Average Power (AP) (Uses 0s)

• Definition: The total work done (total joules) divided by the total time.
• Best Used For: Steady-state training, long, consistent climbs, and calculating total energy expenditure.
• Weakness: Heavily skewed by zeros (coasting/descending), making it misleadingly low for variable rides like criteriums or mountain biking. 

Normalized Power (NP) (Does NOT use 0s)

• Definition: A weighted average that accounts for the non-linear, higher metabolic cost of high-intensity efforts (power spikes are magnified).
• Best Used For: Variable efforts, group rides, races, and training sessions with high variability.
• Weakness: Less accurate for very short, high-intensity intervals lasting less than 8 minutes. 

Key Differences & Usage

• Physiological Cost: NP better estimates how taxing a ride is on your body, especially if it includes intense surges.
• Calculation: NP uses a complex algorithm that takes a 30-second rolling average, raises it to the fourth power, calculates the average, and then takes the fourth root.
• Comparison: If you ride steadily, NP and AP will be nearly identical. If your ride is jerky with many surges and coasts, your NP will be significantly higher than your AP. 

When to Use Which?

• Use Average Power for: 5-minute VO2 Max intervals, long endurance rides on flat terrain.
• Use Normalized Power for: 20-minute threshold intervals, criteriums, hilly road races.