If you train with a power meter, sooner or later you will see the term W′ (W prime).
Many riders see this number after testing or inside performance analysis, but very few really understand what it means when the race gets hard.
The simple explanation I give to my athletes is this: W′ is the amount of work you can do above Critical Power before you blow up. Not before it hurts. Not before it feels hard. Before you actually cannot hold the power anymore. And this is exactly what happens in races.
Critical Power is your engine. W′ is your battery
Critical Power (CP) is your sustainable level.
W′ is the extra energy you can use when the intensity goes above that level.
I usually explain it like this:
– CP = your engine
– W′ = your battery
Every time you go above CP, you use the battery.
Every time you go below CP, the battery slowly recharges. When the battery is empty, the legs don’t care how motivated you are.
You slow down.
Why two riders with the same FTP can race very differently
This is something I see all the time when coaching.
Two riders with the same threshold, but completely different race performance.
Example:
Rider A CP = 300 W W′ = 12 kJ
Rider B CP = 300 W W′ = 24 kJ
Same threshold. Very different rider.
Rider B can:
– follow attacks
– handle steep climbs
– repeat hard efforts
– survive aggressive races
Rider A is usually better at:
– time trials
– long steady climbs
– constant pace efforts
This is why FTP alone never tells the full story.
Why you feel good… until suddenly you don’t
You know this feeling.
You follow moves.
You feel strong.
Power is high but still under control. Then one more surge… And you are gone.
This is W′.
Every time you go above CP, you are spending from a limited tank. If the race keeps changing pace and you never get real recovery, the tank slowly empties. When it reaches zero, the legs just stop working.
It’s not mental.
It’s physiology.
W′ recovery is what makes good racers
One of the biggest differences between levels is not only CP.
It’s how fast W′ comes back.
Strong racers can:
– go above CP
– recover below CP
– go again
– and again
– and again
This is why races feel harder than training.
Training is controlled.
Racing is not.
If you want to perform in road races, gravel, MTB or cyclocross, you need to train not only power, but also the ability to repeat hard efforts.
How I train W′ with my athletes
There are three different goals depending on the rider.
1. Increase W′ itself
For riders who lack punch or explosive power.
Workouts I often use:
– 30/30 intervals
– 40/20 intervals
– short VO2 efforts
– repeated climbs
– sprint into hard efforts
These increase the amount of work you can do above CP.
2. Improve W′ recovery
This is one of the most important qualities for racing. Good sessions:
– over / unders
– race simulations
– microbursts
– variable power intervals
3. Raise Critical Power
Sometimes the best way to improve race performance is not more anaerobic work.
It’s increasing CP. If CP goes up, every surge costs less.
Example:
Before
CP = 280
Surge = 360 → +80
After
CP = 300
Surge = 360 → +60
Same race. Less damage.
This is why aerobic training never stops being important. Even for punchy riders.
Why I use W′ in my coaching
I don’t look at W′ just because it’s an interesting number. I use it because it explains things that threshold alone cannot explain.
With CP and W′ we can understand:
– why you get dropped
– why you explode late in races
– why you are good at attacks or not
– why some intervals work better than others
Inside my coaching system and on platforms like Vekta, this helps build training that is specific for the rider. Every athlete is different. Training should be different too.
Final thought
If you only look at FTP, you see part of the picture.
If you understand CP and W′, you understand how races really work.
And when you understand that, training becomes more specific, more effective, and more realistic.
That’s where real progress starts.
Matteo Cigala
Founder & Head Coach