Learning from Maughan & Shirreffs
The scientists who proved milk rehydrates better than sports drinks—and created the "150% Rule"
The Story
For decades, athletes were told to "drink when thirsty" or "just drink water."
Professors Ron Maughan and Susan Shirreffs from Loughborough University proved both approaches wrong.
Their research demonstrated that:
- Thirst is a lagging indicator—by the time you're thirsty, you're already dehydrated
- Plain water isn't the best rehydration fluid
- The amount you drink matters less than what you retain
Their work has shaped the hydration guidelines of the International Olympic Committee and transformed how elite athletes recover.
Who are Maughan & Shirreffs?
| Credential | Detail |
|---|---|
| Ron Maughan | Professor at Loughborough University; IOC Medical Commission member; primary architect of Olympic nutrition guidelines |
| Susan Shirreffs | Professor at Loughborough University; Theme Leader for Nutrition Society; specialist in hydration and fluid balance |
| Known For | The 150% Rule; Beverage Hydration Index; "planned drinking" vs. "drinking to thirst" research |
Together, they've published decades of research that forms the foundation of modern sports hydration science.
What ISP Students Learn
Lesson 1: The 150% Rule
Here's the math problem that Maughan and Shirreffs solved:
If you lose 1 kg of sweat, how much do you need to drink to replace it?
Most people say 1 liter (1:1 replacement). Wrong.
The reality: When you drink a lot of fluid, your body produces urine to regulate blood chemistry. Some of what you drink gets excreted before it's absorbed.
Their finding: You need to drink approximately 150% of the weight lost to fully restore fluid balance.
| Lost | Need to Drink |
|---|---|
| 1 kg (2.2 lbs) | 1.5 liters |
| 2 kg (4.4 lbs) | 3 liters |
What this means for young athletes: Weigh yourself before and after training. Multiply the weight lost by 1.5 to know how much fluid you need.
Lesson 2: What You Drink Matters More Than How Much
Their groundbreaking Beverage Hydration Index (BHI) study compared how different beverages affect fluid retention:
| Beverage | BHI Score | Interpretation |
|---|---|---|
| Skimmed Milk | 1.58 | Best—significantly better than water |
| Oral Rehydration Solution | 1.54 | Clinical gold standard |
| Full-Fat Milk | 1.50 | Excellent retention |
| Orange Juice | 1.39 | Good retention |
| Sports Drinks | 1.10 | NOT significantly better than water |
| Water | 1.00 | Reference baseline |
| Coffee/Tea | 1.00 | Same as water (no diuretic effect in habituated users) |
The surprise: Common sports drinks barely beat water for rehydration. Milk crushes them.
What this means for young athletes: Chocolate milk isn't just a tasty treat—it's one of the best recovery fluids available.
Lesson 3: Why Milk Works So Well
The "milk mechanism" explains why dairy outperforms engineered sports drinks:
| Factor | How It Helps |
|---|---|
| Electrolyte density | Natural sodium and potassium maintain the osmotic gradient |
| Protein coagulation | Casein forms a "curd" in the stomach, slowing emptying |
| Gradual delivery | Slower release prevents the spike that triggers urination |
The key insight: Fast absorption isn't always good. Gradual delivery means more retention.
What this means for young athletes: Post-workout, reach for chocolate milk before sports drinks.
Lesson 4: Sodium Is the Key to Retention
Water alone triggers urination because it dilutes your blood, suppressing the hormones that tell your body to hold onto fluid.
Their recommendation: For rapid rehydration after heavy sweating, fluids should contain:
- Standard: 0.5–0.7 g/L sodium (about 20-30 mmol/L)
- Heavy sweaters: Up to 1.5 g/L sodium
This is why oral rehydration solutions (used to treat dehydration illness) work so well—they're designed around sodium.
What this means for young athletes: If you're a heavy sweater, add electrolytes to your rehydration strategy. Don't just drink water.
Key Takeaways
| Lesson | One-Liner |
|---|---|
| The 150% Rule | Replace 1.5x what you lost to actually rehydrate |
| Milk beats sports drinks | Higher BHI score = more fluid retained |
| Sodium = retention | Electrolytes prevent urination before absorption |
| Planned drinking works | Don't wait until you're thirsty |
How This Shows Up at ISP
Maughan & Shirreffs' hydration science shapes the Bio Skill Tree:
- The 150% rule is taught for post-training recovery
- Milk is emphasized as a recovery beverage
- Students learn to weigh before/after to calculate fluid needs
- The BHI concept teaches critical thinking about beverage marketing
When ISP students think about hydration, they think about retention, not just consumption.
Planned Drinking vs. Drinking to Thirst
This is one of the biggest debates in sports nutrition. Maughan and Shirreffs' position:
| Context | Recommendation |
|---|---|
| Short exercise (<1 hour) | Drink to thirst is fine |
| Endurance/heat (>1 hour) | Planned drinking necessary |
Why thirst fails for athletes:
- Thirst lags behind actual deficit by 1-2%
- By the time you feel thirsty, performance is already impaired
- Athletes given free access only replace 50-70% of sweat losses
Their goal: Not 100% replacement during exercise (which can be dangerous), but preventing deficits >2%.
The Caffeine Myth
For decades, athletes were told to avoid coffee before competition because "caffeine is a diuretic."
Maughan debunked this:
- Studies showing diuretic effects used caffeine-naive subjects and mega-doses
- In habituated coffee drinkers, moderate caffeine shows NO significant difference in 24-hour urine volume compared to water
What this means for young athletes: If you normally drink coffee, you don't need to avoid it before competition.
Learn More
"Rehydration is not merely about drinking; it is about retention."