Learning from David Costill
The father of American sports nutrition—who made carb-loading practical and hydration scientific
The Story
In the 1960s, David Costill was frustrated.
As a competitive swimmer and cross-country coach, he kept asking "why" questions about training. Why do some athletes handle heat better? Why does performance drop in the fourth quarter? Why do different diets produce different results?
Nobody had answers backed by data.
So Costill built a lab in a converted classroom at Ball State University—a 20x30 foot room with basic equipment—and started measuring. Within a decade, that tiny lab became the "Mecca of Exercise Physiology" in America.
His contributions are everywhere: the carb-loading protocol athletes actually use (not the brutal original), the science behind sports drinks, the understanding of how dehydration impairs performance. If you've ever drunk Gatorade or loaded carbs before a race, you're using Costill's science.
Who is David Costill?
| Credential | Detail |
|---|---|
| Role | Emeritus Professor, Ball State University; Founder of the Human Performance Laboratory |
| Known For | Modified carb-loading protocol, hydration science, post-exercise recovery windows |
| Background | NCAA swimmer, cross-country coach before becoming a researcher |
| Publications | A Scientific Approach to Distance Running, Inside Running |
Costill's lab trained an entire generation of exercise physiologists. He bridged the gap between European biochemistry and American coaching.
What ISP Students Learn
Lesson 1: Skip the Suffering—Carb-Loading Made Practical
The original Swedish carb-loading protocol worked, but it was brutal: days of near-starvation followed by carb gorging.
Costill asked: "Is all that suffering actually necessary?"
His 1981 study with William Sherman tested whether you could skip the depletion phase. The answer: yes.
| Protocol | Glycogen Stored | Side Effects |
|---|---|---|
| Classical (depletion + loading) | ~211 mmol/kg | Irritability, hypoglycemia, fatigue, illness risk |
| Modified (taper + loading only) | ~204 mmol/kg | Minimal |
Athletes achieved nearly identical glycogen levels just by:
- Tapering training for 3-4 days before the race
- Eating 70% carbohydrates during those days
No starvation. No misery. Same fuel tanks.
What this means for young athletes: Modern carb-loading is simple: rest more, eat more carbs, perform better.
Lesson 2: Dehydration Is a Performance Killer
When Costill started researching, coaches believed drinking during exercise was weak—it would cause "waterlogging" and cramps.
Costill proved this was dangerously wrong.
His experiments showed that losing just 2% of body weight through sweat caused:
- Elevated heart rate
- Increased core temperature
- Reduced performance
Losing 5%+ created serious heat illness risk.
"The runners restricted from drinking weren't tougher. They were slower and sicker."
What this means for young athletes: Drink when you're thirsty. The old "tough it out" approach was never based on science.
Lesson 3: The Post-Workout Window Is Real
Costill's lab documented that delaying carbohydrate intake by just 2 hours after exercise cut glycogen restoration rate by 50%.
The enzymes that rebuild your fuel stores are most active immediately after exercise. Wait too long, and you miss the window.
For athletes training multiple times per day (or competing on consecutive days), this matters enormously.
What this means for young athletes: Have a recovery snack ready. The clock starts when training stops.
Lesson 4: The Scientist Should Be in the Arena
What made Costill different was his own athletic background. He didn't just observe from the lab—he understood what athletes experienced.
His experiments often used elite marathoners, Olympic swimmers, and professional cyclists as subjects. He ran alongside his subjects. He knew what "bonking" felt like, not just what it measured as.
"The runner who understands their own physiology will outperform the runner who trains on blind faith."
What this means for young athletes: Learn the "why" behind nutrition advice. Athletes who understand their bodies make better decisions.
Key Takeaways
| Lesson | One-Liner |
|---|---|
| Skip the suffering | Taper + load works as well as starve + load |
| Hydration matters | 2% dehydration measurably hurts performance |
| Recovery windows are real | Eating sooner restores fuel faster |
| Know your physiology | Understanding "why" makes you a better athlete |
How This Shows Up at ISP
Costill's practical approach defines how we teach nutrition in the Bio Skill Tree:
- The "modified carb-loading" protocol is what we teach for competition prep
- Hydration education emphasizes the 2% threshold
- Post-workout recovery windows are part of every fueling challenge
- We teach the "why" behind every recommendation
When ISP students prepare for competition, they use the same evidence-based protocols Costill validated at Ball State.
The Hydration Debate
Costill's research led to guidelines recommending athletes "replace all fluid lost." Later researchers (notably Tim Noakes) argued this went too far, causing some athletes to overdrink.
The current consensus: drink to thirst, but don't ignore thirst. Both extremes—never drinking and forcing fluids—have problems.
At ISP, we teach individualized hydration based on the student's sport, duration, and environment.
Learn More
"A nutritional strategy is useless if the training has already destroyed the muscle's contractile proteins."