Explorers

Marine Watch Site Map

TECHNICAL LIBRARY

Decision Making

CREW FITNESS

DECISION MAKING

Poor decisions cause injuries and deaths on land,sea and in the air. Factors contributing to poor or wrong decisions can be simple or complex and behavioural analysts have issued reams of material to help us understand the processes involved in attempts to reduce the number of times humans make errors. The most common and recurring causes revolve around fatigue brought on by a variety of circumstances. We probably all know too well how a failure to concentrate properly on the task in hand can lead to a mishap or a near miss - driving a vehicle is the most common arena for most people and this is an activity where things can go wrong very quickly. Equally spectacular is the aviation world where the results of poor decision making or concentration can often be quite catastrophic and spectacular. In the boating world, the pace of events can be deceptively slow but nevertheless unnecessarily dangerous when there is a critical lack of concentration or a poor decision made at a critical time. An understanding an willingness to try and avoid the dangers are necessary ingredients to safe boating.
The factors set out below are worthy of perusal. Even though they are relevant to almost any human task some are more applicable to the relatively long term situations.

FATIGUE

Fitness Topics

     Fatigue being extreme tiredness can be a dangerous condition simply because it can be unrecognised by the victim. Even when recognised fatigue can be a major problem in a crew because of the difficulty in getting adequate sleep - the only recognised antidote. Humans need 7-8 hours sleep each night and failure to get enough builds up a sleep debt which must be repaid. There is no way that a sleep credit can be built up in advance of an onerous task.
     There are four stages of sleep ranging from light to deep in stage four - the stage where fatigue is beaten. In a normal sleep cycle most of the stage four sleep occurs early in the first third of the cycle. Fatigue reduces performance. Decision making is impaired, attention and concentration is less than optimal and crew are prepared to accept a lower standard of performance than they would normally. Reducing sleep by just one hour leads to increased daytime drowsiness which is cumulative. A loss of two hours sleep leads to impaired alertness and measurable reduced performance.
      Alcohol is used as an aid to sleep but although it can reduce the time taken to fall asleep it interferes with the normal sleep patterns. It also increases the level of subsequent daytime sleepiness. Alcohol also adversely affects the kidneys and increases urine production - thus increasing the risk of dehydration.
     Caffeine stimulates the central nervous system and can improve alertness. It takes time to work and too much will be detrimental.
      Sleep Inertia is the transition phase between sleep and wakefulness.It interferes with task performance - including decision making. The degree depends on the stage of sleep that was interrupted and it can last for up to 30 minutes. This has implications for the change of watches. For more detail see the general item on Sleep & Fatigue.
      On a lengthy boat trip (24 hours or more) the issue of fatigue is a big one. On shorter trips fatigue can also loom large if the crew start out in an already fatigued state. This is all too common on a day fishing trip where the crew have had a "good night" before the trip and have only had a few hours sleep. Skippers need to be alert to signs of fatigue in all on board - including themselves. These include drowsiness, slow reactions, irritableness and unusual behaviour.

STRESS

Fitness Topics

Stress places excessive demands on a person and may exceed the person's ability to cope. Stress can cause physical symptoms - insomnia, poor appetite, headache and irritability. The body's response to stress produces physiological effects - muscle tremors, high heart rate, sweating & lack of coordination There are three sources of stress - environmental, life, reactive and organisational.

Life Stressors are emotional, domestic, social & financial worries. They can create problems among a boat crew especially bearing in mind the close confines on most boats where there is little or no private space. These stressors ar usually given a score according to the average level of stress they induce - a score of 60-80 being a normal level in our society. A score of over 100 represents serious stress. The death of a spouse rates 100 points while going on holiday rates 13 points.

Environmental Stressors include excessive noise, vibration, abnormal temperatures (>30 & < 25 deg C) and humidity (>60% & <40%)

Reactive Stress is the mental and physical reaction to certain abnormal situations - such as a near collision, encountering a rogue wave or blowing out a sail.

Organisational Stressors are caused by the conditions on the boat - especially the standard of the boat and the crew interaction and the capability and skill of the skipper.

Stressors are cumulative and additive and everyone has their own personal limit. If the limit is exceeded even a moderate workload can be hard to carry out and the subject is in stress overload with performance and decision making becoming degraded. Management involves recognition and removal or minimisation of stressors. In this process prioritisation of tasks is critical and the compliance with agreed procedures or practices is needed. Proper task delegation will help in reducing workloads. Individual techniques should be practiced - keeping fit, having proper rest breaks, using relaxation techniques & knowing personal capabilities and limitations.
For related information see the item on Watchkeeping

DEHYDRATION

Fitness Topics

     In Australia dehydration can be a big risk. For the mariner there will not be a problem stemming from low humidity; however there is still a risk of dehydration and its effects.
     Under normal circumstances an adult needs about 1.5 litres of appropriate fluid per day. In a 24 hour period an adult loses 500 ml in perspiration, 500 ml through urine and another 500 ml through the respiratory system. This fluid loss would occur even when completely at rest sitting down. With exertion or in hot conditions the fluid loss is greater so that more that 1.5 L will need to be consumed to maintain a proper body fluid level.For most recreational mariners who have long exposure to the sun dehydration becomes a real risk.
      Dehydration reduces performance, impairs judgment and decision making. In the long term it can increase the risk of developing kidney stones and might increase the chance of heart disorders In the short term dehydration can lead to heat exhaustion or heatstroke.
      Heat exhaustion causes nausea, vomiting, dizziness, fainting, excessive sweating and a slight rise in body temperature. Heat stroke is the failure of the body to regulate temperature and the body temperature rises to dangerous levels. The nervous system malfunctions, muscles can break down and kidney damage can occur.
     Thirst indicated a fluid loss of about 3% of body weight. Symptoms of weariness, nausea and emotional instability indicate a fluid loss of around 5% of body weight. At 10% loss the symptoms include a swollen tongue and delirium with attendant circulatory problems, concentrated blood and kidney problems. The limit of human survival is reached at 20% fluid loss.
     Dehydration is insidious and the individual may not realise that they are dehydrated. Thirst is not a reliable indicator. However urine is. Urine should be straw yellow in colour in adequate amounts. Dark urine is concentrated - suggesting that the body is attempting to conserve as much fluid as possible. In such a case drink enough to return the urine to the lighter colour.
    Avoid or minimise alcohol, coffee, tea, soft drinks because these affect the kidneys increasing urine production and exacerbating dehydration. Plain water is the best replacement fluid - keep it handy and drink regularly and often.

HYPOGLYCAEMIA

Hypoglycaemia is a condition caused by low levels of blood sugar in the body. It can cause weakness, tremors, dizziness, sweating. muddled thinking, slow reactions, uncharacteristic behaviour, lethargy and even unconsciousness. Eating proper food will cure this condition but it could take up to 30 minutes after blood sugar levels have recovered for symptoms to disappear. To avoid hypoglycaemia eat properly - at least every 6 hours during periods of wakefulness.

SEASICKNESS

In the context of crew fitness seasickness is a potentially dangerous condition - especially on a prolonged voyage. There have been recorded cases of rescues at sea to save a sailor suffering from seasickness. Seasickness can range from a mild loss of appetite and a feeling of lethargy to a severe case where neither food or liquids can be retained.
Strategies to combat seasickness are many and varied. In its basic state seasickness is a form of motion sickness so that once at sea there is little to be done to combat the motion - except to try and stay as close as possible to the centre of the craft where the pitching and rolling motion is least. Avoid breathing foul air (engine made fumes) and keep in the fresh air. For some, lying down with the feet raised to at least the heart level is beneficial. There is also a range of combatative pills that work for others - but most of these have side affects and should not be taken with alcohol. A simple fix which works for many people is to consume food and/or drink containing ginger - biscuits, sweets or soft drink have all been known to be effective. For those prone to seasickness experiment to find a remedy best suited to the individual. Most successful remedies need to be put in place in advance - it can be too late once the seasickness starts. Sometimes severe apprehension will cause symptoms similar to seasickness. Seasickness does not necessarily stop a person from performing their watchkeeping tasks - however all cases of seasickness, no matter how mild, should be reported to the skipper to allow monitoring of the situation so that crew adjustments can be made if it becomes necessary.

ADEQUATE SLEEP & REST

REGULAR FLUID INTAKE
(WATER BEST)

FOR A FIT AND HEALTHY CREW

ADEQUATE FOOD

BE ALERT FOR DANGER SIGNS

REDUCE & MINIMISE STRESS

AVOID DEHYDRATION
(MINIMISE SUN EXPOSURE)

Fitness Topics

Library Catalogue

Marine Watch Site Map