Importance of hydration in physical exercises (Part 1)

Physiological consequences of physical exercises

Burning of energy

When you physically exercise, your muscles will either relax or contract. However, not all muscles will contract at the same time, and not all muscles will relax at the same time. At certain point in time, some muscles will contract, and some will relax. The net result of this is the generation of movement, which could be in the form of breathing, running, walking, dancing, and many more. As the muscles contract and relax, there is burning of energy which is ultimately derived from the foods that you take. Without the foods that you take, the muscles could not efficiently work. Thus, when you exercise without previously taking your meal, you will feel weak and could not continue doing your workout.

Production of heat

When the energy is burned—and the burning is quite fast in physical exercises—there is heat production, as one form of energy is transformed into another. This biological event increases your body temperature.


When your body temperature rises, there must be a biological mechanism of lowering it. Otherwise, your body will suffer from overheating, otherwise known as heat stroke. Hence, your body sweats; the more intense your exercise is, the more sweat your body will produce. As the water flows out from your sweat glands located beneath your skin, your body temperature goes down.

Water loss

When you sweat, water and some electrolytes, such as sodium, are lost from your body. If you do not replenish the lost water, you will suffer from a number of consequences.

Consequences of severe water loss


When water loss from severe sweating is so significant, you will suffer from dehydration if you will not have adequate hydration as you physically exercise. There are three gradations of dehydration. These are mild, moderate, and severe dehydration. Whichever the case is, you will need to take adequate water so that one gradation will not progress to a worse situation. If you have reached the stage of severe dehydration, and yet you do not have adequate water replacement, you may die from the so-called hypovolemic shock.

Hypovolemic shock

One of the vital signs of your body is yourblood pressure (BP). It has two figures written in a fraction form. The upper number, or numerator, represents the systolic blood pressure, and the lower number, or the denominator, represents the diastolic blood pressure. The normal systolic pressure ranges from 90 to 140 mm Hg, while the normal diastolic blood pressure is 60 to 90 mm Hg. When your blood pressure is lower than 90/60, you have low blood pressure; when your blood pressure is higher than 140/90, you have high blood pressure.

There are two determinants of your blood pressure. These are the cardiac output (CO) and the peripheral resistance (PR). Thus,

Equation 1: BP = CO x PR.

In turn, your CO equals the product of the stroke volume times your heart rate and the PR is the determined by your intravascular volume and the diameter of your blood vessels. If we summarize the relationships of the different variables, we have this equation:

Equation 2:BP = {Stroke volume x heart rate} {Intravascular volume/diameter of your blood vessels}

Based on Equation 2, even if we hold all the other variables as constants, and only the intravascular volume changes, you can conclude that the blood pressure changes. When you lose too much water from any form of physical exercises, the intravascular volume decreases, and your blood pressure drops. When the water loss is too much, your intravascular volume decreases severely and your blood pressure will drop significantly, leading to hypovolemic shock and then death.

(To be continued)

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