Monday, March 30, 2009

Water, Water Everywhere....

but not a drop to drink?

Today I TAed my FAVORITE exercise phys lab (is it weird that i got that excited by that?) It was on Thermoregulation. And why do I enjoy it so much? Its about dehydration! And I am always dehydrated.

So here's a run down of what happens: we take one poor soul and make them ride a stationary bike for 60 minutes, at a pretty fast pace, while wearing a sweatshirt and sweatpants- and not letting them drink any water.
On top of this- they are having all sorts of things done to them like blood pressure, heart rate, and temperature taken, and, O yea, I had to take their blood by a figure prick 4 times.
All for the sake of science!

So basically
When one exercises his or her internal heat increases because of the mechanical energy of the muscles. A high body temperature can be dangerous because all of the chemical and enzymatic reactions that occur in the body to make everything function properly should be occurring around 98˚F, and when the body temperature gets too high the enzymes and proteins denature and become ineffective. In order to cool down the body, the four methods of heat removal can be used (conduction, convection, radiation and evaportation). The main method for cooling the body during exercise is through evaporative cooling, or sweating. When one sweats the fluid in the interstitial fluid moves up to the skin. In order to maintain osmotic pressure, the plasma from the blood then seeps into the cells. Due to this shift, the plasma loses volume which causes dehydration. (Costill, Dill).

During an exercise where the individual is more dehydrated, it becomes more difficult to pump the blood through the circulatory system due to the decreased volume. This problem is exasperated since during exercise, especially in the heat, there is more vasodilatation of the arteries and capillaries, and there is a significant amount of blood out by the skin attempting to release heat. All of these facts can work to increase the heart rate and blood pressure. The stroke volume, on the other hand, decreases due to these factors of there being a decreasing amount of blood to pump through the heart at each beat (Plowman et al., 420-421) .

So basically this is why its important to try water while you exercise! :)

As some of you have had to deal with - i go on kicks of trying to actually drink 8 cups of water a day- which usually leads to me drinking 8 cups before noon, having to pee every 5 minutes, and then swearing off water for a few days....

But - I'm going to go on a water challenge for myself and actually try to drink like a normal person!

And so this posting may have been a combination of my love/anti love of dehydration and my way of helping those in exercise phys with their lab report hahaha

Costill, D., Dill, D. (1974)“Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration” Journal of Applied Physiology. 37: 247-248.

Plowman, Sharon A., Smith, Denise L. (2008). Exercise Physiology for Health, Fitness, and Performance. Second edition, Philadelphia: Lippincott Williams and Wilkins.

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