The Athletes’ Guide to Electrolytes
By Seiji Ishii
Editor in Chief
You know electrolytes matter – but do you know why? Here’s what each mineral does to keep you going.
Whether you’re trying to finish a marathon, powering through a high-intensity workout, or just trying to stay properly hydrated, understanding electrolytes is helpful.
These essential minerals are the unsung heroes keeping your body running smoothly. Let’s break down what’s in your hydration drinks and why each electrolyte matters.
What Are Electrolytes, Really?
Think of electrolytes as your body’s electrical system – they carry an electric charge and are responsible for maintaining fluid balance, conducting nerve impulses and contracting muscles.
You lose these crucial minerals through sweat, which is why plain water usually doesn’t cut it to keep you performing at your best.
The Big Players in Hydration
Sodium: The Hydration MVP
What it does: Sodium is the star player in fluid retention and absorption. It helps your body retain water and enables rapid hydration by enhancing water uptake in your intestines.
Why athletes need it: During intense exercise, you can lose 200-700 mg of sodium per hour through sweat¹. Low sodium levels lead to muscle cramps, fatigue, and in extreme cases, dangerous hyponatremia (where blood sodium drops so low it can cause seizures, coma, or even death).
The sweet spot: Quality sports drinks contain 400-1000 mg per serving to match actual sweat loss rates, especially during intense or prolonged exercise.
Potassium: The Muscle Manager
What it does: Potassium works hand-in-hand with sodium to regulate fluid balance, but its real superpower is muscle and nerve function. It’s essential for proper muscle contractions and preventing cramping.
Why athletes need it: Although you don’t lose as much potassium through sweat as sodium, deficiency can cause muscle weakness, cramping and irregular heartbeats². It’s particularly crucial for endurance athletes.
The sweet spot: Look for 80-200 mg per serving in your sports drink, with higher amounts for longer training sessions or if you’re a heavy sweater.
Magnesium: The Recovery Catalyst
What it does: Magnesium is a part of over 300 enzymatic reactions in your body. It supports muscle and nerve function, helps control blood sugar and is required for protein synthesis and recovery.
Why athletes need it: Intense training increases magnesium needs, and deficiency is linked to muscle cramps, fatigue and poor recovery³. Many athletes are already running low on magnesium due to their diet. It can serve as a great daily supplement to support a multitude of processes.
The sweet spot: Quality sports drinks typically contain 20-80 mg per serving, providing a helpful boost during longer training sessions.
Calcium: Beyond Bones
What it does: While famous for bone health, calcium is crucial for muscle contractions, including your heart muscle. It’s also a port of nerve transmission and blood clotting.
Why athletes need it: Calcium deficiency can lead to muscle cramps and impaired muscle function. During long training sessions, maintaining adequate calcium levels supports sustained performance.
The sweet spot: Most sports drinks contain 20-100 mg per serving, complementing your dietary intake.
Chloride: The Unsung Hero
What it does: Chloride works primarily with sodium to maintain fluid balance and is a significant component of stomach acid, supporting digestion.
Why athletes need it: You lose chloride along with sodium when you sweat. It’s essential for maintaining proper hydration and preventing the muscle cramps associated with electrolyte imbalance.
The sweet spot: Most quality sports drinks focus on getting the sodium right, then let chloride follow naturally. Look for products that use either sodium chloride for a more direct replacement of sweat losses or sodium citrate for easier digestion and better taste.
The Science of Absorption
The magic happens when these electrolytes work together. Sodium and glucose create a transport system in your intestines that dramatically speeds up water absorption⁴ – this is why sports drinks are more effective for rapid hydration than plain water.
The ideal ratio matters too. Too much of any single electrolyte can actually slow absorption or cause GI distress. That’s why quality sports drinks are formulated based on research into sweat composition and absorption rates.
When Do You Actually Need Them?
For workouts under an hour, water is usually sufficient.
However, when you’re training for more than 60 minutes, in hot conditions, or if you’re a heavy sweater, electrolyte replacement becomes crucial for maintaining performance and preventing muscle cramps. For most, that 400 mg range is adequate while those very salty sweaters will approach upwards of 1000 mg. Note how relative it can be.
Many athletes also use electrolyte drinks during recovery or on rest days – especially those following low-carb diets, intermittent fasting or whole-food diets that are naturally lower in sodium.
Your kidneys excrete more sodium when insulin levels are low⁵ (which happens when you don’t eat as many carbs or as often), so replacing electrolytes helps maintain energy levels and prevents the fatigue that accompanies sodium deficiency. Athletes on low-carb diets call this the “Keto Flu.”
Conclusions
Understanding electrolytes isn’t just for science nerds – it can help you understand why you need them in your training and recovery. Each mineral has a specific job, and when they work in harmony, they keep your body running smoothly.
Next time you sip on your bottle, you’ll know exactly what’s working behind the scenes to keep you hydrated, energized and performing at your best. Your muscles will thank you.
References
Exercise and Fluid Replacement. Medicine & Science in Sports & Exercise 39(2):p 377-390, February 2007. DOI: 10.1249/mss.0b013e31802ca597
Wartella, E. A., Lichtenstein, A. H., & Boon, C. S. (Eds.). (2010). Front-of-Package Nutrition Rating Systems and Symbols: Phase I Report. https://www.ncbi.nlm.nih.gov/books/NBK209844/
Gröber U, Schmidt J, Kisters K. Magnesium in Prevention and Therapy. Nutrients. 2015 Sep 23;7(9):8199-226. doi: 10.3390/nu7095388. PMID: 26404370; PMCID: PMC4586582.
Kaunitz, J. D., & Akiba, Y. (1995). Intestinal water and electrolyte transport. Physiology Reviews, 75(1), 23-67. https://doi.org/10.1152/physrev.1995.75.1.23
DeFronzo R. A. (1981). The effect of insulin on renal sodium metabolism. A review with clinical implications. Diabetologia, 21(3), 165–171. https://doi.org/10.1007/BF00252649