Pilot fatigue is a constant threat to all aircrew. There are particular risk factors for those flying high-performance fighter platforms. Flying high-G sorties is physically exhausting. This is an tiring business and even well-rested pilots will find themselves fatigued from the physical and mental demands of combat flight operations. In order for you to effectively combat this deadly adversary, you need to first understand the contributing causes, and then honestly evaluate your own unique habit patterns and risk factors. It is important to be aware of the causes and inevitable effects of fatigue.
CAUSES OF FATIGUE
- Excessive Physical Exertion
- Excessive Mental Exertion
- Inadequate Sleep Quantity
- Poor Sleep Quality
- Circadian Rhythm Disturbance, Working Nights
- Circadian Rhythm Disturbance, Jet Lag
- Medical Conditions
- Medications and/or Supplements
As a modern fighter pilot, your nation requires you to perform flawlessly at the limit of human information processing in a physically demanding environment. Even minor levels of underlying fatigue will manifest at this critical level of human performance. And as fatigue worsens, performance degrades in a progressive and predictable pattern. First, attention declines. Next, one’s ability to reason and reliably evaluate deteriorates. Irritability often follows. Finally, motor skills begin to falter with fine motor skills affected prior to large purposeful movements as daytime sleepiness builds. One famous study cleverly compared progressing levels of sleep deprivation to performance degradation equivalent to increasing blood alcohol content (BAC).
Flight duties and abundant queep equate into very long duty days. Long duty shifts alone are directly associated with fatigue, but these long days have many second-order effects as well. For example, there will likely be an influence on a pilot’s daily sleep habits and diet. Convenient, but unhealthy, snacks become the next best option to a skipped meal due to an extended debrief. Long hours away from home translate into family stressors, which diminish quality and duration of sleep. In addition to long duty hours, circadian rhythm disturbance remains a threat to sufficient amounts of good-quality sleep. Fortunately, this is one cause of fatigue in aircrew that affects the long-haul heavy pilot community much more than the average fighter pilot in a training environment. In the theater of combat, however, all bets are off and the expectation to fly long-duration sorties during times when your body is convinced it should be asleep remains a frequent occurrence. Lastly, any decrease in sleep begins to be banked as a sleep debt, which can create a cycle of fatigue, insufficient sleep, and diminished performance which only worsens over time.
NOBODY IS IMMUNE TO FATIGUE’S DEADLY EFFECTS…NOT EVEN RON BURGANDY:
In the USAF, aircrew do not acquire nearly the hands-on training for fatigue as other human factors, like the altitude chamber for hypoxia or overcoming G-forces in a centrifuge. However, similar to your experience when hypoxic, each individual displays their own constellation of symptoms to fatigue. Most studies of fatigue’s effects in aviators do not demonstrate differences in performance among sub-groups: male and female aviators’ performance are equally affected by fatigue. Good news for ‘Old Ballz’ though – one large study showed that older groups of pilots exhibited generally superior performance when fatigued.
There are a number of helpful strategies that any pilot can employ to combat fatigue. The first step is prevention. Why go to the merge if you can defeat your adversary before entering their threat range? Of course, there will always be times when the merge is unavoidable. A sudden shift in schedule or a poorly planned TDY can provoke circadian rhythm disturbance. A new baby at home or a stressful upgrade may degrade your sleep duration and quality. But effective strategies to minimize the effects of fatigue do exist. The first step is to understand the causes and factors that will place you at higher risk. Honestly evaluate your fatigue ORM. You can be certain that your performance WILL be affected when fatigued.
COMBATING FATIGUE – PREVENTION STRATEGIES
Maintain Your Energy Stores
Much like aircraft energy management is a building block of Basic Fighter Maneuvering (BFM), energy conservation is fundamental to optimal performance by the human machine. Your diet and nutrition is your JP-8. If energy expenditure is greater than the sum of energy inputs and reserves, the body tires more quickly and recovery will be delayed.
Your basal metabolic rate (BMR) is the amount of energy that you require to simply exist. The sum of your BMR and energy required to perform additional activity (to include sitting at a computer doing queep) is your total energy expenditure (TEE) for a 24-hour period. Flying a single-seat jet aircraft is both a cognitively and physically demanding experience. The vibration and noise of the jet, the increased G-forces and necessary AGSM, not to mention the high degree of focused attention, markedly add to the typical fighter pilot’s daily energy requirements.
You would never take a jet that did not accurately report its fuel stores, yet you probably are not always clear of your own energy balance at time of takeoff. Use the below tool to calculate your BMR within a 5% accuracy. This will give you a rough idea of the minimum daily calories you require if you were to engage in NO physical activity.
Powered by BMR Calculator
Nutrition is a complex topic that merits a full, separate post. The body’s primary source of stored energy is from fats. During exercise, carbohydrates in the form of glycogen are utilized prior to fats and provide an immediate energy burst. Glycogen stores are increased thru consumption of carbohydrate-rich foods. Typically glycogen stores expire after 30-90 minutes of continuous exercise, depending on activity and intensity. Proteins are used for many bodily functions, but are preserved from use as an energy source until last resort (i.e. starvation).
When energy output (expenditure) is greater than input (food & supplements), you will lose weight. In the words of former weapons officer, BAT Orzechowski, “It’s science.” But that’s another brief entirely. For the purposes of how to prevent fatigue, you must ensure that you are running an energy surplus, not a deficit.
This slideshow from WebMD contains some simple tips on how to maximize energy through diet. Aside from these energy-rich foods, it is more important to simply maintain adequate energy stores so that you do not hit the wall mid-day, or worse…mid-flight. Eat foods high in complex carbs (70% of your diet) up to 24 hours prior to a demanding flight to ensure glycogen stores are close to maximized. As described above, it is unlikely any sortie would sustain such a high level of exercise for long enough to burn thru all of glycogen stores when fully saturated. Time your meals up to 3 hours prior to takeoff as it will generally take this amount of time for your stomach to empty its contents and allow these nutrients to be available for energy conversion. If you are in need of a faster energy boost, focus on simple sugars generally found in sports drinks and fruit. Hydration is also important as water is a necessary ingredient in the body’s biochemistry to convert glycogen into instant energy. After the sortie, more simple sugars may help you get thru a long complex debrief.
Take Mental Activity Breaks
One fact that may win you a Jeopardy title someday is that the brain makes up only 2% of the body’s total weight, but consumes 20% of its total energy. The food source of the human brain is glucose. Glucose is derived from the breakdown of glycogen (carbs) and fat tissue. Because nerve cells lack the ability to store glucose, the brain is dependent on a constant blood supply rich in sugar to meet its metabolic needs. A supply of oxygen is also required for efficient energy production. This is why when blood flow is cut off to the brain for even several seconds, such as when exposed to high G-forces, one loses consciousness. For a deeper discussion on G-LOC & AGSM, see here.
The body tightly regulates sugar levels in the brain. If you maintain proper nutrition, any chance of sugar levels low enough to affect cognitive function should be negligible. On the other hand, tasks that require high levels of mental workload potentiate any underlying fatigue. This means higher chance for errors and decreased performance. Scheduled activity breaks have been tested in high fidelity flight simulators and demonstrated improved performance following a 7-minute activity break.3 This effect was especially strong during times when the circadian rhythm was at its lowest. Activity breaks may be more effective combined with physical activity. Although a 7-minute mental checkout during a combat sortie would be dangerous, even a minute or two between sets could potentially be helpful. A better suggestion may be to build a short activity break into your timeline between an especially demanding brief and flight operations. Use your time between end-of-brief and time-to-step for an intentional break to relax and gather your mental faculties for the time they will be most required.
Get Adequate Sleep
Duh. But, do you know how many hours are adequate sleep is for you? If you want to find out, next time you are on leave for at least a week, sleep without an alarm clock. Go to sleep when you began to feel sleepy at night. After 3-4 nights of doing so, you should have erased any pre-existing sleep debt. Now, repeat the experiment, noting the time you initiate sleep and the time you naturally awake. The amount of sleep that your body naturally sleeps in the absence of any sleep debt is your sleep requirement. This is normally 7-9 hours. If your sleep volume is outside this range, you’re odd. Once you’ve identified the amount of sleep you need, make it your goal to get this amount of sleep, ESPECIALLY on nights preceding flight operations. Know that if you are getting less than this amount, you WILL suffer from measurable performance deficits. Have available ear plugs or sleep masks when needing to sleep when the rest of the world is awake and active.
Dealing with Sleep Debt
As mentioned above, it is always better to avoid sleep debt by getting a MINIMUM of 7 hours/night. If you know your body requires a higher amount of nightly sleep, that should be your target. Keep a mental log of your nightly hours of sleep. If you begin to develop a cumulative debt, build more sleep into your schedule. The typical person can erase a sleep debt with only 1/3 of the accumulated debt. For example, if you require 8 hours sleep/night and sleep only 6 hours for 3 consecutive nights, you have developed a debt of 6 hours (2 hours x 3 nights). The sooner you get an additional 2 hours of sleep (added to your required nightly 8 hours), the sooner you will be out of the red and performing optimally. If you can’t make this happen throughout the week, use your weekends to erase this debt. Although the utility of banking sleep is often debated, one study showed that after a week of extended sleep periods followed by sleep restriction, performance and alertness improved, while recovery was faster than individuals without ‘banked sleep’ hours.
Get High Quality Sleep
Sleep is divided into Non-Rapid Eye Movement (NREM) sleep and REM sleep. NREM sleep is further divided into 4 progressively deeper stages of sleep. During a typical 8-hour sleep period, these stages progress sequentially in 90 minute cycles. This equates to approximately 4-6 total cycles for a full night’s rest.
It is important that you experience all of the above stages and cycles of sleep. If your ‘sleep architecture’ is distorted, you will likely not feel fully rested upon waking and will suffer similar performance degradation as sleep deprivation. This is not meant to be a brief on sleep hygiene. If you have no idea what I even mean by ‘sleep hygiene’, you can read some of the basic tips offered by the Sleep Foundation. Basically, avoid food/alcohol/caffeine before bedtime and exercise earlier in the day so that your body has a greater need for sleep. Trying to sleep during a circadian rhythm mismatch is more difficult and is covered below.
There are thoughtful, intelligent ways to create a schedule that optimizes performance and minimizes fatigue. Be aware of aircrew who have particularly irregular schedules . Look specifically for those who have recently returned from leave or deployments that are multiple time zones away or those who were recently forced to work on nights. These individuals are high risk for fatigue-based errors and should be scheduled for later showtimes as these are better tolerated when adjusting to new schedules. If operations are to persist for greater than 3 days, it is better to create a dedicated night-shift. These pilots should be identified as early as possible and provided education and time to begin shifting their sleep cycles. If possible, critical duties should be avoided on the first 1-3 nights of duty.
COMBATING FATIGUE – MITIGATING STRATEGIES
Take a Nap
Unlike your bros in the business of long-haul heavy aircraft, cockpit or in-flight bunk napping are not options for the modern fighter pilot. NASA published a study in which short cockpit naps (average nap was 26 minutes) was associated with significant improvements in psychomotor performance and alertness.5 When you have identified underlying fatigue, sleep debt, or sleep deprivation; a short nap before briefs or flight operations may significantly improve performance. A strategic ‘power nap’ can also serve as effective strategies to improve performance when involuntary placed into a circadian disturbance, such as jet lag or working nights. Try not to nap so long that you awake from a deeper stage of sleep in which grogginess can degrade performance for almost an hour. If you do not have significant sleep debt accumulated, keep naps < 45 minutes. This ‘sleep inertia’ is significantly worsened when sleep-deprived.
PILOT ASLEEP AT THE STICK PRANK. TRY IT NEXT TIME TAKING MOM OUT ON THE CESSNA:
Dealing with Shift Work Disturbances
Maintenance of human homeostasis is based on a circadian rhythm with internal and external means of regulation. It is generally agreed upon that our clock operates on a 24-25 hour cycle. Between the hours of 21:00 and 06:00, core body temperatures and plasma cortisol decrease, plasma melatonin levels increase, and subsequently alertness remains at its natural low level. Most people’s circadian rhythms reach a low between 02:00 – 05:00. A second, but not quite as extreme, nadir is experienced between 2 – 5 pm (The 2-5 rule). The nadir usually correlates with the lowest core temperature experienced by the body. It shouldn’t be surprising that most safety-intensive industries see peaks in mishaps during these ‘low’ time periods.
Working on ‘the back of the clock’ will confer a certain level of performance degradation that is unavoidable. Be aware of this and build this fact into your ORM. Again, smart scheduling can make these transitions less painful. When you have the time to prepare for a radical change in schedule, begin to slowly shift yourself several days in advance. A well-timed power nap early in the shifting period is advisable and preferable to decreased alertness, progressive performance deficits, and micro-sleeps. Chemical and pharmacologic (drugs) strategies also have their place and are described below.
Dealing with Jet Lag
Again, begin preparing for approaching trips as early as possible. The earlier you can begin to shift your circadian rhythm and sleep patterns, the sooner you will recover from jet lag. Change your watch to your destination time days in advance and begin to shift your wake-sleep cycle as early as practical. Upon arrival at your new location, a power nap prior to flight missions may significantly increase alertness. Seek daylight during waketime hours as this will prompt your body’s clock to begin shifting sooner. Also, keep in mind the general rules of jet lag so you can more accurately evaluate your risk for performance deficits:
• Total westbound travel recovery time is about 1 day per time zone crossed
• Total eastbound travel recovery time is about 1.5 days per time zone crossed6
It is well documented that physical activity in many animal species will promote changes in the biological clock. Current medical research, however, does not provide a clear answer to exercise’s effect on humans. Regardless, since exercise poses little health risk and the benefits for cardiovascular health are clear, I recommend using exercise as a tool to possibly assist with clock changes. If shifting from days to nights, schedule yourself time to exercise during the night when you would normally sleep the weekend prior to shift change, then continue doing so while working nights. If preparing for a jet lag mismatch, begin exercising during local time sleep periods and destination time wake periods. Continue this pattern upon arrival to possibly hasten resynchronization. There is not good evidence to support one exercise type or duration over another. I recommend subscribing to any exercise regiment that you enjoy, and will actually do. Light exposure can be used similarly.
The USAF will not let you fly for 48 hours after travel crossing 4 time zones. In most cases, however, this 48 hour period is not sufficient for full recovery. Just knowing this will be helpful. If you are having difficulty attaining sleep during the new local nighttime or remaining alert during local daytime, chemical and pharmacologic assistance may prove helpful. See below.
Use Caffeine as a Countermeasure
Caffeine is a valuable weapon to combat fatigue, increase alertness, and improve performance. But, it has its limitations. Caffeine takes about 30 minutes to achieve peak values in the bloodstream and take maximum effect. The benefits of caffeine will last for 4-5 hours in a typical person. Recommended dose is 100-200 mg every 5 hours. Maximum daily dose recommendations vary from 500-1000 mg in a 24-hour period. Below are a few common sources of caffeine with associated caffeine contents:
• Cup of Coffee: 100-150 mg caffeine
• Cup of Tea: 25-75 mg caffeine
• Can of Red Bull: 80 mg caffeine
• Can of Mountain Dew: 55 mg caffeine
• 5-Hour Energy: 215 mg caffeine
• Monster Energy: 92 mg caffeine
• Hershey’s Special Dark (1bar): 31 mg caffeine
I recommend getting your caffeine thru pure sources such as coffee, tea or dark chocolate. Many of the energy drinks currently on the market have other ingredients that are not regulated. Although the recent allegations of deaths linked to these drinks may be dubious, I wouldn’t chance it until the FDA provides a more clear answer.
Don’t get yourself into a cycle of using caffeine as a way of masking sleep deprivation. There is no substitute for good sleep. Instead, use caffeine to promote alertness during circadian nadirs (02:00-05:00 & 2 pm- 5pm), times of wakefulness when jet-lagged, and other times when the consequences of fatigue are dire. Less frequent use of caffeine will ensure that when it is utilized, your body is less adapted and the overall effects will be greater.
Some people are highly sensitive to caffeine and will feel uncomfortable restlessness or even a racing heart after ingestion. If you find yourself reacting to caffeine in this way, it is best not to use to counter fatigue. Caffeine can also worsen indigestion and reflux. Many people claim that caffeine will dehydrate you based on its effects as a mild diuretic. Recent studies demonstrate that this effect is very small, and only seems to be in those who do not use caffeine on a regular basis. Those of us who drink coffee daily do not have to worry about the diuretic effects. Lastly, frequent users of this substance will experience withdrawal symptoms in some cases causing headaches that can last up to a week.
Get Meds from your Flight Surgeon
If you are still reading this post, its likely only because to get to this part. First, regardless of what you think, a flight surgeon is more than just a Go/No-Go pill vending machine.
The use of Go and No-Go pills by military personnel is undoubtedly an effective means of managing fatigue in the complex combat environment. Unfortunately, the DoD policy is complicated by a constant struggle between many forces- mission effectiveness, aircrew safety, pharmacologic regulation, and media scrutiny. This topic is large enough to merit its own separate post and discussion. To summarize, these medications have been used for decades and their effectiveness and safety record is well documented in both controlled scientific and real-world operational environments.
Other Herbals such as Melatonin, L-tryptophan (the often accused agent for post-turkey thanksgiving naps), Kava Kava, and Tyrosine are all natural herbals marketed as sleep aids. These remedies’ effectiveness is questionable and they are not currently approved for use by DoD aircrew.
- Be aware of your current level of fatigue and risk for error. Sleep deprivation, sleep debt, and operating during circadian rhythm lows are all risk factors. The 2-5 rule is a good way to remember that between 2-5 am and 2-5 pm are circadian lows.
- Know your approximate basal metabolic rate (BMR) and total energy expenditure (TEE). Ensure that your daily caloric intake at least meets your estimated TEE. You would never want to hit the wall mid-flight.
- Focus on a carbohydrate-rich diet 24 hours prior to a demanding flight to fill glycogen stores. Complex carbs from starchy foods (pasta, rice, grains) are recommended unless you need an immediate boost just prior to flight. In this case, simple sugars (juice, sports drink, fruit) are preferred.
- Maintain adequate hydration. Water is a necessary ingredient in the chemical process of energy creation.
- Take short, intentional activity breaks in response to feelings of task saturation. Although difficult and possibly dangerous in the jet, during non-tactical phases of flight even a few seconds to minutes of time designated for mental recovery may help with excessive mental exertion. Build a 5-10 minute break into your timeline between demanding briefs and sorties. Using this time to relax or engage in physical activity has proven benefit.
- Make it a priority to always get 8 hours of sleep per night. Avoid getting any less than 7 hours, especially on nights preceding flight operations. If sleep deprived, you WILL commit more errors and suffer measurable performance deficits.
- Practice good sleep hygiene. Develop habits that lend to consistent high-quality sleep.
- Fatigue and sleep disruption need to be a consideration when designing flight operation schedules. This is especially true when planning ops with abrupt changes from normal day shifts to night shifts. Scheduling ahead for operations in distant time zones can be done in way which will hasten shifting of biologic clocks. Consult your flight surgeon for further assistance!
- Keep a mental or written tally of your sleep over the past several nights. Be aware of sleep debt. Performance will progressively worsen with consecutive nights of insufficient sleep. Most people can erase sleep debt with an additional 1/3 of the total debt + their nightly requirement.
- Take a strategic ‘power nap’ before briefs or flight operations if experiencing daytime sleepiness. Keep naps to less than 45 minutes (NASA study = 26 min) to prevent excessive post-siesta grogginess.
- When changing from day to night shifts or crossing more than 4 time zones, begin shifting your circadian clock naturally as early as possible.
- o Take a power nap early in your shift or upon arrival at new destination.
o Set your watch to the destination local time days before arrival. Sleep during destination night time and stay awake during destination waking hours if practical.
o Upon arrival to destination, ensure that you have adequate exposure to sunlight during wake time hours. You can also use exposure to bright lights during destination wake hours days prior to departure. These actions will promote early circadian clock shift.
o Similar to light, exercise may assist in shifting humans’ circadian clocks. If possible begin exercising at the new shift/destination wake time several days before the shift/travel. Continue this pattern after new shift/arrival.
- Caffeine is effective in combating fatigue and improving performance. Caffeine generally takes 15-30 minutes for max effect and lasts 4-5 hours. Recommended dose is 100-200 mg every 5 hours (1-2 cups of coffee). Avoid getting caffeine from energy drinks that have many additional unregulated supplements as their safety is currently in question.
- Go & No-Go Pills have been used for decades and their effectiveness and safety record has been well documented in both medical studies and the operational environment. Unfortunately, current policy is mired in a struggle of opposing forces and programs and their use remains highly regulated. There is no substitute for good sleep. Chemical sleep aids should only be used as a backup or when completely necessary.
- Melatonin, L-tryptophan, Kava Kava, and Tyrosine are natural herbals marketed as sleep aids. Their effectiveness is questionable and they are not currently approved for use by DoD aircrew
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2.John A. Caldwell, J. Lynn Caldwell. Female and Male Aviators are Not Affected Differently by Sleep Deprivation and Continuous Task Demands. U.S. Army Aeromedical Research Laboratory, 1996.
3. Neri DF1, Oyung RL, Colletti LM, Mallis MM, Tam PY, Dinges DF. Controlled breaks as a fatigue countermeasure on the flight deck. Aviat Space Environ Med. 2002 Jul;73(7):654-64.
4. Rupp TL1, Wesensten NJ, Bliese PD, Balkin TJ. Banking sleep: realization of benefits during subsequent sleep restriction and recovery. Sleep. 2009 Mar;32(3):311-21.
5. Rosekind, M.R., Graeber, R.C., Dinges, D.F., Connell, L.J., Rountree, M.S, Spinweber, C.L.,& Gillen, K.A. (1994). Crew factors in flight operations IX: Effects of planned cockpit rest on crew performance and alertness in long-haul operations. Moffett Field, CA, NASA Ames Research Center, 1-82.
6. Ferrer CF Jr1, Bisson RU, French J. Circadian rhythm desynchronosis in military deployments: a review of current strategies. Aviat Space Environ Med. 1995 Jun;66(6):571-8.