Sweat Rate on Spinning Class: 64.294795 ounces/hr

Weighed myself before Keith's spinning class tonight. Naked and dry.

Before: 170 lbs

After: 167.8 lbs

But I have to add to my loss the amount of water that I drank during the spinning class. I was very careful to drink exactly one bike water bottle. Afterwards I used a measuring cup to see how much it holds.

Water during spinning: 2 3/4 cups of H2O = 1.435 lbs

So I add 1.435 to the difference between start and finish weight:

Sweat lost: 3.635 lbs

Time of workout: 52 minutes

Loss per minute: .0699038461 lbs/minute

Loss per hour: .0699038461 x 60 = 4.1942307 lbs/hr

Using the conversion that 1 gallon of H2O = 8.35 lbs:

Loss in gallons: .5023030 gallons

Loss per hour in ounces: 64.294795 ounces/hr

Wow! I lose a lot more sweat in an hour of spinning than I do in an hour of swimming. My sweat rate per hour of swimming was significantly less. Generally workout books say that you should drink 6-10 ounces per 15 minutes of workout. That would be 24-40 ounces. I seem to need more. Of course, this was a very intense workout with my pulse high for most of the session. The temperature in the room was about 84 degrees.