Preload with Sodium for Long Rides on Hot Days?

In North Central Texas this year we’ve had an unusually high number of 100+ degrees before Summer even started. Two of my friends had to be treated for heat exhaustion in the emergency department and one was kept in the hospital overnight. Starting Monday we’re in for at least 7 days in a row of 100+ degree days. The hottest time here is usually from the mid-part of July through August so it’s probably going to get even hotter.
If you live here and ride frequently you definitely get adapted to the heat.
I heard Andy Blow of Precision Hydration interviewed on a couple of other cycling related podcasts. has an online tool to help you estimate how much sodium you will need to take on board for long intense rides on a hot and/or humid day based on how much you sweat and how salty it is. I sweat somewhat more than average and my sweat isn’t unusually salty. The online tool recommended that before a long ride on a day that was forecast to be unusually hot and humid, I preload electrolytes by drinking some water the night before with one of their PH 1,500 mg tabs and then, on the morning before the ride, so the same. I did that recently and also added a 500 mg tab to my Camelback and I was fine during the ride. It appears the extra sodium helped me retain more water, I.e. I didn’t have to pee as much or as often, and my weight was a pound or two higher after the ride than usual.
In summary I seemed to tolerate it well and I think it helped but it’s difficult to know for sure.
What do the rest of you think? Is there a downside to this? Is it overkill?


I’m in the UK so don’t know availability in Texas. I have salt tablets which you swallow as necessary and it’s not tied to what’s in your water. The container they come in has recommendations on how many to have depending on conditions during your ride. The other thing to do is just carry some salted peanuts.

@CCR_TX, I’m a big fan of pre-hydration. You can look up some research on that to learn more, but the overall goal with the high sodium preload is to increase plasma volume (PV). So your weight gain was likely an effect of that, and overall a positive effect in that kind of heat.

There is always the health consideration of high sodium intake, but for acute needs that is a reasonable approach to boost PV. It’s another arrow in your quiver! I used to do the same thing on hot days before short track races mid-summer. I would use the Skratch hyper hydration mix the evening before and then again 60-90 min pre-race.

Another vote for pre-hydration here. Skratch as @ryan mentioned is great. I’ve played around with a mix I found in Stacy Sim’s Roar - she recommends 1L of water mixed with salts and glucose for hyperhydration, but you can get “good enough” with two scoops of Skratch in a 1L bottle the night before.

The home-brew I’ve settled on, again based on what Stacy wrote in Roar:

1L bottle of water (I use the Zefal Magnums!)
3/4 tsp table salt
1 3/4 tsp sodium citrate (available in bulk on Amazon, great additive for homemade sports drinks)
3-4TBSP dextrose (same as glucose) to flavor and aid absorption

Fair warning: this mix is quite a bit “saltier” tasting than Skratch would be, but it works for me.

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Whether hyper-hydration strategies are warranted , in my opinion, is more related to whether hydration opportunity is limited than it is to outright heat exposure. But I’m sure others have a differing opinion.

The reason for this is that there are often negative (GI) consequences to significant amounts of hyper-hydration.

First and foremost I typically try to maximize my ability to carry or replenish fluids.

  1. Larger water bottles (e.g. SOMA Further / Zefal Magnum as mentioned above)
  2. Carrying a water filter (Katadyn Be Free has been the best)
  3. Additional bottle cages (Sks Anywhere works well).

However, sometimes “hyper-hydration” is the “best solution”

One thing not mentioned is the use of glycerol as a plasma volume expander.

Pro-tip: You want Food-grade, “liquid” glycerol. In my experience the powdered versions are difficult to mix in water / difficult to drink.

Great info, thanks, the filter will be useful on long rides. When I see a red ring around the base of a water fountain, I know likely from an iron-laden well or bad city water.