Fluids And Fitness

Body fluid level is an important component of keeping it in top condition for best performance. The relationship between fluids and fitness is a close one, as the fluid lost to sweat must be restored for optimum health.

As a person exercises, the internal body temperature rises. That triggers the body to release internal fluid to the outside through millions of sweat glands and via heightened respiration. As the high temperature sweat evaporates off the skin, it takes heat with it, cooling the body down again.

That internal temperature regulatory system is vital to health, but losing too much fluid can also produce problems. High activity can cause a person to lose three quarts or more of fluid per hour. As the amount of fluid lost increases, performance decreases.

Excessive fluid loss strains the cardiovascular system as well, which can lead to dizziness, muscle cramps and even heat stroke, in extreme cases.

Professional guidelines recommend regular replacement of both water and electrolytes (sodium, potassium and others) by drinking a sports drink before, during and after a workout. The right amount will vary with body weight and type, tendency to sweat, external temperature and other variables, but here are some rough figures.

Drink about 18oz (0.53 liter) a couple of hours before beginning your workout, then another 10oz (0.3 liter) about 15 minutes before starting your warm-up. Drink at least 30oz (0.89 liter) every hour you work out, then - after a cool-down period of a few minutes - another 20oz (0.59 liter) after the workout.

Caffeine-containing drinks should be avoided when re-hydrating since they have a diuretic effect. Consuming alcohol, too, is a bad idea for at least a couple of hours after a strenuous workout. Apart from the high amount of calories most alcoholic drinks contain, the alcohol can disrupt the smooth rate of cool-down as the body temperature changes.

Beware of sports drinks that have high amounts of sugar. You don't want to put back all those calories you worked hard to burn, and too much sugar can unbalance cardiovascular regulation after vigorous exercise. That means, go easy on both soft drinks and concentrated fruit juices. Even diet soft drinks have excessive carbon dioxide, which is less than ideal for best recovery.

Look for drinks that replace magnesium (~100 mg per liter), as well as sodium and potassium. Both sodium and potassium are essential elements for proper heart function. They help regulate cellular electrical activity.

Isotonic drinks are designed to closely match the body's natural concentrations of needed minerals, vitamins and enzymes. That makes them easier to absorb and excellent replacement fluids.

Maintain overall health, avoid medical problems and maintain peak performance by proper fluid regulation.

What Good Is Sweat?

Perspiration isn't generally considered desirable. It makes clothes wet and uncomfortable, it makes our skin unpleasant to touch and it often smells bad. But the biological fact is that sweating is essential to good health, especially during exercise.

Why?

Humans take in and use water for a number of important physiological functions. It provides a medium for cells and tissues. It makes possible the transport throughout the body of important elements or compounds like sodium and sugar not to mention forming part of the blood that moves them. It provides structural cohesion and lubrication between all parts. But there's one more highly important function it helps perform: temperature control.

Homeostasis is the body's ability to keep certain processes and factors in equilibrium, this is not too far from a central point. Body temperature is one key item among those. When body temperature gets too high, we experience fever and ultimately heat stroke. If it's too low, we get chills. Both are signs that the body is in a less than ideal state.

One major reason is that all chemical reactions within the body have to take place within a very narrow range in terms of rate. Compounds have to be used and produced at just the right quantities within a certain time in order to proceed properly, or at all. Temperature, for very basic physical chemistry reasons, is a key factor in controlling that rate.

So how does sweat play a role in that?

Perspiring does not occur primarily in order to keep the amount of fluid in homeostasis - urination does that, along with breathing (though sweating plays a small part). But it has a huge effect on body temperature. As we exercise, chemical reactions speed up and mechanical motion is taking place. Both those produce more heat energy, which raises the internal temperature.

But the body is constantly seeking homeostasis - an equilibrium within a narrow range around a central point. For humans, that's 98.6°F /37° C on average - a small deviation is within normal range. As we sweat, the excess heat energy is moved from inside the body to the outside, along the surface of the skin, carried along with the perspiration.

Outside the body a physical principle is at work - Newton's Law of Cooling. Inside too, but never mind for now. Ignoring advanced mathematics, it says essentially that warmer bodies lose heat to cooler ones. We get cooler, the air gets a little warmer. Air molecules collide with the sweat molecules and pick up some of the heat energy they contain. That lowers the temperature of the sweat, lowering our temperature in the process (on the outside).

The net effect is to take excess heat on the inside and move it to the outside, somewhat like a home air conditioner or a car radiator. That helps keep the internal temperature at a constant 98.6°F / 37°C.

That process takes place with breathing and just simple exposure. But sweating makes the process much more efficient, since water can carry a lot more heat than air does alone.

So, though it may have its unpleasant aspects, be thankful you perspire. After all, if you lacked sweat glands like your dog does, you'd look very silly panting.