Beating the heat with Hyperhydration

Dehydration is one of the biggest threats to cycling performance—especially in hot, humid conditions. Hyperhydration is a strategy that increases your body’s fluid reserves before you ride, helping you tolerate more fluid loss and delay the effects of dehydration.

By combining sodium, glycerol, or both, hyperhydration can expand blood plasma volume, lower heart rate and core temperature, and extend endurance. Think of it like carb-loading, but for fluids. Normally, your kidneys do an excellent job of balancing fluid levels, so drinking a lot at once or beyond your needs will trigger them to flush out the excess. Hyperhydration works by adding an osmotically active substance—something that helps the body hold onto water—to temporarily boost fluid stores.

The two most common options are sodium and glycerol. You’re likely familiar with sodium and its tendency to leave you feeling puffy or bloated after a salty meal. Glycerol, however, is less familiar to most people. It’s a liquid sugar alcohol with a mildly sweet, syrup-like taste. It’s common in toothpaste, shampoos, baked goods, and other food products, but is seldom used on its own in sport outside of hyperhydration protocols.

How It Works

• Sodium: 3 g/L of fluid (about 7.5 g of salt) with 20–25 ml/kg body weight of fluid. Retains ~60% of what you drink.

• Glycerol: 1.0–1.2 g/kg body weight with 20–25 ml/kg fluid. Retains ~39%.

• Sodium + Glycerol: Retention can jump to ~77%.

  
  

Example for a 150 lb (68 kg) athlete (1.5–3 hours pre-exercise)

Sodium

• Fluid: 20–25 ml/kg → 1.4–1.7 L

• Sodium: 3 g/L → 4.2–5.1 g sodium (≈10–13 g table salt)

• Retention: ~60% → ~0.9–1.0 L retained

Glycerol

• Glycerol: 1.0–1.2 g/kg → 68–82 g

• Fluid: 1.4–1.7 L

• Retention: ~39% → ~0.5–0.7 L retained

Sodium + Glycerol

• Same dosing as above (sodium + glycerol + 1.4–1.7 L fluid)

• Retention: ~77% → ~1.1–1.3 L retained

Best Times to Use Hyperhydration

• Long races in high heat or humidity

• Limited access to fluids on course

• Heat training sessions

• Back-to-back hot training or racing days

• Events where mid-race drinking isn’t practical

• Before bed to reduce overnight waking from thirst/urination

  
  

Things to Know

Hyperhydration isn’t for every ride. Extra fluid weight can be a disadvantage on hilly courses, and some riders experience GI distress. For example, when I first tried the highest recommended dose, it “cleared me out”—not ideal. Luckily, I tested it 2–3 hours before riding, so I was back to normal by start time, but it’s doubtful much fluid was retained.

Tip: Test in training, not on race day. Start with half a dose of glycerol + sodium—or even sodium alone—and build up. Track tolerance and fluid retention using a scale and notes on urine frequency/volume.

When used strategically, hyperhydration can help you stay cooler, stronger, and better prepared for racing in the heat. That’s the ultimate goal. Let me know if you give it a try or have questions!

Check out this AIS handout page for more info

Read another post on this topic here