How should I use electrolytes during my sub-3 effort?
Electrolytes like sodium and potassium play a quiet but critical role in marathon performance. Here’s how to manage them without going overboard.
I was introduced to SaltStick tablets during my first sub-3 training block by a clubmate who swore they stopped his calves from cramping. For years, he’d struggled in the final stages of marathons - until he discovered the issue wasn’t his fitness but a depletion of sodium and key electrolytes. Whether or not that diagnosis was entirely accurate is still up for debate - the science linking salt loss directly to cramps is mixed - but it worked for him, and I’ve kept a tube of SaltSticks on my shelf ever since.
Electrolytes are minerals like sodium, potassium, magnesium and calcium that help regulate fluid balance, muscle function and nerve signals. Sodium - which is the main component of table salt - is the one you lose most rapidly through sweat. For sub-3 marathoners running close to their aerobic threshold for the best part of three hours, the cumulative loss can be significant. Add in heat, humidity or a naturally salty sweat rate, and the risk of electrolyte imbalance becomes very real.
Most runners get plenty of sodium from their day-to-day diet - often without realising it. A shop-bought prawn cocktail sandwich, for example, can contain almost an entire day's worth of recommended sodium. Bread, cereal, cheese and processed foods all carry surprisingly high amounts. And soy sauce? It’s more than four times saltier than seawater. Other electrolytes are easy to come by too. Bananas are a good source of potassium. Milk contains calcium. If you eat a varied diet, you’re probably getting enough most of the time.
But if, like me, you eat a very low-sodium diet by choice, you may be more vulnerable to depletion during long races or sweaty training blocks. Electrolyte supplements can help top up your levels, but it’s best to test them in advance. Products like SaltStick, Precision Hydration or even common sports drinks like Lucozade Sport include added electrolytes. Just make sure to check the label - and never rely on something handed out at an aid station unless you’ve tried it before. Nothing new on race day.
There’s no universal strategy, but a good rule of thumb is to replace what you’re likely to lose. I tend to take one SaltStick capsule around mile 10 and another near mile 20, paired with water and gels. Others preload with electrolytes the day before or dissolve them in bottles. The key is to experiment in training, observe how your body responds and find a routine that works for you.
A poor electrolyte strategy might not matter in perfect conditions - but when things get tough, it can be the difference between finishing strong and falling apart.
Enjoyed this article? Help keep Sub-3 running — support us with a coffee.
To help fund the running of the site, Sub-3 is an Amazon Associate and earns from qualifying purchases. We only recommend gear or kit that has genuinely helped in our own running and that we believe is worth considering.
