Normalized Power vs. Average Power: Why You Shouldn’t Just Look at Average Power

A Real-World Confusion

You’ve just finished a road race, and your head unit shows an average power of 210W. But you know you pushed 350W on the climbs, dropped to nearly zero on the descents, and spiked to 800W in the final sprint. Did this race really put the same stress on your body as riding a steady 210W?

Clearly not. This is exactly why Normalized Power (NP) exists.

Average Power: Simple but Flawed

How It’s Calculated

Average Power is calculated very intuitively:

Average Power = the arithmetic mean of all power data points

If you record power once per second for an hour, that’s the average of 3,600 data points.

The Fundamental Problem: Physiological Cost Is Not Linear

The relationship between the body’s energy expenditure and power output is not linear — it’s exponential. In simple terms:

• The extra energy cost of going from 200W to 300W is far greater than going from 100W to 200W
• Alternating between 100W and 300W burns more energy than riding steadily at 200W
• Yet the average power in both cases is identical

This is why looking at average power alone seriously underestimates the true intensity of a variable-effort ride.

Normalized Power: A More Accurate Intensity Metric

Calculation Steps

NP was designed by Dr. Andrew Coggan and is calculated in four steps:

Step One: 30-Second Rolling Average

Apply a 30-second rolling average to the raw power data. This step simulates the body’s physiological lag in responding to changes in power — your body doesn’t react instantly to momentary power fluctuations.

Step Two: Raise to the Fourth Power

Raise each rolling average value to the fourth power:

Each value → value⁴

This step is the key to the whole calculation. Raising to the fourth power weights high power outputs far more heavily than low power outputs, which closely mirrors the nonlinear nature of the body’s energy expenditure.

Step Three: Take the Average

Calculate the arithmetic mean of all the fourth-power values.

Step Four: Take the Fourth Root

NP = ⁴√(the average of all the fourth-power values)

The Mathematical Intuition

Why the fourth power? Research shows that during high-intensity exercise, metabolic cost is proportional to power raised to roughly the third to fifth power. The fourth power was chosen as the best approximation after extensive empirical validation.

Real-World Comparison Examples

Example One: Steady Riding vs. Interval Riding

Metric	Rider A (Steady)	Rider B (Intervals)
Riding Pattern	Steady 200W for 60 minutes	400W for 1 min + 100W for 1 min, repeated 30 times
Average Power	200W	250W
Normalized Power	200W	~320W
Perceived Fatigue	Moderate	Extreme

Notice that Rider B’s NP is far higher than their AP, which more accurately reflects the physiological stress caused by interval riding.

Example Two: Criterium vs. Time Trial

Metric	Criterium	Time Trial
Duration	90 minutes	40 minutes
Average Power	185W	275W
Normalized Power	245W	278W
NP/AP Ratio	1.32	1.01

Because a criterium involves frequent acceleration, deceleration, attacks, and recovery, its NP is far higher than its AP. A time trial has steady output, so the two values are close.

Variability Index: Quantifying How Steady Your Ride Was

From the relationship between NP and AP, we can derive a useful metric:

Variability Index (VI) = NP / AP

VI Value	Meaning
1.00-1.02	Extremely steady (time trial, indoor trainer)
1.02-1.06	Fairly steady (solo training, climbing)
1.06-1.13	Moderately variable (group rides, rolling terrain)
1.13-1.25	Highly variable (criterium, mountain roads)
> 1.25	Extremely variable (cyclocross, attack-style riding)

Training Applications of VI

• Time trial training: Target a VI below 1.05, and practice holding steady output
• Pacing strategy: A VI that’s too high on a long ride indicates uneven pacing and wasted energy
• Race analysis: Compare VI across different races to see which ones had better pacing strategy

Intensity Factor (IF): Normalizing NP Further

IF = NP / FTP

IF Value	Corresponding Intensity
< 0.75	Recovery / easy ride
0.75-0.85	Aerobic endurance
0.85-0.95	Sweet spot / tempo
0.95-1.05	Threshold
1.05-1.15	VO2max intervals (short duration)
> 1.15	Anaerobic / neuromuscular (very short duration)

Note: An IF above 1.0 is possible, but only during short (typically under 30 minutes), high-intensity efforts. If your IF for a full hour is above 1.0, your FTP is likely set too low.

When Should You Look at AP? When Should You Look at NP?

Situations Where Average Power Is Useful

• Estimating energy expenditure: AP × time gives a more accurate figure when calculating kilojoules and calories burned
• Mechanical efficiency analysis: Comparing the aerodynamic efficiency of different bike setups
• Power meter calibration checks: On a steady ride, AP and NP should be very close

Situations Where Normalized Power Is Useful

• Training load assessment: All TSS-based calculations use NP
• Intensity comparison: Comparing intensity across different types of rides
• Pacing strategy: Pacing analysis for races and long rides
• Training zone verification: Confirming whether a workout stayed within its target zone

For Riders Without a Power Meter

Even if you don’t have a power meter, understanding the concept of NP is still valuable. If you train by heart rate, heart rate naturally has a “smoothing” quality similar to NP — it doesn’t instantly follow changes in power, and it has its own natural lag and smoothing effect. However, heart rate is also affected by external factors like temperature, hydration, and fatigue, so a power meter remains the more reliable tool.

Conclusion

Normalized Power isn’t just a number — it represents how much stress your body actually experienced. Next time you look at your ride data, find the NP first; it will tell you a more accurate story. And the bigger the gap between NP and AP, the more you should ask yourself: does this riding pattern actually match your training goals?

Related Reading

• The Complete Guide to Reading Power Data: What NP, IF, and VI Really Mean, and How to Spot Problems From a Single Ride
• How to Interpret Training Data: What Power, Heart Rate, and TSS Are Really Telling You
• Power Meter Data Analysis: Reading Key Metrics in Strava and TrainingPeaks
• Post-Race Power Data Analysis: How to Find Room for Improvement From Your Race File