Posted: January 24th, 2023
In responding to the Assignment Questions, you were expected to provide your personal perspective and experience along with factual responses.
Workload and Automation
Module 6 Presentation
Effective workload management involves numerous factors, including:
Management of automation
Management of available resources
Standard operating procedures.
Factors affecting workload
The nature of the task
The circumstances under which the task is performed
The person and their mental state
Yerkes Dodson Law
This law dictates that performance increases with physiological or mental arousal, but only up to a point. When levels of arousal become too high, performance decreases. The process is often illustrated graphically as a bell-shaped curve which increases and then decreases with higher levels of arousal.
Behavioral markers for CRM
Behavioral markers for CRM reflect how well the crew manages to prioritize tasks, share the workload, and avoid being distracted from essential activities. These include:
Crewmembers speak up when they recognize work overloads in themselves or in others.
Tasks are distributed in ways that maximize efficiency.
Workload distribution is clearly communicated and acknowledged.
Non-operational factors such as social interaction are not allowed to interfere with duties. Sterile cockpit rule is maintained.
Task priorities are clearly communicated.
Reducing Vulnerability to Interruptions & Distractions
Recognize conversation is a powerful distractor
Recognize head down tasks greatly reduce ability to monitor
Schedule/reschedule activities to minimize conflicts between tasks
If performing 2 tasks concurrently scan, don’t become fixated
Treat interruptions as red flags
Explicitly assign responsibilities
Can you think of an example where you, personally, have been completely overloaded either at work or at home?
How did you cope? What mechanisms did you use?
How to delegate
The right person for the job
Balance responsibility and authority
Balance the tasks
Extract from Standards Doc 29
Examples of poor practice:
Flying ‘solo’, in multi-pilot aircraft, without other crew members involved
Allowing secondary operational tasks to interfere with primary flight duties
Inadequate workload planning
Ignoring signs of stress and fatigue
Examples of good practice:
Distributes tasks among the crew, checks and corrects appropriately
Secondary operational tasks are prioritized to retain sufficient resources for primary flight duties
Allocates enough time to complete tasks
Think of workload management as not being dissimilar to triaging a patient.
Check the vitals of the task and concentrate on the most critical task needed to safely complete the mission. Prioritize the tasks you’re called upon to perform in descending order of importance.
In aviation it’s Aviate, navigate, communicate.
In today’s fully automated, glass cockpit environment, the pilot’s role has become more supervisory and the requirement for direct control input is diminished or absent…
When automation functions reliably, as it does most of the time, it can induce pilots to be less alert in monitoring its behavior which can create…
NASA’s Aviation Safety
Reporting System 2005
Perceived problems/concerns identified in the study of flight-deck automation.
Pilots may be out of the control loop and peripheral to the actual operation of the aircraft and therefore not prepared to assume control when necessary.
Manual skills may not be acquired.
Low time pilots assigned to advanced technology aircraft may not acquire manual flying skills, which are still required.
Information overload may exist.
Large amounts of information and/or poor formatting of information may increase pilot workload.
Failure recovery may be difficult.
When automation fails, pilots may have difficulty taking over monitoring, decision-making, and control tasks.
Pilots may be reluctant to assume control.
When automation malfunctions, pilots may be reluctant to assume control which may lead to unsafe conditions.
Controls of automation may be poorly designed.
Automation controls may be designed so they are difficult to access and activate quickly and accurately, or easy to activate inadvertently.
Scan pattern may change.
Display layout in automated flight decks may change the traditional instrument scan pattern, possibly leading to loss of skills which may be needed upon transitioning to conventional aircraft.
Interface may be poorly designed.
The pilot automation interface may be poorly designed with respect to human factors considerations, possibly resulting in poor pilot performance or pilot dissatisfaction.
Mode transitions may be un-commanded.
Automation may change modes without pilot commands to do so, possibly producing surprising behavior.
Pilots may lack confidence in automation.
Pilots may lack confidence in automation due to their experience (or lack of experience) with it. This may result in a failure to use automation when it should be used.
Manual operation may be difficult after transition from automated control.
In some situations flight control may be difficult after transition from automated to manual flight.
Is not easy to identify, nor is it easy to measure
Can have serious consequences both on and off the job
The direct relationship between air and marine accidents and crew fatigue is well documented, but also affects family life, health, and emotional well being
Fatigue affects almost everything humans do, and everyone to some extent. Fatigue is especially dangerous because people are often poor judges of their own level of impairment.
This module will provide you with important about fatigue and sleep, and provide proven techniques to help counteract the effects of fatigue, both at work and at home.
What is Fatigue?
A complex state that includes a lack of alertness and a reduced capacity for mental and physical performance
Fatigue impacts key elements of effective crew resource management (CRM):
Situational awareness (SA)
Fatigue is not just feeling physically tired, it’s also a state of impaired alertness, attentiveness, mental and physical performance. Being fatigued also includes having reduced motor coordination, and slower reaction time. When we are fatigued, there is a loss of environmental awareness, impairment of cognitive/logical reasoning skills, poor judgment and diminished ability to communicate and/or process communications and information.
The International Civil Aviation Organization (ICAO) defines fatigue as:
..a physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical activity) that can impair a crew member’s alertness and ability to safely operate an aircraft or perform safety-related duties. (From TSS Safety Most Wanted)
ICAO definition of Fatigue
A physiological state of reduced mental or physical performance capability, resulting from sleep loss or extended wakefulness, that can impair a crewmember’s alertness and ability to safely operate an aircraft or to perform safety related duties
ICAO definition of Fatigue
Some facts about fatigue
Approximately 38% of the U.S. workforce have experience fatigue within the past two weeks
9% of the U.S. workforce lost productive work time as a consequence of fatigue
More important is the impaired concentration that leads to increased time to complete tasks and increased safety risks
Shiftwork and alternative work schedules such as night shift and extended hour work shifts increase fatigue risks
Most people believe that fatigue is a safety issue or a factor that negatively affects work performance. The occurrence of fatigue is more common than some people realize and it can have some very negative consequences for those who experience it. In a recent study of the US workforce, researchers wanted to find out what percentage of workers experienced fatigue at least once in the last two weeks. What percentage of the people in the general workforce population do you think responded yes, that they had been fatigued at least once in the last two weeks?
On the surface of things, fatigue seems fairly straightforward. We all get tired, do what we need to do to get through it, and then catch up on our sleep when we can. We still harbor a cultural mentality of mind over matter, and of human failing if one allows him/herself to get tired to the point of being unfit for duty. After all “if our people spent more time in bed getting their proper rest (and less time watching TV, sitting in a bar, or allowing themselves to be compromised by family life and personal activities), then they wouldn’t be tired on the job!” In other words, from a management perspective, fatigue is often perceived to be a behavioral problem, caused more by personal irresponsibility than by other factors (and certainly not by our operating policies and procedures). Well, those of us who have lived and worked shiftwork know better. Just try sleeping in the daytime or rotating back and forth from days to nights for an extended period and see how much “proper rest” YOU can get!
Human fatigue has been indicted as a factor in numerous historical aircraft accidents, as well as several recent AMO accidents. It has been estimated that fatigue contributes to 20-30% of transport accidents. In commercial aviation operations, about 70% of fatal accidents are related to human error, therefore the risk of crew fatigue contributes to about 15-20% of the overall accident rate. (From TSS Safety Most Wanted)
Two types of fatigue
Acute fatigue – can occur in a matter of hours due to excessive physical or mental exertion
Chronic fatigue – occurs when the normal period of rest is insufficient for restoring an individual’s work performance to its usual level
Persons suffering from chronic fatigue always perform below their personal best.
Workplace and Personal Factors Contributing to Fatigue
Different people will experience fatigue in slightly different ways: symptoms will be different from one individual to another. Our tolerance for different levels of fatigue, as well as our ability to recover from the effects of fatigue will also be different from one person to another. Despite these differences, the risks presented by unmanaged or unmitigated fatigue are just as serious.
Fatigue results in operator inefficiencies such as ……
There is a wide-range of contributing factors can increase the risk of fatigue. Some factors are work based and some personal:
Inadequate sleep for repair and recovery of the body (in each 24 hour period)
Shift work (working out of sync with the natural body clock)
Extreme physical or mental exertion
lifestyle, family responsibilities, ill health.
Fatigue is a workplace hazard, even though someone’s fatigue may be the result of work or out of work factors. As with other workplace hazards, management and individuals need to work together to reduce the risk and impact of fatigue. Fatigue is a workplace hazard because it affects your ability to think clearly and act appropriately. Fatigued workers are less alert, don’t perform well, are less productive and are more likely to have accidents and injuries.
People who do shift work and air and marine craft operators are particularly at risk of fatigue because their natural body clock and sleep rhythms are disrupted.
Tiredness is a symptom of fatigue. However, sometimes a fatigued person may feel wide awake and engaged in a task. The primary cause of fatigue is a lack of sleep. Good restful sleep, free from drugs or alcohol is a human necessity to prevent fatigue. Fatigue can also be caused by stress and overworking. A person’s mental and physical state also naturally cycles through various levels of performance each day. Variables such as body temperature, blood pressure, heart rate, blood chemistry, alertness, and attention rise and fall in a pattern daily. This is known as one’s circadian rhythm. A person’s ability to work (and rest) rises and falls during this cycle. Performance counter to circadian rhythm can be difficult. Until it becomes extreme, a person may be unaware that he or she is fatigued. It is easier recognized by another person or in the results of tasks being performed. This is particularly dangerous in AMO since the lives of people depend on performance at a high level of proficiency. Working alone when fatigued is particularly dangerous.
The Role of Stress in Fatigue
Stress is a state of mental or emotional strain or tension resulting from adverse or very demanding circumstances to the extent that one’s ability to adapt and respond is difficult or impossible.
Stressors can be broken down to include physical, mental, emotional or environmental
Totally eliminating stress is neither possible nor desirable – it needs to be identified and managed
In small doses, stress is a good thing. It can energize and motivate you to deal with challenges. But prolonged or excessive stress — the kind that overwhelms your ability to cope — can take a severe psychological and physical toll. High stress levels have been linked to depression, anxiety, cardiovascular disease, musculoskeletal problems, impaired immune response and cancer.
Your genes, personality and life experiences all influence the way you respond to and cope with stress. Situations and events that are distressing for most people might not bother you in the least. Or, you may be particularly sensitive to even minor stressors. The first step in coping with stress is identifying your stress triggers.
Some causes of stress are obvious — the threat of losing your job, for instance. But small, daily hassles and demands such as a long commute or difficult co-workers also contribute to your stress level. Over time, small, persistent stressors can wreak more havoc than sudden, devastating events do.
(Source: Mayo Clinic – http://www.mayoclinic.com/health/coping-with-stress/SR00030)
Complete prevention of stress is neither possible nor desirable, because stress is an important stimulus of human growth and creativity, as well as an inevitable part of life. In addition, specific strategies for stress prevention vary widely from person to person, depending on the nature and number of the stressors in an individual’s life, and the amount of control he or she has over these factors. In general, however, a combination of attitudinal and behavioral changes works well for most people. The best form of prevention appears to be “parental” modeling of healthy attitudes and behaviors within the person’s environment (work, family, etc.). (source: http://medical-dictionary.thefreedictionary.com/stress)
Both cognitive and emotional stressors such as boredom, uncertainty, worry, fear, loneliness, lack of a social support network, and vague feelings of helplessness and lack of control also have the potential to precipitate the development of mental stress and adversely impact an operator’s calm and sense of well-being. In some situations, stress responses can be lifesaving because they provide the extra energy necessary to successfully accomplish a hazardous operational activity, succeed at a task, or escape danger. In other situations, stress can be life threatening, especially when the stress is chronic or in response to intangible or perceived threats.
Stress can result from a variety of causes in operations, including fatigue from physical and mental factors such as long work schedules, demanding tasks, changing work shifts, sleep deprivation, difficult missions, noise and weather conditions. Certain mission requirements can also lead to stress. For example, it is more stressful to perform tasks dependent on good visibility when operations are conducted at night, and the requirement to wear protective clothing can complicate completion of even the most straightforward tasks. In addition, there is frequently emotional stress from being separated from loved ones, coupled with concern for their wellbeing while TDY.
Any combination of these factors can lead to severe decrements in cognition and mood. When combined with pervasive fatigue, performance may be significantly worsened. It is important to remember, however, that different operators will be affected by stress differently, and it is important for leaders at all levels to be aware of those individuals who might have more severe external stressors.
Clearance Authorities should assume both physical and mental stress are present to some degree in all Branch/Unit personnel. Observable changes will depend on the individual and his or her personal experiences and appraisal of the situation, but generally, when the mind perceives a stressful event, the body automatically begins the biological “fight or flight” stress response (releasing adrenaline, tensing muscles, boosting heart rate, constricting blood vessels, slowing the digestive system, causing “tunnel vision,” etc.). Without proper rest, exercise and nutrition to counteract these effects, the body continues producing the stress response until it is fatigued or exhausted.
Reactions to Stress
Normal reaction to stress
Responding rapidly and exactly, within the limits of their experience and training. Many responses are automatic, which points out the need for proper training
Extremely sensitive to all aspects of the surrounding environment
Abnormal reaction to stress
Inadequate, random, or illogical response, or doing more than is called for by the situation
Marked fluctuations in mood or emotion, such as laughter at inappropriate times, extreme over-cooperation, or anger
NORMAL REACTIONS TO STRESS
When a threat is recognized or imagined, the brain alerts the body. The adrenal gland activates hormones which prepare the body to meet the threat, or to retreat from it. This often is called the fight or flight syndrome. The heart rate quickens, certain blood vessels constrict to divert blood to the organs which will need it, and numerous other physiological changes take place. Normal individuals begin to respond rapidly and exactly, within the limits of their experience and training. Many responses are automatic, which points out the need for proper training in emergency operations prior to an actual emergency. The affected individual thinks rationally, acts rapidly, and is extremely sensitive to all aspects of the surroundings.
ABNORMAL REACTIONS TO STRESS Reactions to stress may produce abnormal responses in some people. With them, response to anxiety or stress may be completely absent or at least inadequate. Their responses may be random or illogical, or they may do more than is called for by the situation. During flight instruction, instructors normally are the only ones who can observe students when they are under pressure. Instructors, therefore, are in a position to differentiate between safe and unsafe piloting actions. Instructors also may be able to detect potential psychological problems. The following student reactions are indicative of abnormal reactions to stress. None of them provides an absolute indication, but the presence of any of them under conditions of stress is reason for careful instructor evaluation.
Definitions of Stress
A state of mental, emotional, or other strain (Oxford Dictionary)
An adverse reaction to excessive pressure or other types of demand (HSE)
Any physical, psychological or social pressures, that when applied to a system, causes some significant modification of its form. Stress results from the imposition of any demand or set of demands which require us to react, adapt or behave in a particular manner in order to cope with or satisfy them (CAP 737)
Definitions of Stress
4 Major Types of Stress
Eustress – Short term provides immediate strength.
Hyperstress- Pushed beyond limit.
Lack of control or disruption of events
Anxiety over courses / checks
Home to work interface
Career prospects and achievements
Lack of responsibility and decision making
Fatigue and Chronic Stress
Chronic stress can result in physical difficulties such as back pain, headaches, gastrointestinal upset, increased blood pressure, irregular heartbeat, and difficulty fighting off infection or disease, all of which can contribute to an individual’s overall fatigue level. In addition, stress can adversely affect an operator’s ability to get sufficient quality sleep, further compounding the fatigue cycle. Stress-related fatigue represents a significant threat to operational effectiveness and can lead to mission failure.
Fatigue can also be detrimental in one’s personal life and is often correlated with increased health issues, impaired driving performance, and difficulties dealing with home and social life. Working non-traditional hours may have negative implications for health. When compared to daytime workers, those working shifts or extended hours tend to have a higher number of health complaints, greater use of sick leave, and more visits to the doctor. Workers with non-traditional shifts also report greater stress, higher alcohol and drug use, greater weariness, and a lower sense of overall well-being.
Chronic stress contributes to an individuals overall level of fatigue, and acute stress can worsen already existing fatigue-related problems. In addition, stress can produce physical complaints such as back pain, tension headaches, gastrointestinal upset, increased blood pressure, irregular heart beats, and difficulty fighting off infections or disease.
There are many signs and symptoms that may indicate fatigue. The symptoms generally fall into one of these three categories: physical, mental, or emotional. It’s important to note that that these are the most common examples of symptoms, not an exhaustive list. Also, these symptoms don’t necessarily indicate fatigue; rather, a collection of symptoms signifies that a person is experiencing at least some level of fatigue.
Additional Information if needed:
Evidence suggests that fatigue and irregular sleeping patterns can disrupt the body’s natural processes. For instance, the circadian rhythm plays a role in digestion, which results in workers with non-traditional working hours being four to five times more likely to develop a gastrointestinal disorder such as peptic ulcers, indigestion, heartburn, flatulence, upset stomach, or constipation. The digestive system slows at night making it more difficult to digest food. Workers who have extended work hours tend to eat at irregular times which can lead to an increase in digestive issues.
Working non-traditional hours is associated with greater incidence of heart disease and high blood pressure. It is believed that it may be partially due to increased stress that often accompanies these work schedules. It is especially important to be familiar with one’s family history. Diet, exercise, not smoking, and especially getting enough sleep are some of the most effective things a person can do to prevent cardiovascular disease from developing.
There is evidence to suggest that workers experiencing fatigue may be more susceptible to disorders such as depression and anxiety. It is believed that this may be related to difficulty balancing work with family and social life. Unfortunately, this can become a very negative cycle as fatigue is often considered a result of depression and anxiety.
Changes in behavior when fatigued or stressed
Difficulty concentrating and thinking clearly
Poor and careless performance
Greater tolerance for error
Inattention to minor, but potentially important, details
Increased lapses of attention
Decreased motivation and conservation of effort
Mental fatigue comes from a combination of poor sleep, circadian rhythm or “body clock” disruptions, or intense mental activity (e.g., short notice, prolonged planning sessions for critical missions, or tasks requiring intense concentration).
Mental symptoms of fatigue can include: difficulty concentrating, attention lapses, poor communication, poor anticipation, mistakes, forgetfulness, unclear thinking and poor decision making. Lapses in attention or making mistakes even on well-practiced tasks can result in serious errors (as seen in ASRS reports of fatigue).
Symptoms of fatigue may also include short-term memory problems, channeled concentration on unimportant issues while neglecting other factors that may be more important, and failure to maintain situational awareness. A fatigued person may be easily distracted or may be nearly impossible to distract. Fatigue results in an increase in mistakes, poor judgment, and poor decisions or perhaps no decision at all. A fatigued person may also lower his or her standards.
Physical Warning Signs of Fatigue
Lack of energy, weakness, or light-headedness
Heavy eyelids or micro-sleeps
Nodding off or head-drooping
Headaches, nausea, or upset stomach
Slowed reaction time
Physical symptoms can include things like: yawning, heavy eyelids, eye-rubbing, nodding off, headaches, nausea, slowed reaction times and lack of energy. Nodding off and micro sleeps can be especially dangerous when performing safety-critical tasks or operating machinery.
Reaction time increases, Slower to notice problems and Less smooth control of aircraft, vessel, vehicle or equipment
Emotional Warning Signs of Fatigue
More quiet or withdrawn than normal
Lack of motivation to do the task well
Irritable or grumpy with colleagues, family, or friends
Heightened emotional sensitivity
Fatigue also affects mood. A fatigued person may experience abnormal mood swings. People who do not get enough sleep are more likely to get impatient or agitated, and they have difficulty getting along with others. Increased irritability and stress negatively influences personal, work, and family relationships, resulting in inadequate/ineffective communications, and correlating with increased absenteeism and turnover as well as reduced morale and poorer labor relations. Industrial surveys reveal that absenteeism rates are nearly double in facilities with severe fatigue problems, as compared to facilities where fatigue is not a problem (Aguirre and Moore-Ede, 2008) and (National Sleep Foundation (2002)
Emotional symptoms of fatigue can include symptoms such as withdrawal, lack of motivation, irritability, low morale and emotional sensitivity. Emotional symptoms are especially likely to be problematic in social situations and influence how a person approaches or deals with coworkers, friends, and family.
Effects of fatigue on attention and vigilance
Fail to pay attention to important details
Leave out steps in tasks or fail to return to tasks when distracted
Preoccupation with single task or steps
Tunnel vision, less likely to notice the unexpected
Less aware of poor performance
Concentration requires more effort
Increase likelihood of detecting a threat to safety
While fatigue is biological, environmental factors such as continuous work time without a break or the intensity of work demands can also influence the way in which fatigue is expressed. Sometimes, workload can temporarily mask the feelings of fatigue. You may have experienced this when your fatigue expresses itself only once you begin a monotonous task such as surveillance. It’s important to remember that while fatigue can be masked by aspects of the workload, the biology that causes it remains.
Mental symptoms of fatigue can include: difficulty concentrating, attention lapses, poor communication, poor anticipation, mistakes, forgetfulness, unclear thinking and poor decision making. Lapses in attention or making mistakes even on well-practiced tasks can result in serious errors (as seen in ASRS reports of fatigue).
Notes if needed for script:
Attention is a limited resource, so selective attention allows us to tune out unimportant details and focus on what really matters. Selective attention can be conscious or unconscious. Often a person can be selectively attending to an object without realizing it, especially if he or she is expert in the particular task where attention is required.
Attentional control refers to an individual’s capacity to choose what they pay attention to and what they ignore. It is also known as endogenous attention or executive attention. In other words, it can be described as an individual’s ability to concentrate. Primarily mediated by the frontal cortex area of the brain, attentional control is thought to be closely related to other executive functions such as working memory.
Vigilance is a concept closely related to selective attention (the process of focusing on a particular object in the environment); in fact, the word attention is often used when defining vigilance. One definition of vigilance describes it as the process of paying close and continuous attention. It is often described as a quality or state of alertness or watchfulness. Vigilance can also be thought of as the extent of readiness to detect, or the likelihood of detecting, a stimulus that is imperative to safety.
Impact of Fatigue on Performance
Effects of fatigue on hand-eye coordination closely resembles the effects of alcohol impairment:
After 17 hours of continued wakefulness, performance is consistent with someone with a blood alcohol content of .05
After 24 hours of continuous wakefulness, performance is similar to someone with a blood alcohol content of .10 (considered legally drunk and too impaired to operate a vehicle)
There is scientific evidence that suggests when we’re tired (or mentally fatigued) our ability to perform the simplest of tasks is impaired to the same level as if we were legally intoxicated (Dawson and Reid, 1997).
The effect of fatigue on hand-eye coordination closely resembles the effects of alcohol. In fact, generally, the longer an individual has been awake, the more their performance is impaired. One study showed that after approximately 17 hours of continuous wakefulness, performance is consistent with someone with a blood alcohol content of .05, and after 24 hours of continuous wakefulness, performance is similar to someone with a blood alcohol content of .10! That is considered legally drunk and too impaired to operate a vehicle.
The number of fatigue-related accidents is considerably higher at night than during daytime (Mitler 1988). In fact, a study found that drivers are 50 times more likely to fall asleep at 2 am than at 10 am (Horne and Reyner, 1995). No matter how well trained, skilled, motivated, or experienced, operators are frequently compromised by fatigue. Behavior becomes erratic and deviant…not willfully, but because of our physiological nature. As a result, incidents are often misdiagnosed as being due to behavioral problems, when they are actually physiological in nature. Thus, understanding human physiology is key to successfully identifying, and managing the inherent problems of shiftwork and fatigue-related human error.
Biological Clock: Exogenous Factors
The clock maintains a 24-hour day if exposure to day/night is consistent. Entraining agents or zeitgebers
Timing of activity, meals, etc. provide cues for regulating the clock.
Influences the timing of exposure to daylight
The circadian (body clock) and sleep factors are inherent (Moore-Ede, 1982, Akerstedt, 1995). Human biology has been “hardwired” since the beginning of humankind. This did not become an issue until the development of electricity in the 1880’s which ushered in the modern era of shiftwork and compromised our physiological “design specifications”. As a result, our shiftworkers have had to endure a dysfunctional state of being for the past 120 years… a state of being unknown to our primitive ancestors, and one which negatively impacts our performance and reliability.
Both the circadian and sleep factors are impacted by the operational necessity to keep the equipment running 24-hours per day (e.g. automation, continuous process, asset utilization, reduced unit costs, improved customer service, etc…). Work and environmental factors, on the other hand, are influenced by counter-productive management attitudes, policies, practices and operating procedures that often detract from human performance, rather than support it (e.g. by lack of human factors knowledge/understanding), by confusing human physiology with human behavior, by managing for the convenience of day managers to the inadvertent detriment of the
shiftworkers, etc.).Our body’s internal clock is kept on correct time by exposure to light, particularly early morning light. Our CRs are so reliable that even if we are removed from the 24-hr. rhythm of night and day (such as wintering in Antarctica) the rhythms continue to run. Without regular exposure to daily cycle of light and dark, CRs eventually begin to “free run” and will no longer align closely with the 24-hr. day. CRs have an important role in regulating sleep patterns. Chemical changes occur in the body as it prepares for sleep, typically between 8 pm and midnight. Body temperature reaches a low point at around 3 am, then begins rising steadily, apparently as our body gets ready for the day ahead, even before most people are naturally awake.
Biological Clock: Endogenous Factors
Circadian Rhythms persist without time cues
Slow to change – Takes at least 3 days to fully recover from a change in work schedule or time zone changes
Without time cues our biological clock runs on a 24-25 hour day cycle
A circadian rhythm is any biological process that displays an endogenous (originate from within an organism, tissue, or cell), entrainable (can be reset by exposure to external stimuli such as light and heat) oscillation of about 24 hours. These 24-hour rhythms are driven by a circadian clock.
The rhythm has an endogenous free-running period that lasts approximately 24 hours. The rhythm persists in constant conditions, (i.e., constant darkness) with a period of about 24 hours. The period of the rhythm in constant conditions is called the free-running period. The rationale for this criterion is to distinguish circadian rhythms from simple responses to daily external cues.
The rhythms exhibit temperature compensation. In other words, they maintain circadian periodicity over a range of physiological temperatures. Many organisms live at a broad range of temperatures, and differences in thermal energy will affect the kinetics of all molecular processes in their cell(s). In order to keep track of time, the organism’s circadian clock must maintain roughly a 24-hour periodicity despite the changing kinetics, a property known as temperature compensation
Some features of the human circadian 24 hr. biological clock
Here are some features of the human 24 hr. biological clock. Circadian rhythmicity is present in sleeping and feeding patterns. There are also clear patterns of core body temperature, brain wave activity, hormone production, cell regeneration, and other biological activities. A better understanding of these features assists in understanding the impact of CR on scheduling of work and movement across time zones.
Biological clock affects the daily rhythm of many physiological processes. This diagram depicts the circadian patterns typical of someone who rises early in morning, eats lunch around noon, and sleeps at night (10 p.m.). Although circadian rhythms tend to be synchronized with cycles of light and dark, other factors – such as ambient temperature, meal times, stress and exercise – can influence the timing as well.
Source: “The Body Clock Guide to Better Health” by Michael Smolensky and Lynne Lamberg; Henry Holt and Company, Publishers (2000).
Beware of the Window of Circadian Low (WOCL)
Mental functioning is generally at its worst from 2:00 am-5:00 am when we would normally be asleep
Another surge in potential for human error occurs after lunch until 3:00 pm (post-lunch dip)
Even people without a sleep deficit find work performance affected by fatigue during these periods—but a sleep deficit will intensify effects
Thus, the biological clock regulates the daily availability of physical energy and mental resources. The daily environmental rhythm of daylight and darkness is the time-giving cue that regulates the biological clock. As daylight energizes the retina in the back of the eye, a neural message is conveyed to brain centers and glands that make up the human biological timing system. The availability of mental and physical resources fluctuates during the 24-hour day. The best and worst times of day are determined mostly by light cues received by the body clock.
Sleep loss and circadian rhythm
Physiological fatigue is a biological process that depends on the interaction between sleep loss and the circadian rhythm (CR)
CR is the human body’s internal clock and is intimately related to sleep and fatigue.
CR approximates a 24 hour cycle and it is set primarily by daylight
There are two distinct components or ways to talk about fatigue, either physiological or subjective. Physiological fatigue is a biological process that depends on the interaction between sleep loss
and the circadian rhythm. The circadian rhythm is the human body’s internal clock and is intimately related to sleep and fatigue. It approximates a 24 hour cycle and it is set primarily by daylight.
Together, these factors contribute to the body’s response to the physiological need for sleep, which is to try to sleep. The only way to reverse physiological fatigue is through sleep.
Subjective fatigue on the other hand is based on how a person feels and how fatigued he/she reports feeling. In a sense, this is still physiological fatigue, but can often be masked by motivation,
caffeine, physical activity, and environmental stimulation. These factors influence the level off fatigue that is reported, but not the underlying physiological fatigue that is present.
Fatigue is very difficult for people to reliably estimate, especially when they are fatigued! Often subjective measures of fatigue are much more optimistic than physiological measures. This
means that on average, a person is probably more fatigued than he/she realizes and therefore, present a bigger safety threat than they realize.
Shift Work Changes
Day, Mid, Night, & Rotating
Time Zones Changes
East-bound (greater impact
West-bound (less impact)
Shiftwork/Time zone Changes
We have this notion that, like our equipment, employee work capacity is a lineal function, that 80 hours of work will yield 80 hours of productive output (actually, it nets 50-55 hours depending on the level of employee interaction with the mission (Nevison, 2001, Dembe, et al. 2005).
While today’s sophisticated equipment and machinery is quite lineal and actually designed to operate non-stop for long periods of time. We humans are not.
So management’s thinking that one should be able to work as many days in a row as they (or we employees) would like without any significant problem or loss of performance, and the organization is happy to let us do it! Overtime saves having to hire more people and paying all those costly benefits (actually the National Average is only 32%, as opposed to the 50% premium we pay for overtime), and it sure makes a supervisor’s job a whole lot easier to fill absences, vacations and other benefit days off by dishing out the overtime to those who want it.
Fatigue levels tend to be higher at the midpoint and end of a work shift than other times of day. In industry, the probability of mistakes or accidents nearly doubles during the 10th, 11th and 12th hours of 12-hour shifts compared to the risk observed at 8 hours.
After rotating into nighttime shiftwork or after traveling across time zones, the symptoms of fatigue, sleepiness, and lack of motivation are indications that circadian desynchronosis has set in. These body clock disruptions increase the mission risk level and can compromise safety. Studies of circadian rhythm disruption on the performance of night shift workers and long distance travelers show a consistent reduction in work efficiency and, in some cases, safety. For example, truck drivers have been shown to have twice as many accidents between 2400 and 0200 compared to during the day. Locomotive operators have an increased probability of missing warning signals when working night shift. Night shift workers perform worse on vigilance tasks and reaction times when compared to day workers. Aviators flying in flight simulators at night have reduced hand-eye coordination, poorer vigilance and calculation proficiency, and impaired flight performance compared to day fliers.
The external stimulus used to “entrain” a rhythm is called the Zeitgeber, or “time giver”. Travel across time zones illustrates the ability of the human biological clock to adjust to the local time; a person will usually experience jet lag before entrainment of their circadian clock has brought it into sync with local time.
Shiftwork and operational performance
Changing from day to night shift often implies a period of 20–24 hours without sleep.
Morning types have a higher homeostatic response to sleep disruption than evening types.
Workers who are extreme morning types should choose their schedules carefully with regard to preserving sleep.
Remember — it takes at least 3 days to fully recover from a change in work schedule changes or when TDY to other time zones.
Over the past 25 years, extensive research has confirmed that fatigue, as related to shiftwork, is fundamentally a physiological problem, not a behavioral one. Certainly, one’s behavior can induce or compound fatigue, but with most operators this is the exception and not the rule. Sleeping during the biological day, either due to shift work or time zone crossings, could lead to insomnia or shortened sleep periods.
Shiftworker fatigue is caused primarily by four operationally driven factors:
1. Circadian (Body Clock) Factors
a. Working when you would normally be asleep
b. Sleeping when you would normally be awake
c. Frequently having to change your sleep/wake cycles
d. Misalignment of daily alertness cycles with work requirements
2. Sleep Factors
a. Inability to get normal hours of sleep
b. Inability to get normal quality of sleep
c. Inability to get consistent bedtime routines
d. Having inadequate sleep environment
3. Work and Environmental Factors
a. Having early shift start times
b. Having fast rotating schedules and/or long, irregular hours (i.e. overtime)
c. Having inadequate rest/recovery time between shifts and/or work blocks
d. Having boring/monotonous work environment
e. Having boring/monotonous jobs
4. Health Factors
a. Medical sleep disorder problems
b. Underlying health issues (e.g. hypertension, diabetes, epilepsy, etc.)
c. Improper timing and content of food (i.e. building cardiac risk factors, digestive
d. Use/abuse of coping substances (e.g. caffeine, sleeping pills, alcohol, etc.)
e. General lifestyle issues
Desynchronosis and Hazard Identification
Crew members are at risk anytime the work schedule and sleep/wake cycle are shifted suddenly
Operational schedules may not provide sufficient warning to implement a carefully organized set of coping strategies and some degree of desynchronosis may be inevitable
Indicators of desynchronosis:
Body sways upon standing
Walking into objects
Degraded personal hygiene
Loss of concentration during briefings
Understanding how to manage shiftwork, in general, and to manage fatigue and alertness levels, in particular (i.e. lack of shiftwork lifestyle training and education). The net results have been chronic ill health, inherent safety issues, broken families (i.e. higher divorce rates), and reduced performance (U.S. Office of Technology Assessment, 1991). The circadian desynchronosis or maladaptation is the syndrome underlying the symptoms of jet lag and shift lag. Classic symptoms include fatigue, malaise, sleepiness, lack of motivation, confusion, and digestive disorders. The most difficult challenge to the body clock occurs during the transition from the day shift into the early morning shift or into nighttime duty hours. This condition is called shift lag because the timing of the body clock always lags behind the sudden change in work/rest schedule.
Do shift workers adapt to permanent night shifts? Not usually. Research shows that fewer than 30% of permanent night shift workers actually adjust their rhythms to a nighttime schedule. In most cases, they remain on a typical daytime pattern (Robertson, S. & Folkard, S. (2006). As a result, even workers on a regular nightshifts will still experience a strong drive for sleep during the night, and will find it more difficult to obtain good quality rest during daylight hours.
Driving to work early in the morning, while on duty, or after a shift?
Most crashes or near misses occur between these time groups:
4:00 – 6:00 a.m. Midnight – 2:00 a.m. 2:00 – 4:00 p.m.
Sleep deprivation greatly increases the risk of a sleep-related crash.
People sleeping less than 5 hours increase their risk four to five times
People who sleep 6-7 hours a night are twice as likely to be involved in a crash as those sleeping 8 hours a night
No matter how well trained, skilled, motivated, or experienced, operators are frequently compromised by fatigue, not willfully, but because of our physiological nature.
Following long shift, remember that 17 hours of continuous wakefulness, performance is consistent with someone with a blood alcohol content of .05
Research shows shift workers are 6 times more likely to be involved in a fatigue-related road crash than any other workers.
Sleep deprivation/restriction: When an individual does not obtain a full 7-8 hours of sleep, the sleep he or she does receive is generally deeper than normal sleep. Awakening from deep sleep is more difficult, and sleep inertia (grogginess) is higher than when normal adequate sleep is obtained. This should be taken into consideration before driving to work. The number of fatigue-related accidents is considerably higher at night than during daytime (Mitler 1988). In fact, a study found that drivers are 50 times more likely to fall asleep at 2 am than at 10 am (Horne and Reyner, 1995). No matter how well trained, skilled, motivated, or experienced, operators are frequently compromised by fatigue. Behavior becomes erratic and deviant…not willfully, but because of our physiological nature. As a result, incidents are often misdiagnosed as being due to behavioral problems, when they are actually physiological in nature. Thus, understanding human physiology is key to successfully identifying, and managing the inherent problems of shiftwork and fatigue-related human error.
Adults between 18-29 are much more likely to drive while drowsy compared to other age groups.
Men are more likely than women to drive while drowsy and almost twice as likely to fall asleep while driving
Who Can Best Judge Level of Fatigue?
Fatigue can be difficult to reliably self-assess
Subjective fatigue is based on how a person feels and how fatigued they report feeling
Fatigue is often more easily recognized by others or by the results of the tasks being performed
Others who may better assess level of fatigue:
Fellow crew member
Coworker or good friend
People are notoriously bad judges of their own level of fatigue. Asking a fatigued person if they are OK to keep working is like asking someone who is drunk if they are OK to drive. Even if we are not good judges of how tired we are, we can still keep track of how long we have been awake, how much sleep we have had recently, and the quality of that sleep. More often a knowledgeable supervisor, fellow crew member, coworker or family member can more accurately assess fatigue levels.
The Samn-Perelli 7- point scale for assessing fatigue
Fully alert, wide awake.
Very lively, responsive, but not at peak.
Okay, somewhat fresh.
A little tired, less than fresh.
Moderately tired, let down.
Extremely tired, very difficult to concentrate.
Completely exhausted, unable to function effectively.
It’s not unusual to hear the words “sleepiness” and “fatigue” used interchangeably. Sleepiness is an important component of fatigue, but fatigue is actually more than that. It can be useful to think of fatigue as a complex state, usually accompanied by drowsiness, in which alertness, mental function and physical performance are all reduced.
The causes and effects of fatigue can also be complex – you may have experienced this for yourself at some point. Even in routine operations, there are a number of factors that can contribute to fatigue.
The Karolinska Sleepiness Scale
Alert – normal
Neither alert nor sleepy
Sleepy, but no effort to keep awake
Very sleepy, great effort to keep awake
Pros and Cons of Subjective Scales
Advantages of subjective scales:
• quick and easy to administer
• either paper-based or computer-based
• minimal disruption to the aircrew
• many studies have used the SPS and KSS, and provide data for comparison
Disadvantages of subjective scales:
• relatively easy to cheat
• may lack face validity
• do not always reliably reflect objective performance measures
When are they useful?
Looking at a lot of crew members
Identifying where problems might exist
As one of several measures
Included on Fatigue Report Forms
Identify times of higher fatigue risk
Monitor effectiveness of mitigations
Tips for preventing fatigue and/or mitigating the effects of fatigue
Improve the quality of your sleep
Time of day
Use of caffeine
Monitor fellow crewmembers for signs/symptoms
Improve your Quality of Sleep: a. Stay close to your duty sleep schedule, even on your days off.
b. Promote a good sleeping environment (cold, dark, and quiet)
c. Avoid large meals, alcohol, and caffeinated beverages within 2 hours of bedtime.
d. Avoid excessive alcohol; although it may improve sleep onset, it will interfere with overall sleep quality.
Time of Day: Be especially mindful of fatigue exposure when working between the hours of 0000 and 0600 (circadian low).
Use of Caffeine: Used properly, caffeine can counter the effects of fatigue. Used improperly it can cause insomnia, contribute to health problems and aggravate fatigue.
Monitor Fellow Crewmembers for the Signs and Symptoms of Fatigue:
a. Unusually quiet
c. Unable to focus/easily distracted
e. Slow reaction times
Myth or reality?
Five or six hours of sleep a night is generally enough.
Very few people can manage on this amount of sleep without being seriously affected.
Daytime sleep is just as good as night time sleep.
Shift workers who have to sleep during the day generally get lower-quality sleep, and less of it.
We can judge how fatigued we are accurately.
Studies have shown that fatigued people don’t realize that their abilities are impaired by fatigue.
We need less sleep as we get older.
We still need the same amount of sleep, but our sleep becomes more fragmented, and we tend to wake up earlier.
Here are some myths related to sleep…..
The average adult needs 7-9 hours of restful sleep during each 24-hour period to maintain the highest level of alertness and performance. Failure to obtain this amount of sleep rapidly and progressively impairs mood, cognition and performance. Remaining awake much longer than 17 continuous hours produces acute fatigue, which diminishes mental capabilities and vigilance. Some studies have shown that some individuals are exceptions and may be far less affected by sleep loss and fatigue than others. Still, the best advice remains that leaders ensure everyone gets sufficient sleep and rest throughout the mission to keep fatigue at bay.
2. Poor quality sleep, which is caused by interruptions to the sleep cycle, ie waking often. Not enough sleep, which is caused by not getting to sleep, being awake for long periods, sleeping only in 3-4 hour blocks
3. Studies have shown severely sleep-restricted individuals are unable to reliably judge their level of fatigue impairment, and the sleepier they become, the more likely they are to underestimate their own sleepiness.
4. Depth of sleep decreases with age, making sleep more fragile in older persons than their younger counterparts. Therefore, environmental factors could lead to more frequent awakenings in older individuals.
Some people see fatigue as a normal and unavoidable part of OAM operations. They consider that with enough effort, a tired worker can continue to perform their job effectively. Increased effort or concentration might help for a few minutes, but it can’t compensate for fatigue over an entire shift. Sleep is a physiologic need like hunger and thirst. Inadequate sleep leads to fatigue that creates generalized decrements in performance, increased safety risks and adverse health consequences.
An individual can continue to work for only a limited time before the need for sleep overrides all else. The person then must sleep in order to continue functioning; sleep is the remedy for acute fatigue. However, it is important to remember that just as all operators have different physical and mental abilities, the same is true regarding the individual effect of sleep deprivation. Leaders at all levels, therefore, need to be as aware of this capability as they are of other strengths and weaknesses. Fatigue has a very real detrimental impact on safety in OAM operations. Sleep debt builds up when someone regularly has less sleep than they need, and sleep debt leads to fatigue.
Your answers to the following questions can help you assess how likely you are to be at risk due of fatigue:
How much sleep have I been getting over the last few nights?
How long have I been awake?
Will I be working at a time when I would rather be sleeping?
Have I had good-quality sleep?
Adults generally sleep between 7-8 hrs. per night, although the need for sleep varies between people, with some individuals needing up to 10 hrs. per night to remain alert. Before the widespread use of electric lighting, people typically slept 9 hrs.—Today, family demands, work commitments, and the use of electronic devices combine to limit the opportunities for a full nights sleep. A large number of people are suffering from sleep deprivation, which can affect health and ability to perform at full performance level.
If we obtain less sleep that we need, we build up a performance deficient level—each successive night adds to the debt. Even reducing our normal sleep pattern by just one hr. each night over several nights can reduce our mental efficiency.
Shift workers, who sleep during daylight hours, also build up a sleep debt because daytime sleep tends to be briefer and of poorer quality than sleep obtained at night.
Medications and Alcohol Affect Sleep
Some medications affect sleep by increasing or decreasing sleepiness.
Alcohol generally increases sleepiness initially but disrupts the REM cycle later in the night, leading to frequent awakenings.
5 Stages of Sleep
Stage 1: Transitional Sleep
Stage 2: Light sleep
Stage 3: A deeper sleep
Stage 4: This is the deepest stage of sleep
Rapid Eye Movement or REM Sleep
Sleep Cycles chart
In a study published in the British Journal Occupational and Environmental Medicine, researchers in Australia and New Zealand report that sleep deprivation can have some of the same hazardous effects as being drunk.
“People who drive after being awake for 17 to 19 hours performed worse than those with a blood alcohol level of .05 percent.”
British Journal article sleep deprivation can have the same effects as being drunk.
In addition, getting less than 6 hours a night can affect coordination, reaction time and judgment, they said, posing “a very serious risk.”
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