Learning from Bergström & Hultman
The Swedish scientists who invented carb-loading by sticking needles into muscles
The Story
In the 1960s, nobody knew what was actually happening inside a working muscle during exercise.
Scientists could measure what went in (food, oxygen) and what came out (CO2, sweat). But the muscle itself was a "black box"—they couldn't see inside.
Jonas Bergström changed that.
He developed a technique to safely extract tiny pieces of muscle tissue using a hollow needle. For the first time, researchers could measure the actual fuel levels inside human muscles before, during, and after exercise.
Working with Eric Hultman in Stockholm, he made a discovery that revolutionized endurance sports: the more glycogen (stored carbs) in your muscles before a race, the longer you could perform.
And then they found something even more interesting: you could "supercompensate"—force muscles to store MORE glycogen than normal through specific diet manipulation.
This discovery created "carb-loading," the pre-race ritual that every marathoner now knows.
Who are Bergström & Hultman?
| Scientist | Contribution |
|---|---|
| Jonas Bergström | Developed the muscle biopsy needle; clinical nephrologist at St. Erik's Hospital, Stockholm |
| Eric Hultman | Clinical chemist who developed micro-methods to analyze tiny tissue samples; Karolinska Institute |
Together with Bengt Saltin, they formed the team that established the fundamental laws of sports nutrition in the 1960s.
What ISP Students Learn
Lesson 1: Fuel Determines Endurance
The 1967 study that changed everything tested three diets:
| Diet | Muscle Glycogen | Time to Exhaustion |
|---|---|---|
| High fat/protein (5% carbs) | 0.6 g/100g | 59 minutes |
| Normal mixed diet | 1.7 g/100g | 126 minutes |
| High carbohydrate (82% carbs) | 3.5-4.7 g/100g | 189 minutes |
The relationship was nearly perfect: double your glycogen, double your endurance.
This wasn't theory. It was measured directly from muscle tissue.
"The correlation between starting glycogen and time to exhaustion was almost perfect."
What this means for young athletes: What you eat in the DAYS before competition matters more than what you eat the morning of.
Lesson 2: Supercompensation Is Real
Bergström and Hultman discovered that if you depleted your muscles (through hard exercise) and then loaded them with carbs, they would "overshoot" normal storage levels.
Like squeezing a sponge dry before dunking it in water—it absorbs more than if it started partially wet.
This "supercompensation" could increase muscle glycogen to 2-3x normal levels.
What this means for young athletes: For big events, the taper + carb-loading combination works. It's not bro-science—it's directly measured science.
Lesson 3: Depletion Is Local, Not Global
One of their most elegant experiments used one-legged cycling. Athletes exhausted only ONE leg, then ate the same high-carb diet.
Result: Only the depleted leg supercompensated. The resting leg didn't.
This proved that glycogen storage is controlled locally by the muscle itself, not just by hormones in the bloodstream.
"Contraction sensitizes the specific muscle fibers to receive fuel."
What this means for young athletes: You have to deplete the muscles you want to load. A runner doing arm exercises won't supercompensate their legs.
Lesson 4: The Original Protocol Was Brutal (And Got Refined)
The original "classical" carb-loading protocol was effective but miserable:
- Exhaustive exercise 7 days before race
- Days 2-4: Near-zero carbs (the "depletion phase")
- Days 5-7: Massive carb intake
- Day 8: Race
Athletes during the depletion phase were irritable, fatigued, and got sick more often.
Later research (by Costill and Sherman) showed you could skip the depletion torture. Just tapering training while eating high carbs for 3 days achieved nearly the same supercompensation without the misery.
What this means for young athletes: Modern carb-loading doesn't require suffering. Just taper training + eat more carbs for 2-3 days.
Key Takeaways
| Lesson | One-Liner |
|---|---|
| Fuel = endurance | More muscle glycogen directly means longer performance |
| Supercompensation works | You can store more glycogen than "normal" with proper loading |
| Depletion is local | Each muscle adapts to ITS own training |
| Skip the suffering | Modern protocols work without extreme depletion |
How This Shows Up at ISP
Bergström and Hultman's discoveries form the scientific foundation of carb-loading education in the Bio Skill Tree:
- Pre-competition nutrition planning includes the "taper + load" protocol
- Students learn why glycogen matters for their specific sport
- The difference between "daily fueling" and "competition fueling" is taught
- The local adaptation principle connects to sport-specific training
When ISP students prepare for big competitions, they're using protocols that trace directly back to a hospital in Stockholm in 1967.
The Biopsy Legacy
The muscle biopsy technique Bergström developed is still used today. It's one of the only ways to directly measure what's happening inside muscle tissue.
Every sports nutrition study that mentions "muscle glycogen levels" owes a debt to a Swedish nephrologist who figured out how to safely sample human muscle without surgery.
Learn More
"You must deplete to reload. That's the local factor."