Estimated read time: 4.12 minutes (about as long as it takes me to pull the trigger on a new pair of super shoes)

Hey Performance Nerds! Jonah here. 🤓

Quick note before we start:

I'm bringing this one back because electrolyte questions always spike in the summer.

The answer isn't "never use them." It's knowing when they help, when they are optional, and when water plus normal meals is enough.

Most short training runs don't require electrolytes. In the heat, they can help if you're drinking more, sweating heavily, or trying to recover quickly.

This isn't anti-electrolyte. It's pro-context.

A lot of runners use electrolytes by default, even when the run doesn't demand them.

Sodium matters most when your fluid replacement starts catching up to your sweat losses, not every time you lace up.

Here's what you'll learn today:

(Augie drinks from mud puddles with zero electrolytes and still outruns me to the mailbox.)

Hytro makes blood-flow-restriction gear, basically BFR built into training shorts so athletes can get a strong stimulus with lighter loads.

I only work with partners here when I believe in the product and the science behind it.

They are trying to better understand what runners actually want from performance and recovery gear. If you can spare a few minutes, filling this out would be a huge help.

They are also adding an incentive: 1 in 20 people who complete the survey will win $100.

Which, naturally, should be spent directly on the super shoe savings account.

The gel I race with and keep recommending because the formula makes sense: BETA FUEL delivers 40g of carbs per gel through a 1:0.8 maltodextrin-to-fructose ratio.

That ratio is the point. It helps you use multiple carb transporters, push higher intake, and keep the gut calmer when fueling gets serious.

Stryd gives runners power, pacing, and mechanical metrics that can make training decisions clearer when pace and heart rate do not tell the whole story.

See this week's full Stryd training tip at the end of this newsletter.

Start with water, then decide on sodium.

The relationship between sodium and fluid matters more than how much sodium you lose.

For many runners, your blood sodium tends to rise during exercise.

Rise, not fall.

Unless you're drinking enough to replace most of your sweat, your body is naturally concentrating sodium in your blood when you run.

Sodium helps your body hold onto the fluid you drink.

It can also help keep more of that fluid in the bloodstream when sweat losses are high.

Electrolytes become relevant when fluid replacement hits 50 to 70% of losses. That usually happens around 2 to 3 hours of running, or earlier in hot conditions when you're drinking more aggressively.

The principle: match sodium to fluid replacement, not to your sweat test results.

Precision testing is optional, but helpful if you're an exceptionally heavy sweater, racing in hot conditions, or you know hydration feels tricky for you.

Unlike fueling, sweat losses vary widely between athletes. Testing can give you a clearer baseline to personalize from.

Hyper-salty mixes can hurt palatability and cause gut issues anyway.

Keep solutions moderate and drink to thirst.

Skip the pre-run sodium for most training.

The exception: if you're racing in heat, racing long, or often start underhydrated.

In that case, use 275 to 420 mg sodium per 100 mL of fluid in the 4 hours pre-run.

This helps your body retain more fluid. Capsules work if salty drinks taste bad.

Otherwise? Save your money.

This is where it usually matters.

Under 2 hours: most runners can skip sodium here, unless heat, sweat rate, or rapid rehydration needs change the plan.

2 to 3 hours, heat, or high sweat: consider 300 to 600 mg sodium per hour via drinks, gels, chews, or capsules. Drink to thirst, not to a schedule.

3 hours or more, marathons, or ultras: use the same range. Personalize to your gut tolerance and conditions.

Important: Sodium won't "fix cramps" by itself. Its job here is fluid balance, not magic.

Salty foods or a normal meal usually cover it. Your kidneys conserve sodium fast after exercise.

Exceptions:

Otherwise? Food beats special drinks.

"Should I replace all my sweat sodium?"

No. You'll likely overshoot plasma sodium if fluid replacement is low. Most runners only replace 50 to 70% of fluid losses anyway.

"Does sodium improve performance?"

Only if it helps you drink appropriately and keep balance. It isn't a magic performance enhancer. It's mainly a fluid-balance tool.

"Electrolytes stop cramps?"

Cramping is multifactorial. Sodium helps with fluid balance, but it won't fix fatigue, pace, or neuromuscular changes that lead to cramps.

Bottom line:

The question isn't how salty your sweat is. It is how much water you're replacing.

Start by matching sodium to your bottles and conditions, not just your sweat test results.

Jonah

Welcome to the prove you're a nerd section. Each week, I ask a question about a common running science myth.

Answer correctly, and you'll be entered into a weekly raffle to win a package of Jonah's favorite supplements.

Last Week's Results: Lactate

Last week's poll asked: "A runner sees lactate rising during a hard tempo. What does that number actually mean?"

Most runners knew the main idea: lactate is not just waste. It is part of the fuel-shuttling system, and a rising value usually means the effort is pressing closer to the edge you can sustain.

The correct answer?
A. The body is producing and shuttling more lactate, which can be reused as fuel, while the effort is nearing its sustainable limit

A lactate number is a signal of production, clearance, and intensity all at once. Your body can reuse lactate, but as the pace rises, production can start outpacing clearance.

That is when the number becomes useful: not as a panic button, but as a clue that the workout is creeping toward the limit.

Here's how the votes shook out:

A. The body is producing and shuttling more lactate, which can be reused as fuel, while the effort is nearing its sustainable limit - 217 (about 79 percent)
B. Lactate is the waste product causing the burning feeling, so the workout is failing once it rises - 15 (about 5 percent)
C. Lactate means the muscles have run out of oxygen, so the effort has become completely anaerobic - 40 (about 15 percent)
D. Lactate only matters after the workout, when the liver turns it back into glucose - 2 (about 1 percent)
Total votes: 274

The wrong answer that pulled real votes was C, and I get why. Lactate rising often gets talked about like a switch into anaerobic metabolism.

But running is not that binary. Oxygen use does not disappear. The body is still using multiple fuel systems at once.

Bottom line?
Rising lactate is not proof the workout is failing. It is a context signal: how hard the effort is, how well you are clearing and reusing lactate, and whether the pace is still sustainable.

I've been getting a lot of questions about Leg Spring Stiffness, so this week I want to show how I use it.

Stryd defines LSS as the force you create divided by how much your leg compresses during ground contact.

In plain English: how stiff your leg acts as a spring when you land.

I don't use it to judge one run.

I use it to watch the trend across similar marathon long runs.

If my LSS goes from 8.6 to 8.7 to 9.1 to 9.8 kN/m on the same type of long run, that gets my attention.

That is why I check it during blocks with strength work, plyos, hills, strides, and faster running.

Those sessions are there to improve the neuromuscular side of training: how well my legs handle and apply force.

LSS doesn't prove the block worked.

But if the long runs are comparable, it gives me one more sign that the work is showing up in marathon-specific running.

One caveat: tired legs can hide the signal. If I’m deep in marathon training, I may not see the cleaner LSS trend until the taper lets my legs freshen up.

The comparison has to be boring: similar shoes, surface, pace, terrain, and long-run setup.

Why it matters:

This week, pick one repeatable long run and save the LSS. Then compare it to the same kind of run later in the block.

Try it on your next run