Question

Loss of what minimum percent of a person’s body weight of water can lead to detrimental effects such as decreased ability to maintain core temperature, especially during exercise?

Answer 1

Answer: A dehydation of 5% body weight in normal temparature.

Human body consists of 45%-75% of water. That is we have an average of 60% water present in intracellular form and extracellular( blood). The reduction of water causes serious issues to our body.
Thermoregulation, where our core body temperature is maintained in a constant level is done by water.The core temparature can be affected by exercising. It causes the water to form as sweat inorder to reduce heat. This causes dehydration.
Even 1% reduce in bodyweight due to water loss can affect the circulatory and thermoregulatory syatem.

The ciculatory system, consisting of blood having 90% water, in time of dehydration causes decreased rate of blood flow. It also causes imbalance in pottasium and sodium. The heart rate thus increases unhealthly. Also the core body temparature increases because it affects the sensitivity of sweating mechanism.

The % of dehydration level which causes the core temparature fluctuation depends on the external temparature also. Normally a 2% water loss causes mild dizziness and tiredness. 5% loss causes thermoregulation and physical activities.

A 5% loss of water can reduce the perfomance of a person by about 30%. When doing a high intensity exercise, even a 2.5% water loss can cause 45% loss of capacity. A 5% dehydration causes a rise of temparature upto 39℃. It also causes glycogen breakdown excessively.