There is a new achievement for when Intervals.icu thinks your threshold heart rate has gone up. You can click it to change your threshold HR (and other HR zones) for future activities. In this case I am not changing anything … I lost my only bottle in the first few minutes and got a bit thirsty!
The algorithm uses 98% of your best 20m HR or your best 60m HR, whichever is higher.
I understand the 98% of 20m note is something that is often seen in activities that push the boundaries, such as high intensity training or races. It seems the tool displays this calculated value to user in red font without changing anything under settings, but allows the user to manually use the new value (btw, where is the button that gets you this option - in your screenshot in the original post?).
Is it normal to see the computation suggest new thresholds that are lower than past activities that suggested higher thresholds? I find this odd. Does this happen only when the LTHR under settings is an undervalue?
If not, then maybe the red note should only be displayed when a genuine “global” high has been reached.
It should come up whenever it appears that your current set LTHR is too low. So if you ignore it and don’t make changes then it might show up with a lower number in future. It doesn’t change anything automatically because maybe you just ran out of water or something. I wouldn’t expect to see if often though.
Clicking the note should popup the dialog to update your HR zones.
No it was for myself. Too late, I set a new LTHR for indoor riding and re-calculated, all the red notes from old activities went away.
The root cause of this was setting an LTHR for cycling that was specific to outdoor conditions. Inside, ventilation and cooling is an issue. So LTHR must be set specific to indoor intensities. This is why I started seeing red notes appear within my Zwift races.
Although a distinction is made in Intervals.ICU between indoor and outdoor rides, I note that it uses only one LTHR value for both. A possible improvement area for future?
It would be a fair complication for athletes (and the system!) to have a separate set of HR training zones for indoor. Having separate indoor FTP was easier because the power zones are % of FTP based so I didn’t need another set of those.