Why Watts Scale to the Athlete—and Why Cycling Still Gets It Wrong
There’s a persistent myth in cycling that refuses to die:
“Bigger riders are faster on the flats because they produce more power.”
It sounds like physics. It isn’t.
There is no law of physics—none—that says higher absolute watts make you faster without considering aerodynamics and mass. Power is not speed. Power is simply the cost of moving through resistance—and that cost scales to the athlete.
The Masters Worlds Epiphany
At a Masters World Time Trial qualifier, I finished 3rd—just seconds off the win.
Post-race, we compared numbers:
- Rider 1: 380W
- Rider 2: 360W
Then they looked at me:
“You must have done at least 345W.”
I told them the truth:
298W.
They didn’t believe it. They assumed something was wrong with my power meter.
But nothing was wrong.
They were looking at absolute cost.
I was operating on efficiency.
They needed 360–380W to move their system through the air at that speed.
I didn’t.
Power Is Personal—Like Heart Rate
We don’t compare heart rate across athletes.
- One rider’s threshold: 185 bpm
- Another’s: 165 bpm
No one says the 185 rider is “stronger.”
Because heart rate is relative to the individual.
Power should be treated the same way.
Watts are not a universal badge of strength.
They are an individual cost metric, determined by:
- Body size
- Mass
- Frontal area
- Position
A bigger athlete must spend more energy to go the same speed.
That’s not an advantage.
That’s scaling.
What Actually Determines Speed
At steady speed, cycling performance is governed by resistance:
- Aerodynamic drag (dominant on flats and in wind)
- Rolling resistance (scales with mass)
- Gravity (dominant uphill, scales with mass)
Power is simply what’s required to overcome those forces.
Speed determines required power—not the other way around.
If two riders go the same speed:
- The rider with lower drag uses less power
- The heavier rider uses more
No exceptions.
The Porsche vs. the Audi
Imagine:
- Audi RS7 → 650 hp
- Porsche 911 → 450 hp
The Audi has vastly more “absolute power.”
Yet the Porsche is often faster.
Why?
Because speed isn’t about engine size—it’s about efficiency.
- Audi (Big Rider):
Massive engine, but more mass and drag. Power is spent overcoming itself. - Porsche (Efficient Rider):
Less power, but cleaner shape. More of that power becomes speed.
Cycling has been obsessed with building bigger engines.
The real goal has always been to become the Porsche.
What Science Actually Says: Allometric Scaling
Decades of research show that:
- Absolute watts are misleading
- Even W/kg is incomplete on flat terrain
For time trials, a better predictor is:
W / kg^0.32
This accounts for how drag and mass scale differently as athletes get larger.
My 298W vs. My competitors 380W at the World Qualifiers wasn’t a fluke.
It was physics.
What the Experts Say
“More power isn’t necessarily better when aerodynamics are considered. We win with speed, not impressive power numbers.”
The human body is a “bluff body”—responsible for ~85% of aerodynamic drag. Two riders with identical power can produce completely different speeds based on shape alone.
Why the Industry Gets This Wrong
Two reasons:
1.
Expertise Gap
Most coaches understand physiology.
Fewer understand aerodynamics or fluid dynamics.
So they optimize what they can measure easily:
→ Watts
Not what actually determines performance:
→ Speed per watt
2.
Industry Incentives
The industry can sell:
- Bikes
- Wheels
- Helmets
It cannot sell:
- Narrower shoulders
- Limb proportions
- Body geometry
So morphology gets ignored—even though it’s one of the biggest performance drivers.
This Isn’t About Advantage
This isn’t about saying lighter riders are “better.”
It’s about understanding:
Power scales to the athlete—just like heart rate.
The only meaningful question is:
How effectively does this athlete convert power into speed?
That’s efficiency.
That’s performance.
Technical Sidebar: Why 298W Can Beat 380W
The Problem with W/kg
W/kg assumes resistance scales perfectly with body mass.
It doesn’t.
- Mass scales ~x³
- Frontal area (drag) scales ~x²
So larger riders gain power potential—but also disproportionate drag.
The Potential Better Metric: W/kg^0.32
Example:
- 85 kg @ 380W → 91.7 scaled
- 65 kg @ 298W → 78.2 scaled
On paper, the bigger rider still wins.
But…
The Missing Piece: The Efficiency Gap
Scaling assumes average aerodynamics.
If a rider has:
- Lower CdA
- Better position
- Better morphology
They outperform the model.
They “break” the expected relationship.
The Real Takeaway
Stop chasing arbitrary watt targets.
Instead:
- Maximize scaled power (W/kg^0.32)
- Minimize CdA relentlessly
- Improve how power translates to speed
When you do that…
You become the rider the “big watt” athletes don’t understand.
Fuel your next breakthrough. Don’t miss new insights, workouts, and the launch of SMART Cycling.
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