Originally Posted by
OBoile
I'm not sure the linked article really backs up your position here.
First, hyponatremia results in sodium levels that are too low. This would indicate the need to take electrolytes, particularly sodium, and that increased fluid consumption should be balanced with increased electrolyte consumption.
Second, the level your kidneys can excrete isn't all that relevant if your sweating out a bunch of fluid as well. The 1 liter per hour level doesn't include how much you sweat.
Finally, the examples given are all people that consumed far more than 1 liter of water per hour, which seems to indicate the stomach/intestines can absorb more than that amount... otherwise they wouldn't have had any issues.
Have a go at a a couple pass climbs in the heat and report back. IME 1 liter/hour is my limit with appropriate electrolytes. I have heard that RAAM riders train to absorb a little more than that, and that it's possible, but I've never seen anyone do it.
It's true that the linked article doesn't mention a case of high volume consumption of water and electrolyte. Drinking a gallon/hour of Gatorade while riding in the heat would be an interesting experiment. Anyone?
Data points: July 26 I did 154 miles and 10,000', temperature on the last pass was only 80° at bottom, 100° at top, full sun, and then the last 35 miles at over 90°. Nice weather, really. I went through about 5 liters of water in ~11 hours elapsed, averaged 14.7 in the saddle, very slow this year. Out of shape. Then backpacked in the mountains this past weekend, 5 hours up in ~90°, 2.5 liters water. Faster coming down, about the same temp, 2 liters. Peed every hour.