N.N. Bumarskova, associate professor, Ph.D.
Moscow state university of civil engineering, Moscow

Key words: body fatigue, insomnia, attention concentration, spatial aptitude, reaction time, visual acuity.

Relevance. Water is an element, and many unexpected situations can happen in it, when one is to possess all high-level properties of attention. Otherwise, if the changes of the situation are not seen in time and control actions are not taken, risky mistakes can be made, which can be fatal not only for personal life but for the lives of the whole crew: a wrong maneuver can result in listing of the vessel or ripped sail, broken sail boom or mast, GPS disconnection, going out of navigating lights due to lightning stroke in the mast and so on.

It is known that after 6-8 hours of yachting reaction time increases by 0.1-0.2 seconds. In case of speed increase to over 20 knots the reaction time increases from 1.1 to 1.7 seconds. The increase of reaction time is also noted in case of yachting in the conditions of limited visibility, especially at night, by 0.6-0.7 seconds. This is due to the fact that when the visibility is poor it takes more time to see objects on the water, thus the response latency increases. At night visual acuity is sharply reduced, depth perception gets worse and the field of vision narrows. All this complicates spatial aptitude of a yachtsman. Even when the moon is full visual acuity drops 2 times, while in cloudy weather it reduces 20 times! 

Attention is a special feature of the human psyche, selective orientation of consciousness to perform a specific job. It does not exist without thinking, perception, memory, movement and can be directed to the work of the senses and motor activity. It is assumed that there are three types of attention: involuntary, voluntary and post voluntary. The following properties or parameters of attention are also defined:

1) attention concentration, expressed by the degree of concentration on the object;

2) attention stability characterized by the duration of concentration, the ability not to be distracted for a certain period of time;

3) range of attention characterized by the number of objects perceived at the same time;

4) attention allocation - the ability to perform multiple actions at the same time;

5) switching attention - the ability to change the direction of attention, to switch from one task to another.

Attention is directly dependent on the reaction, and the reaction time may increase under the influence of different factors. As shown by specialized studies, the reaction time of choleric persons turns out to be less than that of the phlegmatic ones by 25-35%, but the number of errors they make is bigger as the choleric are more likely to take hasty and premature actions. In addition, at night the reaction time is also affected by circadian biorhythm. During the long process of evolution man led an active life in day time and slept at night. That is why at night all the vital processes occur at lower levels, slowing down perception, thinking and, therefore, psychomotor reaction time that increases by 75-100% on average.

The reaction time increases with the speed, as when objects move fast perception is complicated and takes place more slowly. Climatic conditions also influence the reaction time as the functions of thinking, attention and memory are disrupted at high temperatures, sensorimotor reactions take more time and are less accurate. Reduction of speed and accuracy of motor reactions at low temperatures is due to the muscles performance deterioration that results in stiffness and malfunctioning of movements.

Measurements carried out in Central Asia have shown that temperature increase of the ambient air to 43ºС increases the reaction time by 30 – 40%.

Sleep deprivation is lack or complete absence of the sleep need reduction that may arise as a result of sleep disorders, a conscious choice or a forced one (e.g., sleep deprivation is also used to treat depression).

After studying the topic, we decided to conduct a study during an expedition in the Aegean and Mediterranean seas in January when the water is rough and therefore maximum attention concentration is required.

The purpose of the study was to arrange a two day long sleep deprivation for the first yacht captain (30 years). In this profession it is the youngest age that is close to that of a student.

Results and discussion. During the expedition the state of the cardiovascular system was monitored (heart rate (HR), blood pressure (BP) and respiratory system (timed expiratory capacity test) data were measured systematically).

Attention parameters were evaluated using the hardware-software complex “Psychotester” and are listed below in Table 1.

Table 1. Captain data during the sleep deprivation for 48 hours, captured by the HSC “Psychotester”

The Figures below show the probability distribution after sleep deprivation during 24 and 48 hours.

After sleep deprivation for 48 hours the HR fall from 72 to 62 bpm was marked in the subject of the study by the end of the experiment.

BP increased slightly: from 119/88 to 139/90 mm Hg.

Genche’s test indicators decreased from 1 minute 18 seconds to 55 seconds at the end of the study.

Conclusions. The data obtained in the study can be due to:

•  an increase in oxygen debt;
•  an increase in sympathetic activation, which increases the metabolic rate;
•  changes in the oxygen or carbon dioxide sensitivity of the respiratory center;
•  changes in metabolism.

A significant decrease in performance was marked along with the prevalence of the central nervous system inhibitory responses (such a state was formed in case of sudden body fatigue). A person working in this state is to be supervised.

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Corresponding author: Pr-azdnik@yandex.ru