The Seasonal tab has now been re-introduced to the Navigator. Now it shows you your time in each heart rate zone for each of the last eight Quarters (subject to your Strava history going back that far). This enables you to see whether you really were base building over the winter and adding intensity in the early season – or doing whatever your training plan called for. It also makes it easy to compare your quarter-by-quarter efforts with those from a year ago.
The definition of the zones (Z1 to Z5c) are essentially the same as those defined by Joe Friel in articles that can be found online. The main difference from those and similar methodologies is that the Crickles estimate of your Lactate Threshold Heart Rate (LTHR) is calculated adaptively from your Strava data and applied consistently.
You’ll also notice that we have reverted to a light colour scheme for the Navigator and Crickles Charts. The Activities table on the Navigator works much better this way, and sometimes it’s just good to have a change.