Re: How to plan Urine production in relation to fluid intake exp?

Your effort is interesting. I have some points to tell you that will 
affect your work. First of all the sources of water input for the body are 
2: oral intake and water produced in metabolism. However the sources of 
output are many such as loss thru skin, loss of water during 
respiration, sweat, feces, and lastly urine output. During your 
experimental work you will have to keep this in mind that whatever you 
take in orally will not appear equally in urine and the problem you will 
face is that you won't be able to calculate the water loss through other 
sources. When completely at rest, the urine output is expected to increase 
propotionally with increase in water intake. In the other case if you 
maintain a constant exercise (activity) level instead of rest, the urine 
output will still increase in proportion. However it may practically be 
very difficult for you to maintain the constant activity level while you 
take different quantities of water and failing to do so will alter the 
results as inconsistency in exercise will cause changes in loss of water 
through sweat. If more water is lost in sweat in one case than other then 
the change in urine output will not be as expected. That is the sweat 
water loss should be constant throughout the experimentation when you want 
to study the water loss accompanied by exercise.

Another option could be that first you can calculate the changes in urine 
output in relation to changes in water intake at complete rest. Then with 
changing intake on the same pattern right from the beginning but altering 
exercise level, you could show that the water loss in urine does not 
increase as expected due to exercise as the water loss is diverted to 
sweat.

Now we come to the expected results; when you study distilled water you 
will observe increases in urine output with increases in water intake. 
However if you study hypertonic solution (compared to plasma) the urine 
output is supposed to decrease. Its important to note that the solution 
should be hypertonic than plasma i.e. body's fluid medium. Any other 
solution that you are considering hypertonic that is actually hypotonic 
compared to plasma will not give you decreesed urine output as it is still 
adding water to body being hypotonic than plasma.