Health Library / Lifestyle
This content is for education only and is not medical advice. I'm a fitness coach, not a physician. Talk to your doctor before starting any medication, hormone, supplement, or new exercise program, especially if you have a medical condition or take prescriptions.
Training in Hawaii is a different job from training in a temperate climate, and the electrolyte industry has done a very good job of making something simple sound complicated.
Let me separate what matters from what's being sold.
Your thirst signal gets less reliable. Older adults genuinely sense thirst less acutely, which means "drink when you're thirsty" — decent advice at 25 — becomes a lagging indicator. You can be meaningfully down before you notice.
Your ability to regulate heat declines. Sweat response changes, cardiovascular strain in heat is higher, and several common medications make it worse. Diuretics affect fluid directly. Beta blockers blunt the heart rate response you'd normally use to handle heat. Some blood pressure drugs and antidepressants affect sweating.
So the 55-year-old training at noon in Kihei is working with less margin than they had at 30, and usually hasn't adjusted anything.
Performance drops before you feel especially thirsty. Strength, endurance and particularly your ability to tolerate heat all degrade. Perceived effort climbs — the same session feels harder.
It also affects concentration and mood, which is why the afternoon slump is sometimes just fluid.
Urine colour is the useful one. Pale yellow is fine. Dark is a signal. It's crude, it's free, and it beats any formula.
Weigh before and after a long session in heat. Weight lost during exercise is essentially all fluid. If you're consistently down a couple of pounds after training, you're not drinking enough during it.
Drink across the day rather than in bursts. Large volumes at once mostly end up in the toilet.
I'm deliberately not giving you an ounces-per-day number. Those formulas ignore body size, sweat rate, heat, humidity, what you ate and what you're doing, and the variation between people is larger than the number.
You lose sodium, potassium, magnesium and chloride in sweat — mostly sodium, and how much varies a lot between people. Some people finish a session with salt crusted on their face. Some never do.
When electrolytes genuinely matter: sessions over about an hour, especially in heat. Heavy sweaters. Multiple sessions a day. Anyone cramping regularly. And the outdoor worker in Hawaii sweating for eight hours, who is in a completely different situation from someone doing 45 minutes in air conditioning.
When they mostly don't: a normal gym session under an hour, in a person eating ordinary food. Food contains sodium and potassium. A meal handles it.
The industry has successfully convinced a lot of people that they need an electrolyte packet to survive a walk, and that's a marketing achievement rather than a physiological requirement.
That said — the packets are cheap, they're harmless for most people, and if having one makes you drink more, that's a real benefit through the side door. Just know what you're buying.
If you have high blood pressure, heart failure or kidney disease, added sodium is not automatically fine. That's a genuine conversation with your doctor rather than a default.
Hyponatremia — sodium diluted too low in the blood — from drinking large amounts of plain water during prolonged exertion. It's the opposite of dehydration and it has killed endurance athletes.
The confusing part is that early symptoms look like dehydration: headache, nausea, confusion. So people drink more water and make it worse.
Risk goes up with long events, slower participants who have more time to drink, hot conditions, and the well-intentioned advice to drink as much as possible. If you're out for hours in heat, sodium isn't optional.
Know the difference, because it matters.
Heat exhaustion: heavy sweating, cold clammy skin, weakness, nausea, dizziness, headache, fast weak pulse. Stop, get to shade or air conditioning, cool down, sip fluids. Take it seriously.
Heat stroke: body temperature climbing high, skin that may be hot and dry because sweating has stopped, confusion or altered behaviour, slurred speech, possible loss of consciousness. This is a 911 emergency. Cool aggressively while help is coming. People die from this and the altered mental state is the sign that it's crossed over.
Confusion in the heat is never something to push through.
If you've just moved here or you're coming back from a mainland winter, your body takes roughly ten days to two weeks of regular heat exposure to adapt — you'll sweat earlier, sweat more efficiently and lose less sodium.
Until that's happened, train in the cooler parts of the day and accept that your numbers will be down. That's not detraining. That's a thermoregulation problem, and it resolves.
Watch your urine colour. Drink through the day, not in gulps. Add sodium for long hot sessions and don't bother for short ones. Train early or late in summer. Know the heat stroke signs.
And if you're on a medication affecting fluid or heart rate, ask your doctor what that means for training in this climate specifically. Most people never think to ask, and it's exactly the question that applies here.
Last updated September 30, 2026