This article explains step by step how to analyze the heart rate/ power relationship.

**Heart rate / power chart**

**Rainbow line**

The rainbow line tells about the sequence of your real time data. The sequence of the colors is: yellow (start), green, light blue, blue, red and purple (end). Eg.: the color code of a ride of 60 minutes: 00-10': yellow / 11-20': green / 21-30': light blue / 31-40': blue / 41-50': red / 51-60': purple.

**Big squiggly line**

The big squiggly line shows what your heart rate did in relation to your power-output.

**Black line**

The black line is the best fit line that is drawn through the big squiggly line, presenting all coordinates of the heart rate/power-speed relationship.

**Slope**

The slope is defined as the tangent of the angle with the best fit curve through the squigly line.

**Zero position**

This is the point on the heart rate/power relationship chart where the best fit black line hits the heart rate axis (y-axis).

**Colour code**

Colour code for training zones in the abcis (y-axis) expressed as heart rate and in the ordinate (x-axis) expressed as power.

**Markers**

Markers for aerobic (AT) and anaerobic threshold (ANT), if present, for the given workout or view.

**Glossary of terms**

**Adapted power/speed**

Adapted power/speed is calculated by a special algoritme on your power/speed data that takes into account the variability of power/speed data. Therefore, adaptated power is a better indicator than the average power to understand the true metabolic demands of a workout.

**Load index**

The Load index (LI) is a calculated number that takes into account the duration and intensity of a workout to arrive at a single score of the overall training load and physiological stress created by that workout.

One hour of functional threshold (as hard as you can go for one hour) = 60 Load index points.

**Physical work capacity**

PWC = power in watt at a given heart rate, named Physical Work Capacity

**Slope**

The slope of the black line in the heartrate power chart tells you how much your heart rate changes for each watt power-change. The more fit you are, the lower this number will be. When your aerobic capacity is better, it will take less effort to produce more watt.

**Strain factor**

The Strain factor (SF) is a calculated number that quantifies the intensity of a workout . It takes into account the adapted power (cycling) / adapted speed (running) of a workout in relation to your anaerobic threshold to arrive at a single score of the intensity created by that workout.

Unit: 0 - 1.3 units

**Zero position**

This is the point on the heart rate/power relationship chart where the best fit black line hits the heart rate axis (y-axis).

As your fitness improves, this number will decrease.

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