It is one of the most common things I hear at the store.
"I drink water the whole run and I still cramped at kilometre 15." Or: "I felt completely flat and dizzy and I have no idea why." Or: "I bonked way earlier than I should have for how fit I am."
Most of the time, the conversation ends up in the same place. Not training. Not fitness. Electrolytes.
Most runners know the word. Far fewer actually understand what electrolytes do, why losing them derails a run so completely, and how simple it is to fix once you know what you are dealing with.
This is that conversation.
What electrolytes actually are
Electrolytes are minerals that carry an electrical charge when dissolved in fluid. The main ones runners need to pay attention to are sodium, potassium, magnesium, and chloride.
They are not a supplement category invented by sports nutrition companies. They are essential minerals your body cannot function without. Every muscle contraction, every nerve signal, every heartbeat depends on these minerals being present in the right concentrations in your cells and bloodstream.
When everything is in balance, your body does not advertise it. You just feel good and run well. When the balance tips, things start to break down fast, and the symptoms feel completely out of proportion to what is actually happening.
What happens when you sweat
Here is the part most runners miss.
Sweat is not just water. When you run, especially in summer heat, your body produces sweat to cool itself down. That sweat contains water, yes, but it also carries significant amounts of sodium, potassium, magnesium, and chloride out of your body with it.
Depending on your pace, the temperature, your body size, and your individual sweat rate, you can lose anywhere from 500ml to well over a litre of fluid per hour during a run. And with that fluid goes a meaningful quantity of electrolytes, particularly sodium.
Sodium is the most important electrolyte for runners to understand. It is the primary mineral that controls fluid balance at a cellular level. Sodium is what determines how much water your cells can actually hold, use, and retain. Without enough sodium, the water you drink does not stay where your body needs it. It passes through without doing its job.
This is why drinking more water does not fix the problem. If you are low on sodium, adding more water actually makes the imbalance worse.
Why the symptoms hit when they do
If you have ever felt fine for the first half of a run and then fallen apart in the second half, electrolyte depletion is almost certainly part of the story alongside with glucose depletion.
Here is why the timing works that way.
Your body has some reserves to draw on at the start of a run. Even if you did not fuel or hydrate particularly well beforehand, your muscles have stored glycogen and your blood has a baseline concentration of electrolytes that can carry you for a while.
But as the run continues and the sweating continues, those reserves get drawn down. By the time you feel the first sign that something is wrong - a cramp starting in your calf, a heaviness in your legs that was not there at kilometre 5, a light-headedness that comes out of nowhere - the depletion is already well underway.
This is the fundamental problem with waiting until you feel bad to address it. By then you are not preventing the issue, you are trying to recover from it mid-run. And recovery mid-run is much slower and much harder than prevention before the run even starts.
The three ways electrolyte loss shows up in runners
Cramping
Muscle cramps during or after running are one of the most classic signs of sodium and magnesium deficiency. The muscle cannot relax properly because the mineral signals that regulate contraction and release are out of balance.
Cramping that happens late in a long run, after you have been sweating for an hour or more, is almost always electrolyte-related. Cramping that happens early in a run is more likely a warm-up or intensity issue. Know the difference.
Feeling flat and dizzy despite drinking water
This is the one that confuses runners the most. You have been drinking consistently. Your water bottle is getting emptied. You should feel fine. But you feel heavy, your effort feels way out of proportion to your pace, and there is a dizziness or foggy quality to how you feel.
What is happening is that your sodium levels have dropped low enough that your body cannot properly absorb and use the water you are drinking. The fluid is not getting to where it needs to be. You feel dehydrated even though you have been hydrating because without sodium, the water cannot do its job.
Bonking earlier than your fitness should allow
When electrolyte levels drop significantly, your body shifts how it operates. Your perceived effort goes up, your ability to maintain pace drops, and your mental sharpness, which you need for pacing decisions and pushing through the hard parts, deteriorates.
If you are a well-trained runner consistently falling apart in the final third of your long runs despite decent nutrition, electrolyte timing and quantity is one of the first things worth examining.
How to actually fix it: a practical guide
Before your run
For any run over 60 minutes, especially in summer, start your electrolyte intake before you head out the door. A serving of an electrolyte drink mix 20 to 30 minutes before your run gives your body a baseline to work from before the sweating begins.
This is a habit most runners skip because they do not feel like they need it yet. The whole point is to get ahead of the depletion, not respond to it.
During your run
For runs between 60 and 90 minutes, aim to take in electrolytes at least once during the run, ideally around the halfway point. A tablet dissolved in your water bottle, a gel that contains sodium, or a salt capsule all work.
For runs over 90 minutes, plan to take in electrolytes every 45 to 60 minutes. Set a reminder on your watch if you need to. Do not rely on how you feel as your signal — as established above, by the time you feel it, you are already behind.
After your run
Recovery hydration is not just about refilling your fluid levels. It is about restoring the mineral balance your body needs to repair muscle tissue and recover properly. An electrolyte drink or a salty snack in the first 30 minutes after a long run makes a real difference to how you feel the following day.
What to look for in an electrolyte product
Not all electrolyte products are created equally. Here is what to pay attention to when you are choosing one.
Sodium content first. Sodium is the most important electrolyte for endurance running and it is the most commonly under-dosed in mainstream products. Look for at least 200mg of sodium per serving for easy shorter runs, and closer to 400 to 500mg per serving for longer runs in summer heat. If you are a visibly heavy sweater, someone who finishes runs with a white salt residue on their skin or clothing, you may need even more.
Watch out for sugar overload. Some electrolyte products, particularly the ones marketed to casual fitness, are essentially sports drinks with a lot of sugar and very little actual electrolyte content. Check the label. If sugar is the first or second ingredient and sodium is listed toward the bottom, it is more of a product for during exercise
Think about format. Tablets that dissolve in water are convenient and portable. Drink mixes give you more control over concentration. Capsules are the easiest to carry on the run. Gels with electrolytes let you combine fuelling and hydration in one. There is no universally right answer, just the format that works best for how you train.
Real food is also an option. Salted potatoes, pickle juice, and miso soup are all legitimate electrolyte sources that endurance athletes have used for decades. If you prefer a whole-food approach, these are worth knowing about.
What we carry at Frontrunners
We stock a range of electrolyte products chosen specifically for runners rather than just generic gym-goers. Here is a quick breakdown of what we carry and who each one suits:
Precision Fuel and Hydration (PF&H): Built around serious endurance sport with a strong focus on getting sodium concentrations right. Their drink mixes come in different sodium strengths (Low, Moderate, High) so you can match the product to your individual sweat rate. One of the most science-backed electrolyte brands available.
Nuun Tablets: Dissolve in water, low calorie, easy to carry in a pocket or pack. A great everyday option for runs under two hours where you want electrolyte support without a lot of sugar or calories. Widely liked and very convenient.
Skratch Labs: A clean, real-food approach to sports nutrition. Their hydration mixes use real fruit and simple ingredients with solid electrolyte content. Popular with runners who prefer to avoid artificial ingredients and flavours.
Salt Stick Tabs: Capsule format, easy to carry, straightforward sodium and electrolyte blend. Great for runners who do not want to carry a bottle but want reliable electrolyte support during long efforts. Pop a capsule at each hour mark and move on.
Xact Nutrition: A European brand with a strong scientific foundation. Clean ingredient list, well-balanced electrolyte profile, and a bit different from the North American brands most runners know. Worth trying if you are looking for something new.
Not sure which one is right for you? Come into any of our Frontrunners locations and we will ask you a few questions about how you train, how much you sweat, and what format works for your runs. Five minutes of conversation and you will leave with the right product for how you actually run.
Shop electrolytes and nutrition: https://frontrunners.ca/collections/nutrition
A simple rule to remember
If you are running for less than 45 minutes at easy effort, water is probably fine.
If you are running for over 60 minutes, especially in summer, especially at moderate to hard effort, electrolytes are not optional. They are part of your fuelling plan the same way your gels or your long run pace are part of your training plan.
Build the habit in training and race day takes care of itself.
The bottom line
Cramping, dizziness, early bonking. These are not signs of poor fitness. They are signs of a fixable problem with a simple solution. Understand what electrolytes do, get ahead of the depletion rather than responding to it, and choose a product that actually matches the sodium demands of the running you are doing.
Your long runs will feel different. Your race day will feel different. And you will stop blaming your legs for problems that were never really about your legs.
Come in and we will help you get it right.
Batu
Frontrunners Victoria
frontrunners.ca
