Critical Power and Critical Speed give us more than a training anchor.
They give us a way to understand how an athlete's fitness is currently organized.
Once CP/CS is positioned relative to power or speed at VO₂ max, we can describe an athlete's physiological state — not who they are, but where they are right now.
This post introduces those states.
No prescriptions yet. No zones. No workouts.
Just clarity.
From Measurement to Meaning
CP/CS defines the highest intensity an athlete can stabilize and absorb repeatedly.
Power or speed at VO₂ max reflects the athlete's aerobic ceiling.
The relationship between those two values tells us how much of that ceiling the athlete can actually use.
That relationship matters more than any single number on its own.
The House Model
To describe this relationship, we use a simple architectural model.
- The ceiling represents Critical Power / Critical Speed (CP/CS).
- The roof represents power or speed at VO₂ max.
- The peak of the house represents peak power or peak speed output.
- The space between the ceiling and the roof is the physiological attic space.
This attic space describes how much intensity exists above what can be stabilized, but below maximal aerobic output.
A large attic means there is a wide gap between capacity and utilization.
A small attic means a large portion of aerobic capacity can be expressed sustainably.
Neither is good or bad.
They describe state, not talent.
What We Mean by Physiological State
A physiological state is a snapshot of how the aerobic and anaerobic systems are currently balanced.
States are:
- Temporary
- Responsive to training
- Expected to change over time
They are not identities.
They are not permanent classifications.
They simply describe where adaptation is most available right now.
The Three Physiological States
Once CP/CS and VO₂ max are established, athletes generally fall into one of three states.
These states are defined by the ratio between CP/CS and power or speed at VO₂ max.
1. Anaerobic Physiological State
An athlete is in an anaerobic physiological state when:
CP / CS is below ~85% of power or speed at VO₂ max.
In house terms:
- The roof is high
- The ceiling is relatively low
- The attic space is large
This indicates that the athlete has meaningful aerobic capacity, but cannot yet utilize much of it sustainably.
There is a wide gap between what the athlete can do briefly and what they can absorb repeatedly.
This is not a flaw.
It is a condition.
2. Balanced Physiological State
An athlete is in a balanced physiological state when:
CP / CS sits between ~85–88% of power or speed at VO₂ max.
In house terms:
- The roof and ceiling are closer
- The attic space is moderate
This reflects a system where aerobic capacity and sustainable output are reasonably aligned.
The athlete can access a solid portion of their aerobic ceiling without excessive cost, while still leaving room for adaptation in either direction.
Balanced does not mean finished.
It means aligned.
3. Aerobic Physiological State
An athlete is in an aerobic physiological state when:
CP / CS exceeds ~88% of power or speed at VO₂ max.
In house terms:
- The ceiling sits very close to the roof
- The attic space is small
This indicates an athlete who can utilize a large percentage of their aerobic capacity sustainably.
They are efficient.
They are durable.
They extract a high return from the capacity they have.
Again, this is descriptive — not evaluative.
Why States Matter
Different physiological states respond differently to the same training stress.
What produces rapid adaptation in one state may produce stagnation or excess fatigue in another.
This explains why:
- Training blocks that once worked can stop working
- Two athletes can follow the same plan and diverge
- "More effort" often fails to solve the problem
Until the state is understood, training decisions are guesses.
Once the state is clear, decisions can be made intentionally.
What Comes Next
This post defines the states.
The next step is understanding how training modalities are selected based on state — and why the same tools are not always appropriate at the same time.
That is where the real return on investment appears.
Next: how training focus changes by physiological state — and why timing matters as much as effort.
