I bonked on a ride last summer — not from lack of food, but from dehydration. It was 85 degrees, I was two hours into a long loop, and I’d only been sipping from one bottle. By mile 50 I had a splitting headache, my power numbers cratered, and I felt like I was pedaling through mud. Pulled into a gas station, drank two bottles of Gatorade, and sat on a curb for twenty minutes feeling stupid. The fix was so simple, and I’d just… forgotten to drink enough.
“Drink before you’re thirsty” sounds like a cliché until you experience what happens when you don’t.
How Much You Actually Need
The standard guideline is one standard bottle (500-750ml) per hour of moderate riding. That’s a reasonable starting point, but it varies a lot based on temperature, intensity, and how much you personally sweat. I sweat heavily — on hot days I can lose 1.5 liters per hour easily. I know this because I did the weigh-yourself-before-and-after test a few times. Every kilogram you lose during a ride is roughly a liter of fluid you didn’t replace.
On cool days with moderate effort, one bottle per hour is plenty. On a hot day with hard climbing, I go through two bottles per hour and still finish dehydrated. Learn your own sweat rate — it’s the only way to dial in hydration that actually works for your body rather than following a generic chart.
Water vs. Electrolyte Drinks
For rides under 90 minutes at moderate intensity, plain water is fine. Your body has enough stored sodium and electrolytes to get through. Beyond 90 minutes — or in serious heat — you need electrolytes, particularly sodium. Sweat isn’t just water; it’s salty water, and replacing the liquid without the salt creates its own problems (hyponatremia, which is rare but real).
I use Skratch Labs or Nuun tabs in one bottle and plain water in the other. The electrolyte drink handles mineral replacement; the plain water is there for when I want to rinse my mouth or cool my head without wasting the good stuff. Drinks with carbohydrates (like Gatorade Endurance or Maurten) do double duty as hydration and fuel, which simplifies things on really long days.
Recognizing When You’re Already Behind
The early signs of dehydration are subtle enough that you might blame them on fatigue: your power drops, you feel sluggish, maybe a mild headache starts. By the time you’re genuinely thirsty, you’re already 1-2% dehydrated — which translates to a measurable performance hit. Dark urine when you stop is a clear indicator you’ve been under-drinking.
If you start feeling confused, dizzy, or your skin stops sweating on a hot day, that’s no longer a performance issue — it’s a medical situation. Stop riding, find shade, and get fluids immediately. Heat illness escalates fast.
The easiest fix: set a timer on your bike computer or watch for every 15 minutes. Take two or three good sips each time it goes off. After a few rides this becomes automatic, and you stop having to think about it. My hydration problems disappeared once I made sipping a scheduled habit instead of relying on thirst signals.
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