Often, athletes will perform activities but without a power meter.  Sometimes these come from commutes, or using second bikes without a power meter.  Sometimes you’re on a trip and rent a bike.  In these cases, be sure to wear a heart rate monitor and preferably also use a cadence sensor.  When this feature is enabled, the system will attempt to estimate various important metrics:

Heart-rate Derived Metrics (or HRDM) works by first analyzing your historical data to detect the patterns that exist in your data between power, heart-rate and cadence.  Then, after determining this relationship, any activity that has heart-rate or heart-rate and cadence will be analyzed.  Using a cadence sensor together with heart-rate is better than just using heart-rate as they can be combined to estimate your level of fatigue, when you are stopped, slowing down and accelerating in order to derive reasonable estimates of all the metrics above.

Note that the metrics are only evaluated with heart rate for activities that do not contain power data.  If an activity contains power data, no heart rate or cadence data is used to derive the metrics since power can be used directly.

To fine-tune the algorithm to better reflect your current resting and maximum heart rate values, disable Auto-estimate Heart Rate parameters and key in your resting and maximum heart rate values directly.