The Seasonal tab enables you to see how much time you spend in each heart rate zone by Year/Quarter. The heart rate zones are estimated adaptively and change in line with your prevailing fitness. This report has been in place for a long time. What is new is that you can now break it down by Sport.
Sport defaults to TOTAL, and so long as this is selected the report is unchanged from how it has always been:

However you now pick a single sport from all of those that you have recorded on Strava for which you have heart rate data:

This will then show you the time that you’ve spent in each heart rate zone for that Sport. You may see that there are fewer Quarters showing if you only occasional engage in that sport or if you often don’t use a heart rate monitor for it.
This new feature gives you the ability to see the differences in the nature of your training effort across different sports. For example, you can isolate and compare Rides or Runs and ensure that the amount of Zone 1 time shown on the charts doesn’t include any time you spent doing Yoga or Walking.
(Note that this tab also still has controls to select a Date range and a Group but these have no effect on this report.)
Please can you confirm how I access my details- thank you
Hi Jo, The process for getting going on Crickles is described here – https://cricklesorg.wordpress.com/2019/07/01/joining-crickles/. You’ll need your Strava ID and this tells you how to find it – https://support.strava.com/hc/en-us/articles/216928797-Where-do-I-find-my-Strava-ID-. If you have any problems please do send me an email (ian@crickles.org). All the best, Ian