Hi David,
Would you consider adding Heart Rate Reserve (%HRR / Karvonen) as a native option for calculating the standard heart-rate training zones?
Garmin, for example, allows HR zones to be based on:
- % Max HR
- % HRR
- % LTHR
I currently use Garmin’s 5-zone %HRR system with:
Max HR: 185 bpm
Resting HR: 49 bpm
This gives me:
Z1: 117–130 bpm
Z2: 131–143 bpm
Z3: 144–157 bpm
Z4: 158–170 bpm
Z5: 171–185 bpm
I can manually reproduce these boundaries in Intervals.icu, which works, but they are effectively entered as percentages of LTHR rather than being calculated from HRR.
The Karvonen calculation is:
Target HR = Resting HR + (% × (Max HR − Resting HR))
A native option such as “HR zones based on: %HRR” would therefore be very useful, especially since Intervals.icu already stores Max HR and resting-HR data.
One advantage would be that athletes whose resting HR changes significantly as fitness improves could update their HRR zones without manually recalculating all of the boundaries.
I don’t necessarily think the zones should automatically change every day with normal daily resting-HR fluctuations. Perhaps the user could choose a fixed resting HR, a longer-term resting-HR value, or manually trigger an update.
A second, smaller suggestion: it would be useful if the lowest standard HR zone could have a configurable lower boundary. At present Z1 starts at 0 bpm. In my example, Garmin Z1 is 117–130 bpm. This isn’t particularly important for training, but it would make time-in-zone reporting between platforms more consistent.
My practical reason for requesting this became very obvious today. I completed a 60-minute elliptical workout targeting Garmin Z2. Garmin recorded 54:30 (90%) in Z2, with an average HR of 136 bpm. With my previous Intervals.icu LTHR-based zones, almost the entire workout was classified below Z2.
I have now manually changed Intervals.icu to match my Garmin HRR zones, so there is a workaround. But native %HRR/Karvonen support would make this much easier and would keep the calculation methodology consistent between Garmin and Intervals.icu.
Thanks for considering it — and thanks for all the continued development of Intervals.icu.
