In the Figure above: X = sleep in prior 24 hours Y = sleep in the prior 48 hours Z = time since your last sleep (i.e. from when you woke up, until now). As a broad guide, from scientific evidence, we can say that if: X is less than 5 hours; Y is less than 12 hours; or Z is greater than the sleep obtained in the prior 48 hours; you are likely to be experiencing some form of fatigue-related impairment and therefore need to carefully consider your risk exposure.

Volume 49, No. 4, March 23, 2006

Today’s varying operational and personnel tempo pushes the need for fewer people performing at high levels of efficiency.

There exists ample documentation (including an entire chapter in the soon to be released ABR 6303 Version 4) on the detrimental effects of fatigue on decision-making and judgement. Without understanding fatigue and effective fatigue management strategies, we not only increase the risk of fatal mishaps but we require more people and more effort to get the job done.

In addition to managing fatigue, it is also important to educate personnel about self-management strategies for fatigue risk management.

Fatigue is the state of feeling tired, weary or sleepy that results from prolonged periods awake, loss of normal sleep, mental or physical work, extended periods of anxiety, and exposure to harsh environments.

This is a separate type of tiredness from repetitiveness; this is a lack of sleep. Generally fatigue causes deterioration in mood, decreased power of judgement and reasoning, and slow and inaccurate performance.

Think of a debit card with an absolute limit (sleep), you can only spend and repay sleep. You can NOT bank or ‘save up’ sleep. Short-term physiological or acute fatigue can be restored only by restorative sleep; however, because of the body’s natural sleep/awake rhythm there are times when you won’t be able to ‘top up’ your card. Of course, everyone is different and that includes the limit on your sleep debit card, but the general ratio is two hours awake to one hour asleep.

Most people are aware of the effects of alcohol on performance. Similar effects apply to fatigue.
For many years, fatigue was discounted as a potential cause or contributor to human error. One reason for this misunderstanding was the old myth that fatigue could be prevented by various characteristics: personality, skills, motivation, physical strength or professionalism.

However, more recent accident data and research, including our own OHSIR system, point to fatigue as a cause of and/or contributor to human error precisely because of its impact on performance. Human error resulting from fatigue is now widely recognised as the cause of numerous maritime casualties, including one of the worst maritime environmental disasters in the last century, the grounding of the Exxon Valdez.

We have all heard from the media how truck drivers reach fatigue levels at which efforts to prolong alertness fail and spontaneous micro-sleeps occur with disastrous results. Research concluded that operators themselves are often poor judges of fatigue levels, and that decisions of duty duration should be made at the task planning stage. The U.S. Army is starting to plan sleep like any other logistic resource.

Locally, it has been estimated that 10 to 25 percent of accidents in the Great Barrier Reef are fatigue related, largely stemming from a lowered level of vigilance leading to a lack of position monitoring, incorrect reading of navigation equipment and pilots failing to check a ship’s position at critical times or to communicate information to the crew.

Responsibility

Non-work-related fatigue is increasing due to modern lifestyle factors, such as a 24-hour society, social pressures, the Internet and international televised sport.

This places an increased onus and personal responsibility on the individual to manage fatigue arising from both work and non-work activities; however, it is the role of supervisors and Commanders to monitor all aspects of fatigue; to minimise fatigue where ever possible, and to mitigate the effects of fatigue where it is unavoidable.

Primarily, this involves ensuring that individuals are provided with sufficient sleep opportunity in between work periods. This is likely to include monitoring the effects of watchkeeping, ancillary duties, use of short leave and assessment of task importance and fatigue levels.

It is the responsibility of the individual to undertake their normal daily work routine in a fit state. Achieving a fit state for work may be compromised by certain conditions including, but not limited to, a lack of sleep or being under the influence of alcohol.

Individuals are advised to avoid behavioural practices such as not sleeping when the opportunity is presented. These practices may place the sailor and/or their shipmates at risk. Every individual is expected to be aware of their fatigue level.

Put simply, work and play must be balanced with sleep.

Mitigating Fatigue

To recover your fatigue debt, you must realise that the longer the sleep, the more restorative it will be, up to the limit of your ‘debit card’. That is, a six-hour sleep period will be far more restorative than three sleeps of two hour duration. The longer an individual is deprived of sleep, or the larger the sleep debt, the longer the individual takes to recover.

National Aeronautics and Space Administration (NASA) researchers concluded that, ‘regardless of training, professionalism, or having the ‘right stuff’, extreme sleepiness can precipitate uncontrolled and spontaneous sleep’. You cannot escape sleep, no matter what you do, sleep always comes because sleep is integral with being awake.
Napping is useful for extending alertness.

However, a nap will never replace lost sleep. It can only be used to supplement longer sleep periods. Researchers have found that short naps lasting 45 minutes or less have positive effects in prolonging alertness and are a powerful tool for reducing the chance of dangerous uncontrolled micro-sleeps.

Even 15-minute naps have been found to be beneficial. While there are definite benefits to napping, individuals need to be aware that after the nap, they may wake slowly due to sleep inertia (ie: ‘groggy’). So grab a nap when you can!

In addition to sleep opportunity, there are several personal factors that can impact upon sleep quantity and/or quality. Some of these factors include diet, exercise and hygiene. In addition, different people need different amounts of sleep.

Minimum Sleep Requirements

It is often difficult to detect our level of impairment due to fatigue. Experience with alcohol impairment would say that if a typical male consumes two alcoholic beverages in the first hour of drinking and one every hour after that, they would be unlikely to exceed a blood alcohol concentration in excess of 0.05%.

Through analysis of the scientific literature, we can provide similar ‘rules of thumb’ to detect fatigue-related impairment (Figure).
All members of Navy must take positive steps to achieve responsible management of fatigue.

More than any other safety-related aspect of Navy work, both the potential and residual risk presented by fatigue can at times be the most present yet least measurable.

Potential fatigue risk can be identified within the context of the operations or activity being planned. Within this context, command may tailor the level of risk it is prepared and able to tolerate through sensible mitigation and controls.

The mutual responsibility of both command and Naval personnel in achieving effective fatigue management in this non-prescriptive approach is essential to achieving the aim to KEEP NAVY SAFE, and to of reduce risk to ALARP.

.