Heart rate is displayed as a bar colored by your personal heart rate zones. The default scale of the heart rate graph field is FTHR+10%.
|HEART RATE ZONE COLORS|
*Stages default heart rate includes 6 zones, but more can be added when zones are customized in the Stages Cycling app.
FTHR is shown on the graph as a dotted line. If heart rate exceeds FTHR+10% the graph will adjust scale to match the max value in the current span.
When that value is no longer displayed, as graphing data is replaced in a fixed span, the graph will readjust its scale to return to either the max heart rate value or to FTHR+10%.