I pulled electrolytes entirely for a few weeks. The headaches came back.

Last month I split my runs into short-and-water, long-and-mix and said the headache was tied to the long ones. That post tested electrolytes-vs-water side by side. This time I went the other direction and just pulled the electrolytes out completely. Every run, every distance, plain water only. I wanted to see if the headaches would actually come back, or if I’d been talking myself into a rule that didn’t hold.

They came back. On the runs I expected, and not on the ones I didn’t.

The setup

A few weeks of nothing but plain water. No mix, no powder, no exceptions. Runs ranged from a brisk 5K up to a medium-long 20K. All of them in the early or late evening, which is when I actually run. Air temps over this stretch ran from about 60°F up to almost 90°F, so I got a real spread of easy nights and sticky ones.

Same as before, I wasn’t timing a stopwatch reaction. I was watching the dumb honest signals: did I get a headache, how bad, and how long did it hang around.

Short runs: still nothing

The 5Ks and the other short easy ones felt exactly like they did on the mix. No headache, no flatness, no difference during the run or after it. If anything this just re-confirms what I found last month. For an easy 5 or 6K, plain water is fine and the salt isn’t buying me anything I can feel.

That part I could set my watch to. Short and easy, plain water, no tax. Every time.

Medium to long: the headache I built this site around

The longer runs are where it fell apart, and it wasn’t subtle.

Somewhere past the short bucket, on the 15K and 20K nights especially, the old headache came back. Not a twinge. The bad one. The dull, all-over pressure that sets in a couple hours after I’m home and then just sits there. The kind that doesn’t clear from a glass of water or an ibuprofen, that I go to bed still feeling and only shake by the next morning. That specific overnight headache is the exact thing I built this whole site around, and I’d half-forgotten how much it wrecks an evening until I gave it back to myself for a few weeks.

So there it is, from the other side. Last month I proved the mix prevents it. This month I proved that taking the mix away brings it right back. Same trigger, same lag, same overnight clear. That’s about as clean as an n=1 gets: the headache tracks the electrolyte loss on the longer runs, and it’s tied to the activity, not to my sleep or a long day or whatever else I used to blame.

What I’m changing

I run a vest with two bottles plus a backpack bladder for the longer stuff, so the fix is about which container gets what.

Going forward: one vest bottle gets electrolytes dosed off the calculator, the other vest bottle is plain water, and if I need the backpack water on a long one, that’s plain too. One dosed bottle covers the loss that actually causes the headache. Everything else is just fluid, and plain water is easier to drink, easier to refill, and one less thing to mix before I head out.

That’s a step past last month’s rule. Back then it was “long runs get a dosed bottle, short runs get water.” Now it’s more specific about the ratio on a long run itself: I don’t need every bottle salted, I need about a bottle’s worth of electrolytes in the mix somewhere. The rest can be water.

There’s a nice side effect to this. Cutting the short runs down to water was the first halving of my electrolyte use. Going to one dosed bottle on the long runs instead of a full vest is the second. So I’ve roughly halved my usage again, which means the bulk salts I buy in one go now last twice as long. Doing the rough math on what’s left in the tubs, that pushes my next restock out to somewhere around November. I like a protocol change that fixes the headaches and stretches the supplies at the same time.

A few honest caveats, same as always:

• This is my body and my sweat rate. I land in the heavy-to-very-heavy bucket (see the sweat rate test), so one dosed bottle for me is probably more sodium than one dosed bottle for you.
• The heat is still climbing. At almost 90°F a single dosed bottle felt like enough on a 20K, but if August gets worse I may need a second one on the longest runs, and I’ll write it down here if it does.
• “One bottle’s worth” is where I’m starting, not a proven optimum. I know zero electrolytes is too little and I know a fully-dosed vest is more than I need. The right amount is somewhere in between and I’m going to spend the rest of the summer finding it.

For now the takeaway is the blunt one: the headaches are real, they’re electrolyte loss, and they show up on the medium and long runs exactly like the math said they would. I just needed to feel them again to believe it.

If you’ve run your own no-salt stretch and found a different line, tell me where yours sits.