsevier, 2011)
How much sleep?
The amount of sleep we need differs
between individuals. Most adults,
however, need somewhere between
7 and 9 hours per day. With aging,
the total amount of sleep we obtain
reduces as well as the amount of the
different sleep stages (see Figure 2)
Wake
S1
S2
S3
S4
REM
Body
movement
24 1 2 3 4 5 6 7
855 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
600
0
100
200
300
400
500
Age
Sleep latency
WASO
REM
SWS
Stage 2
Stage 1

5
Sleep disorders
Sleeping poorly might in some cases
indicate a sleep disorder. In that case,
a physician rather than just good sleep
habits is needed. The five most com-
mon sleep disorders are briefly descri-
bed here.
Insomnia includes the inability to fall
asleep and/or to stay asleep as long as
desired. It is the most common sleep
disorder among people working irregu-
lar shifts.
Sleep apnea/hypopnea is most com-
mon in overweight men over 40 who
snore. It includes either a stop (ap-
nea) or reduction (hypopnea) in his/
her breathing during sleep. Due to the
immediate shortness of oxygen in the
blood, the sleeper will suddenly wake
up, gasping to take a breath and fall
back asleep immediately afterwards.
It can happen several hundred times a
night without the sleeper being aware
of it. What it will eventually result in is
excessive sleepiness and fatigue during
the day. Successful treatments are
available.
Narcolepsy includes uncontrollable
attacks of sleep during the day. The
sleep episodes typically last a few mi-
nutes and reoccur after several hours.
Although it is not that common, the
symptoms are very problematic for
sufferers. It is a lifetime condition with
unknown causes.
Restless legs syndrome and periodic
limb movements during sleep is a
neurological condition. It is usually
experienced as tingling or prickling
sensations in the limbs (most often the
legs) that makes the sufferer to want to
get up and move around. The sympt-
oms usually peak at bedtime, making
it hard to fall asleep and are even
associated with repeated limb jerking
during sleep. Symptoms can be treated
with medication.
Delayed or advanced sleep-phase
syndrome occur when your biological
clock is out of synch with the environ-
ment. Having difficulties going to sleep
at night may be indicative of delayed
sleep-phase syndrome and is seen most
often in adolescents and young adults.
Advanced sleep-phase syndrome is
mostly seen in older people, having
troubles staying awake in he evening
and waking up too early in the mor-
ning. Bright light may help both groups
of people to keep their biological clock
in synch with the environment.
Sleep quality versus quantity
It is not just the amount of sleep that
counts, but also the quality. Not all
sleep is of the same quality and not all
sleep will give you the same recuperati-
ve benefits. Sleep of the highest quality
is obtained at night, whereas sleeping
at other times of the day will be more
disrupted, shorter, and thus of lower
quality. Another aspect important for
good recuperation is a certain amount
of uninterrupted sleep, about six hours
of uninterrupted sleep for a person that
usually sleeps eight hours. Sleep quality
and quantity can simply be improved
by taking actions such as:

6
• calm down before going to bed
• improve the sleep environment by
making it quiet, dark, and cool
• avoid alcohol and caffeine prior to
sleep (no caffeine for at least six
hours before bedtime)
• try to spend as much of the day in
daylight
• be active (both physically and
mentally) during the day, but not
too close to bedtime
• follow your own rhythm, so sleep
and wake early when you are a
morning person and sleep and
wake late when you are an evening
person
Points to remember
• Your body needs sleep. You can
not eliminate that need.
• Most people need between 7 to
9 hours of sleep per night.
• The amount of sleep obtained
decreases with aging.
• Sleep quality is equally impor-
tant as sleep quantity.

7
2 The biological clock
Our body is programmed to sleep at
night and stay awake during the day.
However, many more processes in our
body are regulated in a similar way,
that is with a rhythm that is completed
in a about a day. These are therefore
called ciracadian rhythms (from the
Latin circa, meaning around, and dies,
meaning day). This chapter describes
those rhythms, their importance, and
their connections to sleep and fatigue.
Biological rhythms
All biological rhythms in our body are
synchronized with each other and with
the environment, in order for the body
to work as efficiently as possible (see
Figures 3 and 4). The biological clock
controls and synchronizes the timing
of all biological processes, such as
heart rate and digestion. When chan-
ging your sleep and wake time, this
synchronization will be disrupted.

8
Time cues
How does our body know what time it
is? The most important time cue comes
from the environment and is light
(see the image on the title page of this
chapter). Light is directly affecting the
central biological clock in the brain,
for instance by acutely terminating the
synthesis of melatonin (Figure 3). Light
can therefore also be used to slightly
shift your rhythm back or forth. Early
morning light exposure will shift your
rhythm towards morningness, whereas
evening light exposure will shift it
towards eveningness. Even in circum-
stances without any environmen-
tal cues, the body will continue its
rhythms, indicating that the body has
an internal clock.
Melatonin
Cortisol
Error on a
performance
task
High
Low
37,5˚ C
36˚ C
Body
temperature
Growth
hormone
Day 1 Day 2 Day 1
Figure 3. Some examples of biological rhythms (from Shifting to Wellness, Keyano College, 1995)

9
Figure 4: Sleep and performance related parameters peak at specific times of day as well as
many other bodily functions.
Sleepiness and alertness
Sleepiness and alertness are under
the control of our biological clock.
Sleepiness is most severely experienced
between 2 AM and 6 AM, whereas
alertness usually peaks around 10 AM
and later on between 6 PM and 8 PM.
However, it is not only the biological
clock that plays a role here, but also
your sleep, that is, the time you have
been awake. With time awake alertness
gradually decreases, whereas during
sleep it rapidly recovers again. These
two processes (the biological clock and
time awake) together indicate your
level of alertness. A slight increase in
sleepiness may occur in the afternoon.
Although this is often referred to as
being a post-lunch dip, it even occurs
without having eaten any lunch at all.
Although many environmental cues are
often mentioned as increasing alert-
ness, the only one that really does so is
light.
Sleep
Irregular sleep times will result in con-
flicts with your biological clock, where
you will attempt to sleep at times when
the body is less willing to do so. This
will result in a shorter sleep and even
alter the structure of sleep, making it
less restorative. Figure 5 illustrates the
sleep duration that you are likely to
obtain as a function of bedtime. Note
that eight hours of sleep is most easily
reached with a bedtime between 22
PM and midnight. It also shows that
an attempt to sleep after a 6 to 12 AM
watch is likely to give you a maximum
of only 3 hours of sleep.
Light-dark cycle
Noon
Midnight
0200
Deepest sleep
1200
0000
18000600
0430
Lowest body
temperature
0645
Sharpest rise in
blood pressure
0730
Melatonin secretion stops
0830
Bowel movement likely
0900
Highest testosterone secretion
1000
High alertness
1430
Best coordination
1530
Fastest reaction time
1700
Greatest cardiovascular eﬃciency
and muscle strength
1830
Highest blood pressure
1900
Highest body temperature
2100
Melatonin secretion starts
2230
Bowel movements suppressed

10
240200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200
9
0
1
2
3
4
5
6
7
8
Time of day
Sleep(hours)
Points to remember
• Two natural sleep periods exist: at night
(23:00-06:00) and during the afternoon
(14:00-16:00).
• Alertness peaks in the morning (9:00-
11:00) and early evening (18:00-20:00).
• Light and darkness are the strongest cues
to your biological clock.
• Working and sleeping irregularly will
disturb your biological rhythms.
Figure 5: Sleep duration (vertical axis) as a function of time of day at which you attempt to
sleep.

11
3 Effects of irregular work
Irregular work means that the dura-
tion and timing of your work periods
are highly variable. This will result
in conflicts between work and your
biological clock. Although these con-
flicts can vary in magnitude, its effects
will always be negative. This chapter
describes those effects, from fatigue to
adverse health, and how severe they
can ultimately become.
Fatigue
Although the terms fatigue and sleepi-
ness are often used as synonyms, they
are quite different. The end-point of
sleepiness is always sleep, whereas
fatigue does not always end in sleep.
Moreover, fatigue has physical aspects
involved as well. Therefore, a good
definition of fatigue could be a pro-
gressive loss of mental and physical
alertness that can end in sleep. Physical
fatigue can occur after prolonged pe-
riods of physical activity. You will feel
weaker and have reduced endurance.
You may also feel that your muscles
become cramped and/or stiff. Mental
fatigue, on the other hand, is mainly
a consequence of lack of sleep, sleep
at different times, mental stress, or a
high workload. With increasing fatigue
several cognitive abilities may start to
wane. This is, for instance, illustrated
in Figure 6.

12
Other aspects that will deteriorate
are your memory, decision making,
and the way you are able to deal with
new situations. This means that you
will have to work harder in order to
avoid errors. Eventually, you may even
experience sleep for short periods (a
few seconds) without you realizing it
(so called micro-sleeps). During those
micro-sleeps you have no control at all
over the task you are performing.
Causes of fatigue
Factors that influence seafarer fatigue
can be divided into three categories:
Figure 6. Performace on a grammatical reasoning task as a function of time awake (adap-
ted from Lemond and Dawson, 1999)
293 5 7 9 11 13 15 17 19 21 23 25 27
10
−30
−25
−20
−15
−10
−5
0
5
Amount of time awake (Hours)
Meanrelativeproblems
Acceptable performance
Dangerously poor performance
1. Work factors 2. Environmental factors 3. Personal factors
• Irregular schedules
• Weather & tempera-
ture
• Biological rythms
• Long periods of work
• Ship condition and
equipment
• Quality and quantity
of sleep
• On-call nature of work • Lightning
• Physical fitness and
health
• Crew proficiency • Noise levels • Age
• Workload • Time of day • Family obligations

13
Signs of fatigue
The danger of fatigue lies in the fact
that the fatigued individual often does
not realize how tired and impaired he
or she is. The following list of signs
may be of help. If you experience one
major indicator or a few of the other
indicators, aim to get more sleep. Also
check the people you are working with
if they show any of the indicators and
inform them if appropriate.
Impact of irregular work on
sleep and performance
Lack of sleep or a reduction in the qua-
lity of sleep is the main factor affecting
your fatigue, health, and performance.
Sleep can be lost by reducing a single
sleep period to a large extent (acute
sleep loss) or by gradually building
up a sleep debt over time by reducing
consecutive sleep episodes (accumula-
ted sleep loss). On call work can also
affect your sleep quality, due to the
stress of being on standby, and because
sleep may be interrupted by calls from
work. The only way to correct sleep is
with adequate recovery sleep.
Performance is most importantly affec-
ted by time of day, being significantly
lower during the night, and slightly
lower in the afternoon. Working at
night is therefore always a risk. This
effect is very clearly seen when looking
at vehicle accidents on the road (Figure
7). Although much fewer vehicles are
on the road at night, the number of
accidents peaks at night.
Major indicators of fatigue Other indicators of fatigue
Eyes go out of focus or close for a moment Heavy and burning eyes
Slowed, slurred speech Headaches and stomach ache
Blurred vision Drowsiness
Wandering and disconnected thoughts
Inattention to minor but potentially impor-
tant details
Constant yawning Reduced motivation
Head nodding Degraded mental abilities
Forgetting to communicate with crew Increased distractibility and irritability
Incorrect reading of equipment
Reluctance to initiate tasks and take
command
Forgetting to check ship position on a
regular basis
Reduced sense of humor
Missing a reference point Tendency to exaggerate
Not remembering the last command given Tendency to take unnecessary risks
Missing radio calls Degraded sense of balance
Giving wrong commands

14
Another illustration of reduced perfor-
mance at night is the fact that many
well-known disasters at sea have taken
place during the night hours, when
those responsible were suffering from
sleep loss. Those include the Exxon
Valdez grounding, the grounding of the
bulk carrier Raven Arrow, the ramming
of the tanker Hamilton Energy by the
bulk carrier Nirja, and the grounding
of the Shen Neng 1.
Health consequences
It is not only your sleep and perfor-
mance that suffer. Working irregularly
will also adversely affect your health.
Among the health problems that those
working irregularly are more likely to
suffer from are gastrointestinal distur-
bances (e.g. heartburn, peptic ulcer,
diabetes), cardiovascular disorders
(e.g., hypertension, high cholesterol),
sleep disorders (e.g., insomnia), and
substance abuse (e.g., caffeine, nicotine,
alcohol).
240200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200
700
0
100
200
300
400
500
600
Time of day
Numberofvehicleaccidents
Figure 7. A strong increase of fatigue related vehicle accident occurs at night.
Points to remember
• Irregular work disrupts your bio-
logical rhythms.
• Irregular work increases fatigue.
• Irregular work affects your mood
and health.
• Irregular work degrades your
performance.

15
4 Coping with fatigue
An enormous amount of strategies to
deal with fatigue have over the past
decades been mentioned in the popu-
lar media. The question that remains,
however, is: do they all work? This
chapter will discuss the strategies that
you can use and the strategies that you
should not use in order to cope with
fatigue.
Sleep
As mentioned already in chapter 1,
sleep is by far the mot effective strategy
to overcome fatigue. In order to maxi-
mize the restorative value of your sleep
it is good to take the following aspects
into account.
Your sleep environment can be im-
proved. Although this may not always
possible on board, it will in most cases
be possible to do at home. Make sure
it is dark, because darkness is the main
cue for the body to sleep. Also, the
room should be well ventilated and
cool (below 20 degrees) and free of any
sounds that may disturb your

16
sleep: keep it quiet. Do not forget, for
instance, to switch off the phone and
door bell when aiming to sleep during
daytime.
Your sleep practices are another
important aspect. Try, for instance, to
develop a before-sleep routine. This
can help you trigger your sleep mecha-
nism. Relaxing, reading, or listening to
soothing music are among the factors
that can get you ready for sleep. Avoid
taking nicotine or alcohol at least two
hours before sleep, and avoid caffeine
even six hours before sleep. Heavy
exercise should also be avoided for at
least two hours before going to bed,
since this will stimulate your body and
increase your metabolism. If hungry,
try to eat something light before going
to bed.
Napping is an excellent way to coun-
teract fatigue. A planned nap before a
night shift will reduce the performance
degradation during that night shift.
Although you can not store up sleep
by taking more than you need, you can
minimize the impact of fatigue by be-
ing well rested when starting to work.
When you take naps in addition to a
longer sleep period, try to keep them
short (15-40 minutes) to avoid waking
up from a deep sleep. If you plan a nap
before a night shift, however, you can
schedule it to last for two hours and to
end about an hour before you need to
work.
Life style
Not only sleep, but also other life style
choices that affect your overall health
will affect your sleep and fatigue. Here
are some examples of a healthy life
style that also your sleep will benefit
from.
Regular exercise will improve your
health. Stay fit by getting for instance
30 minutes of exercise at least three ti-
mes a week. Walking, jogging or going
to the gym can easily fit into a seafarers
irregular schedule. But do remember
not to exercise within a few hours of
bedtime.
Eating well includes eating regular-
ly. You should eat easily digestible
meals during your body’s biological
night, since digestion is influenced by
your body’s biological clock and will
slow down considerably at night (see
examples in chapter 5). Cold drinks
at bedtime may be more likely to keep
you awake than warm drinks.
Alcohol should be avoided before
going to bed. Although it may help
you to fall asleep, it will disturb your
sleep patterns and cause you to wake
up early or even in the middle of the
night. Alcohol also restricts respiration,
negatively affecting your snoring.
Sleeping pills should be avoided. Na-
tural sleep is best and sleep caused by
sleeping pills is usually abnormal and
less restorative. They may also result in
a variety of side effects such as anx-
iety, nausea, confusion, dizziness, etc.
Furthermore, a rebound insomnia will
occur if you have taken sleeping pills
for a long time, since your body has
become used to the pills to initiate and
maintain sleep.

17
Figure 8. Sources of caffeine.
200
0
20
40
60
80
100
120
140
160
180
Caffeine(mg)
Products
Stimulants
Medication
Food
Vivadrin
Caffedrine
NoDoz
Excedrine
Anacin
Dristan
Teainfused
Instantcoffee
Percolatedcoffee
Dripbrewedcoffee
Decaffeinatedcoffee
Cocoa
JoltCola
CocaCola
PepsiCola
Chocolatebar
Social support might be one of the
biggest challenges for a seafarer where
finding time to spend with family and
friends is difficult. Moreover, family
obligations may often compete with
your need for sleep. First thing to do
is to talk with your family and friends
and explain your situation. Make sleep
a priority followed immediately by
spending time with your family.
Strategies to stay awake
Caffeine is the most commonly used
stimulant used to maintain alertness.
The stimulating effect peaks about
30 minutes to one hour after intake
and it will take 7 to 8 hours before it
is cleared out of your system again.
Caution should be taken due to the
fact that caffeine increases heart rate,
blood pressure, and urination. It is
also addictive and will in heavy users
lead to withdrawal symptoms when
quitting. Be aware that there are many
more substances out there than just
coffee that contain caffeine. (see Figure
8). Avoid them before bedtime, since
they will increase awakenings and
reduce your deep sleep as well as your
sleep duration in general. However,
when planning for a short nap (max 20
minutes, you can take caffeine befo-
re the nap and benefit from the peak
effect when you wake up.
Nicotine has opposite effects depen-
ding on its concentration in your
blood. Whereas low concentrations
will be relaxing, higher concentrations
work as a stimulant. However, the
alerting effects are minimal, if any, and
short. Moreover, smoking contributes
to many health problems like lung
cancer and respiratory diseases.

18
Points to remember
• Improve your sleep environment and sleep practices.
• Adopt a healthy lifestyle without excessive caffeine and alcohol.
• Educate your friends and family about the difficulties of irregular
work.
• Take advantage of the recuperative value of naps.
• Use caffeine wisely and carefully pick the timing and quantity
• Bright light acutely increases your alertness, but should at some
times be avoided.
• Getting up and walking around can give you a short revive.
Bright light has an acute alerting
effect and is even being used to treat
seasonal affective disorder. Be careful,
however, with light exposure outside
the normal daytime, since it will then
shift your biological rhythm either
towards eveningness (when exposed in
the early nightly hours) or morningness
(when exposed in the second half of
the night).
Physical exercise can provide a short
revive, but will not last longer than 15
to 20 minutes. Getting up and moving
around a little bit can easily be done
and without any limitations or side
effects.
Additional strategies have been descri-
bed as well, but their effects have never
been shown. Noise and cool air are,
for instance, widely used, and you may
feel for yourself that they work, but the
effects are minimal if any.

19
5 An overview of tips and hints
Essential strategies
• Know your sleep needs and limitations
• Keep your biological rhythm in mind
• Make sleep a priority
• Start working without any sleep debt
• Watch for the signs of fatigue
• Use alerting strategies at work
• Eat healthy and exercise regularly
• Consult your physician if you think you have a sleep
disorder
Napping tips
• Use longer naps (> 90 minutes) to decrease your sleep
debt
• Use shorter naps (< 40 minutes) to increase your alert-
ness when tired
• Time your naps to your body clock
• Beware of sleep inertia upon wake up
• Do not nap if you have insomnia
Food tips
• Eat healthy and regularly
• Avoid fat and spicy food at night
• Limit caffeine intake
• Avoid caffeine, alcohol, and heavy meals prior to sleep
• Eat a light snack at night

20
Food to avoid on night shifts
Fat food: Fried food
Pastries
Potato and corn chips
Pizza
Whole-milk dairy products
Fatty meat
Stomach irritating food: Spicy food
Excessive coffee or tea
Tomato juice

22
Test 1 Are you a morning or
evening person?

27
Your total score can range from 16 to 86. Scores below 41 indicate evening types,
scores above 59 morning types:
16 - 30 Definite evening
31 - 41 Moderate evening
42 - 58 Intermediate
59 - 69 Moderate morning
70 - 86 Definite morning
Your score should be approximately associated with the following sleep times:

28
Test 2 How sleepy are you at
the moment?
Many tests exist to find out how sleepy you are. Please check out two commonly
used ones.
1. The Karolinska Sleepiness Scale (KSS):
Here are some descriptors about how alert or sleepy you might be feeling right
now. Please read them carefully and CIRCLE the number that best corresponds to
the statement describing how you feel at the moment.
1. Extremely alert
2. Very alert
3. Alert
4. Rather alert
5. Neither alert nor sleepy
6. Some signs of sleepiness
7. Sleepy, but no difficulty remaining awake
8. Sleepy, som effort to keep alert
9. Extremely sleepy, fighting sleep
If you score 7 or higher, you are quite likely to experience micro sleeps, very
short lasting sleeps without you actually being aware of it. Time to nap or adopt
another coping strategy!

29
2. The Epworth Sleepiness Scale (ESS)
If you add up all your points in the ESS and end up above 10, you are likely to
have excessive daytime sleepiness.

30
Test 3 Keep a sleep diary
Improving your sleep starts with keeping track of it. A sleep diary should not
cost you more than 30 seconds to fill in, each morning after the previous night’s
sleep. Do not use it during the night or keep it in your bedroom. Use it only as
a guidance. It will look like the one below (from Division of Sleep Medicine at
Harvard Medical School)
DAY
(Date)
NAPS
(Duration)
BEDTIME
TIMETAKEN
TOFALL
ASLEEP
NUMBEROF
AWAKE-
NINGS
DURATION
OFAWAKE-
NINGS
FINALWAKE
TIME
OUTOFBED
TIME
TIMESPENT
ASLEEP
NEXTDAY
ALERTNESS
(1-10)
MONDAY
TUESDAY
WEDNESDAY
THURSDAY
FRIDAY
SATURDAY
SUNDAY

31
All about sleep at the university of Harvard:
http://healthysleep.med.harvard.edu/
IMO guidance on fatigue:
http://www.imo.org/OurWork/HumanElement/VisionPrinciplesGoals/Pages/
Fatigue.aspx
Fatigue information from SeaHealth:
http://www.seahealth.dk/en/page/fatigue
Watch the seafarers fatigue film from Cardiff University (30 minutes):
https://www.youtube.com/watch?v=ua-ppReV684
Useful links

Stressforskningsinstitutet
www.stressforskning.su.se

fatigue_handbook_a5

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