Is water consumption when exercising directly related to heat index?? (hot, record)

[papafox]

In preperation for a 28 mile trek on a VERY remote beach in the far, far Bahamas next year!!, I am carefully calculating H2O consumption over a certain time periods based on different temp/DP combos.

So I am wondering……all other things being equal, is the heat index number the most accurate figure to determine how much water I will need to drink?

In other words, would I need the same amount of H2O with a temp of 84 and a DP of 74 as I would with a temp of 90 with a DP of 60??

Both of these T/DP combos give me the same heat index number.

Again, lets assume all else is equal, such as sun angle, diet, heart rate, etc, etc.

Any info about this would be VERY helpful!!

Thanks

[Shalop]

It might be a productive use of your time to go out on long hikes in hot weather and record how much water you consume at different values of temps and dew points.

This way, you will become familiar with your water consumption rates, and no surprises will arise when you go on that super-long trek.

BTW, I think you'd need way more water at 84/74 than you'd need at 90/60. I just speak from personal experience of going on three-to-five-mile runs during our humid summers. Heat Index generally won't give you all the information you'll need. Be very cautious of 70+ dew points if you're gonna be active for that long (that's when you'll need a lot of water, as the body sweats rapidly in such humidity).

[divisionbyzero0]

i agree with shalop, dewpoint is a great factor

[Cambium]

It's an interesting question.

When dewpoints are high your body overheats because the sweat doesnt evaporate as fast but if dews are low with hotter temps you might might need more water to replenish whats evaporating.

I think your consumption is based on the physical workout more then the weather itself? How does your body react to temps..how does it react to dews? Me? I sweat a lot more with higher dews so I need to replenish more.

Maybe you don't need more water with low dews and hotter temps because your body can cool down naturally by the sweat evaporating better.

Or maybe you need the same H2O amount at both examples. I wouldn't use heat index because there won't be a heat index # with a temp of 95 and DP of 40 yet you might be sweating more and need more water cause its hot and dry.

Cool question.

Good luck with the crazy hike and I'm curious how much you drank now. Lol

[Shalop]

Originally Posted by Shalop

Heat Index generally won't give you all the information you'll need.

One more thing:

You should always remember that the Heat Index is just a contrived value that doesn't really mean very much, whereas the air temperature and dew point are intrinsic properties of the air and are therefore more important values to pay attention to.

[Cambium]

When I hiked Algonquin (2nd tallest in NY) in August, I went through 2 16oz bottles plus Gatorade and it wasn't enough. Temps & DPs started in the 50s then DPs rose to 60s, temps to 70s. 8hrs of hiking.

Also factor in what you ate the night before as well.

Also.. there's a general rule that you should be drinking every 20 minutes or something like that.

I wonder if we ate a whole watermelon right before a hike if that would help. lol

If you're doing 28 miles in the tropics in summer, without any place around to get drinks, I suggest you pack heavy with a ton of liquid

[Cambium]

Just went for a 4 mile run. Noticed I needed more water then previous runs. Dew point is higher this morning. Most likely related. Plus little sleep & little food yesterday might have contributed to the thirst. Drank 17 ounce bottle of water after I was done.