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How tired are you, really???

The worst person to is the person that you are worried about!

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Increased reaction time• Timing errors in response sequences• Less smooth control

Reduced attention • Preoccupation with single tasks or elements• Reduced audiovisual scan

Diminished memory • Forget peripheral tasks• Revert to “old” habit patterns

Withdrawn mood • Less likely to converse• Less likely to perform low-demand tasks

Effects of Fatigue on Performance

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We have an intrinsic biological clock with a cycle of roughly 24-25 hours.

Many bodily functions cycle about these daily circadian rhythmsa) Blood Pressureb) Heart Ratec) Core Body Temperatured) Others...

Perhaps most important is that performance also cycles about normal circadian rhythms.

Given the typical circadian cycle, performance peaks between 1200 and 2100 hours and falls to a minimum circadian trough between 0300 and 0600 hours.

Circadian Rhythms

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Circadian Rhythms

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While the body clock is inherently capable of monitoring the passage of time, it differs from most clocks in that it is flexible and must be set, or synchronized, before it can accurately predict the timing of events.

Entrained by external synchronizers, Zeitgebersa) Sunrise-Sunsetb) Ambient Temperaturec) Mealsd) Social Cues

Circadian Rhythms

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• Deficits in performance, mood, motivation, and behavior

• Sleep disturbances

• Lassitude, anxiety, irritability, depression

• Slow reaction times, defective memory for recent events, errors in computations, and a tendency to accept lower standards of performance.

Circadian Desynchronization“Jet Lag”

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Circadian Desynchronization“Jet Lag”

• Rapidly traveling from one time zone to another, the body clock and rhythms it controls must resynchronize to the local geophysical and social zeitgebers.

• Eastward travel shortens the day.

• Westward travel lengthens the day.

• Resynchronization occurs much more rapidly when traveling west

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Circadian DesynchronizationCountermeasures

Non-Pharmacological Countermeasures

- Ramping and the USMC

- Resynchronizing tips

Pharmacological Countermeasures

- Melatonin

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Our sleep/wake cycle is closely tied to our circadian body temperature

a) Cave studies

Sleep

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Circadian Rhythms

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Stages of Sleep

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Circadian Rhythms

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Our sleep/wake cycle is closely tied to our circadian body temperature

• Cave studies

The duration and “quality” of sleep is dependent upon body temperature

• People sleep longer and report a better night’s sleep when they retire near the temperature trough.

It is the timing of sleep, not necessarily the amount of sleep, that is most significant.

Sleep

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• The circadian rhythm of sleepiness (MSLT) is remarkably similar to the circadian rhythm of body temperature.

• There are essentially two times when your body is prepared to sleep.

1) The most obvious is between 2200-0600

2) Post-prandial dip

When is the Best Time to Sleep?

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How Much Sleep Do You Really Need?

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Effect on Complex Mental Operations

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How Much Sleep Do You Really Need?

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How Much Sleep Do You Really Need?

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How Much Sleep Do You Really Need?

• Sleep requirements vary among individuals.

• A minimum of 5 hours of uninterrupted “core” sleep during the circadian trough is necessary to maintain performance in the lab.

• Sleeping in excess of 10 hours may produce sleep drunkenness.

• When physical and mental workload exceed normal limits, the minimum amount of sleep needed to sustain performance is more.

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Napping

• When sleep is not available or shortened by operational concerns, combat naps are a viable alternative.

• Even naps as short as 10 min are restorative in nature

• Long naps (typically greater than 1 h) may leave the individual feeling more tired than before napping (Sleep Inertia)

a) Sleep inertia may last 5-20 min upon awakening

• Practice Napping

Napping

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Countermeasures to Fatigue

Pharmacological

a) Caffeine

b) Meth-amphetamine

c) Amphetamine

d) Methylphenidate

Non-Pharmacological

a) Tyrosine

Non-Pharmacological

a) Tyrosine

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Countermeasures to Insomnia

Pharmacological

a) Barbiturates

b) Benzodiazepines

c) Alcohol

d) Antihistamines

Non-Pharmacological

a) Keep a routine

b) Vigorous exercise

b) Warm baths

c) Tryptophan

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Sweet Dreams