Hydration Beyond Water: What Your Body Actually Needs When You Train in the Heat

Most of us have had that afternoon. You finished camp hours ago, you've been sipping water all day, and you still can't shake the headache, the heavy legs, or that foggy feeling that's making your inbox feel like an impossible task.

The easy assumption is that it was a hard workout or a bad night of sleep, and sometimes it is. On hot summer training days though, water on its own often isn't doing the full job. What your body is also asking for is the sodium that's left with your sweat.

What's Happening When You Sweat

Sweat is mostly water, but it carries minerals out with it. Sodium is the big one, with potassium and magnesium coming along in smaller amounts.*

Sodium has a few quiet but important jobs in your body. It helps you retain the water you drink, supports your blood pressure when your heart rate climbs, and keeps your muscles firing the way they should during exercise.*

How much sodium you lose depends on the person. Some people sweat out about 500mg per liter, while others lose two or three times that amount.* If your shirt and hat come home from a hot Saturday camp covered in white salt streaks, or if your sweat regularly stings your eyes and tastes salty on your lip, you're on the higher end of that range. For heavier sweaters, drinking water without replacing sodium can leave you feeling worse, because your body needs the salt to actually hold onto the fluid you're putting in.*

When Water Is Enough

Not every workout needs a hydration strategy. A 45-minute camp on a mild morning, an indoor online session with the AC running, or a strength block where you're barely sweating will all be fine with water. Drink in the morning, sip during, drink again after, and you're set.

The picture changes when heat, length, or intensity ramps up.

When You Need More

You'll want electrolytes in the mix when any of the following are true:

• Your workout runs longer than an hour

• The temperature is in the mid-70s or hotter

• You're training back-to-back days

• You're heat-acclimating after a stretch of indoor training

• You're prepping for a HYROX, DEKA, or Elevation Everest event

In any of those situations, you're losing more sweat and sodium than water alone can replace.*

What to Actually Do

Before a hot workout

• Drink a glass of water with a pinch of salt and a squeeze of lemon, or have a small electrolyte drink alongside breakfast

• Start the workout already topped off, since catching up midway through a hot camp gets hard once you're behind

During a long or hot workout

• Put an electrolyte drink in your bottle instead of plain water

• A useful rule of thumb is that if you can taste the minerals, you're in the right zone. If it tastes like flavored water, the sodium is likely too low to make a difference

After your workout

• Replace both fluid and sodium, and let food do most of the work

• Easy options include a salty snack with your post-workout meal, a cup of broth, pickles, deli meat, cheese, or just salting your food a bit more generously on training days

What to Look For on the Label

Once you decide to add an electrolyte product to your routine, the label can be confusing. Here's what actually matters and what to skip.

Look for:

• At least 300mg of sodium per serving. This is the number that matters most.* Anything under 200mg is closer to flavored water in practical terms.

• A balanced sodium-to-potassium ratio. Your body loses roughly four to five times more sodium than potassium through sweat, so a product with around 1000mg of sodium and 200mg of potassium is well matched to what you're actually losing.* Products that overload on potassium tend to miss the mark.

• A small amount of carbohydrate (5 to 10g per serving) if you're using the drink during a long or intense workout. Sodium and carbs together activate a transporter in your gut that pulls fluid in faster, which is part of why traditional sports drinks include sugar by design.* Zero-sugar options are fine for shorter sessions or post-workout sipping.

• Magnesium glycinate or magnesium citrate if magnesium is included. These forms absorb well and are easier on the stomach. Magnesium oxide is cheaper and appears in many products, but it is poorly absorbed and can cause GI issues.*

  
  

Be cautious of:

• High doses of artificial sweeteners, especially sucralose and acesulfame potassium. Some members tolerate them fine, while others get cramping or stomach upset mid-workout and don't always connect it to the drink.

• Sports drinks with 20 to 30g of added sugar and only 100 to 150mg of sodium. That ratio is the opposite of what you want for a hot workout.

• Wellness products that bolt electrolytes onto something else, like a "hangover cure," "immune booster," or "beauty drink." Those are usually multivitamin products with a sprinkle of sodium, not real hydration support.

• Caffeinated electrolyte products during or after a hot workout. They're fine as a pre-workout if you tolerate caffeine well, but caffeine is mildly diuretic and works against what you're trying to do once the sweat is really flowing.

• Vague "proprietary blends" that don't list specific milligram amounts of sodium, potassium, and magnesium. If the label is vague, the formulation usually is too.

The Signs You're Falling Behind

The signs that you're under-hydrated or low on sodium tend to show up quietly. You might notice:

• A mid-afternoon headache that arrived out of nowhere

• Foggy thinking through your last meeting of the day

• A sharp calf cramp that wakes you up at 2 a.m

• Dizziness when you stand up too fast in the kitchen

• A workout that flattens you in a way it normally wouldn't*

When you start seeing those patterns line up on training days, the fix is usually simple. A little more sodium, water sipped across the day, and real food eaten alongside it will move the needle quickly.

The Takeaway

Summer hydration is one of the easier things to get right once you know what your body is asking for. Water handles most days. On the harder, hotter ones, some sodium and a bit of thoughtful timing turn a draining afternoon into a workout you can recover from, and a day you can stay sharp through.

Pay attention to how you feel a few hours after camp, adjust what you're doing based on what you notice, and you'll dial it in pretty quickly.

References

• Sawka, M. N., Burke, L. M., Eichner, E. R., Maughan, R. J., Montain, S. J., & Stachenfeld, N. S. (2007). American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine & Science in Sports & Exercise, 39(2), 377–390. ↩

• McDermott, B. P., Anderson, S. A., Armstrong, L. E., et al. (2017). National Athletic Trainers' Association Position Statement: Fluid Replacement for the Physically Active. Journal of Athletic Training, 52(9), 877–895. ↩

• Baker, L. B. (2017). Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability. Sports Medicine, 47(Suppl 1), 111–128. ↩

• Maughan, R. J., & Shirreffs, S. M. (2010). Dehydration and rehydration in competitive sport. Scandinavian Journal of Medicine & Science in Sports, 20(s3), 40–47. ↩

• Périard, J. D., Eijsvogels, T. M. H., & Daanen, H. A. M. (2021). Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies. Physiological Reviews, 101(4), 1873–1979. ↩

• Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise, 48(3), 543–568. ↩

• Cheuvront, S. N., & Kenefick, R. W. (2014). Dehydration: physiological issues. Nutrition Reviews, 73(s2), 79–86. ↩

• Schuchardt, J. P., & Hahn, A. (2017). Intestinal Absorption and Factors Influencing Bioavailability of Magnesium: An Update. Current Nutrition & Food Science, 13(4), 260–278. ↩