What do the different Training metrics mean (FTP, Weighted Power, Variability Index, Workout Intensity, Workout Load Score)?

A power meter is a powerful tool for effective training, but to get the most out of it, you need to understand key metrics like Functional Threshold Power, Weighted Power (WP), Variability Index, Workout Intensity (WI), and Workout Load Score (WLS). Read on to learn about these terms and how they apply to your training.

1. Functional Threshold Power (FTP): This is the maximum power you can sustain for an hour without fatiguing, often determined by a field test.
2. Weighted Power (WP): When you ride with a power meter, your power output fluctuates due to terrain, wind, and other factors. Weighted Power (WP) accounts for this variability by calculating an average power that reflects the true physiological cost of your ride. Unlike simple average power, WP estimates what your average power would have been if you had ridden at a constant wattage throughout, providing a more accurate measure of your effort and how metabolically challenging the ride was.
3. Variability Index (VI): VI measures how smooth or variable your power output was during a ride, calculated by dividing WP by Average Power. A VI closer to 1.0 indicates a more consistent effort.
4. Workout Intensity (WI): WI is the ratio of WP to your FTP. It allows you to compare the intensity of different sessions or races, even as your FTP changes over time.
5. Workout Load Score (WLS): Based on the duration and intensity of your workout, WLS provides a single numerical value representing the overall training load. For example, a 60-minute session at 100% FTP equals 100 WLS points.

Understanding these metrics enables you to analyze your rides with greater precision, helping you to quantify the true load of your training both for individual rides and over time. By applying these insights, you can train more effectively and become a faster rider.