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Studies on the effect of voluntary dehydration toward physical performances still inconsistence and needs further study Williams 2005. It is explained that dehydration of
4-8 body weights did not interrupt the physical performances such as intense muscular effort, isomeric muscle strength or endurance. In the other side, it is reported that 4
dehydration has a significant effect towards anaerobic muscular endurance slower to 20- 30 seconds and decreasing 15 knee extension endurance. The dysfunction mechanism
analysis was related to the lost of cilium and the increasing of muscle temperature during sports. It is being stated that no study has shown that dehydration could increase
physical performance. Study on involuntary dehydration show that dehydration less than 2 of body
weight has disturbed physical performances Williams 2005. It is reported that it was related to the cardiovascular function and body temperature adjustment. Dehydration
significantly decrease 4-8 maximal aerobic ability when the total body weight decrease into 3 in the athletes that doing sport in normal temperatures area and the disturbance
getting severe in a high temperatures area. Dehydration also decreases plasma volume which affects the cardiac output and the stream flow of blood through skin and muscles.
The reduction of blood flow through the skin is shown by the decreasing of perspiration and elevation of body temperature. The increasing status of dehydration will increase
body temperature and heart beat and even decrease the amount of the blood that pumped by the heart per beat stroke volume.
2.6 Effects of Dehydration on Mental and Cognitive Performance
The study of Gopinathan et al reflects the effect of dehydration caused by affected
by the differences of weather towards mental performances. Two percents of liquid deficiency can decrease the arithmetic ability, short terms memory and visual focus.
The research about dehydration effects on memories is relatively new Grandjean Grandjean, 2007. The study of Gopinathan
et al. 1988 and Cian et al. 2001 indicate that dehydration which contribute to more than 2 of body weight loss could reduce
cognitive performance. The dehydration occurs because of less water consumption, excessive physical activity, or having high temperature sports. Gopinathan
et al. 1988 study involved 11 healthy adult which having different level of dehydration resulted by the
treatment combination using water intake restriction and high temperature sport activity showed the positive correlation between cognitive disorientation and the severe status of
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dehydration. The subject progressively experienced disorientation on arithmetic ability, short-term memory and vasomotor function when less than 2 of body liquid decreased.
Cian et al. 2001 analyzed 7 healthy people in France by exposing them to heat
and running on treadmill until their body weight loss reached 2.8. Based on that research, dehydration could affect cognitive ability in short and long terms, perceptive
discrimination and subjective estimates of fatigue. Motoric coordination is sensitive to dehydration and could decrease even in mild
dehydration less than 1 of body weigh loss. Sarma et al. 1986 and Cian et al. 2000
showed that when the level of dehydration reached 2 then the cognitive ability in short and long terms, motorist coordination, reaction time, perceptive discrimination
significantly decreased. A further level of dehydration of 3 could also further affect the cognitive ability. Arithmetic ability and the motorist speed showed significant degradation
in the level of 4 of dehydration Gopinathan et al., 1988. Besides that even in the 2
of dehydration, subjects felt exhausted easily Chian et al., 2000.
Medium and severe dehydration determine cognitive function through intracellular, extra cellular and intravascular volume depletion Wilson Morley, 2003. Moreover, the
hormonal and cellular approach is suggested to explain the relationships between dehydration effects towards cognitive performance. It is because the complicated
mechanism of neurobiological which affect cognitive ability. Normally water homeostatic can be managed by our body automatically if there is an imbalance situation that
interrupted the stability of body fluid. In sever accident or in a merge disorientation cases, an excessive respond of homeostatic can induces physiologic disorder. This
condition is described by cellular responds to dehydration in molecular level through intracellular calcium accumulation which trigger nerve inactivation.
Even though study reports still inconclusively stated but there are a tendency that dehydration status could elevate cortisol serum hypercortisolemia. This is relevant with
the hypothesis of cognitive disorientation because medium dehydration can be caused by cortisol hormone. Study in animal assay showed that even though hypercortisolemia
seemed not to affect the passive learning but there were a tendency to reduce active learning ability and short term memory.
Wilson and Morley 2003 explained that the study of cellular network found the possibility of the role of Arginin Vasopressin Perifer AVP into cognitive disorientation
related to dehydration. Study in animal assay, cellular and hystochemical has shown the indication of nitrite oxide NOS as a mediator on managing the body liquid balance
