Difficulty Calibrating HR-Based Workout Intensity

[Gabriel_Vargas]

I’ve been noticing some discrepancies when using HR-based workouts. Here’s one example: this athlete has a good correlation between Power Load and HR Load for completed activities. However, the planned workouts seem to be completely off.

A workout this week prescribed a narrow HR range at the top of Z2 and was estimated to have a load of 100. The athlete completed the session for the prescribed duration, but stayed in the lower part of Z2 instead… and the resulting HR Load was 130!

Based on the corresponding Power Load, I would say the issue is with the planned workout load, which is consistently much lower than the HR Load of the completed sessions. In other words, it seems that planned workouts are not using the same method to calculate load as completed activities.

The only way I’ve found to adjust the load of planned workouts is by changing the resting HR in Settings. However, for this athlete I’ve already adjusted it to values that are clearly unrealistic, and I’m still seeing compliance values around 140%.

Could someone help me understand what might be happening?

[R2Tom]

I think the workout builder is using HRSS, what’s the setting for the activity?

[Gabriel_Vargas]

We’re using Time in HR Zones

[R2Tom]

Here is the post about used method for workouts

Training load bug

I have just added support for calculating training load for HR based workouts using HRSS (normalised TRIMP). One hour at approx LTHR comes out at about 100 as you would expect. [Screen Shot 2020-07-20 at 06.43.20] If a step has power and HR then power is used to calculate load. If the workout has any steps with power then they should all have power to get an accurate load calculation.

And here are more details about HRSS

HRSS (normalized TRIMP) training load

You can now choose to estimate training load for activities with heart rate data only (no power) using HRSS (normalized TRIMP) as used in Elevate. You can also have different settings for cycling and running (and other sports). HRSS works better for running than the cycling derived models. You need to capture your resting HR and a good threshold HR for HRSS to work well. HRSS is now the default model if there isn’t enough data to build the others. [Screen Shot 2020-03-21 at 11.14.39] This cha…

HRSS may can have a better correlation to power load, I use it myself, and power and hr load are pretty close to each other for me.

[Gabriel_Vargas]

Thanks a lot, @R2Tom

I actually used HRSS from the beginning, but recently I ran a few experiments and found that Time in HR Zones correlated much better with Power Load (at least over here), making things much easier on my end. I’m not entirely sure why.

I’ll mark this as solved, but the current behavior feels a bit messy. If there are three different HR load methods available, then it seems the Workout Builder should automatically use whichever HR Training Load method is selected.

I’ll try to bring @david’s attention to this, although I’m not sure whether this should be considered a bug, an oversight, or a feature request.

[Gerald]

If you take some basic principles:

1. 1h at 100% LTHR is 100 (load).
2. 1h at 100% of FTP is 100.
3. 1h at 70% of FTP is 49.
4. 1h at 70% of LTHR is 27

The 27 doesn’t make sense, but I don’t really know enough to know why.

All by MTB and gravel rides prior to March this year are based on HR (for load).
I checked one ride that was an hour at 69% intensity. It shows 30 (HRSS) and 45 (Tiz).
TrainingPeaks shows 39 hrTSS

[Gabriel_Vargas]

Yes, but the scales are different between power and HR. A Z2 ride may correspond to around 70% of FTP, but that probably translates to something like 78% of LTHR.

What I did was switch to Time in HR Zones because the resulting load aligns much more closely with Power Load. That makes things much easier when I need to communicate the training plan to nutritionists, for example, or when I want to show an athlete the expected load for a training block. This is particularly important because I rely a lot on HR to prescribe endurance rides, even for athletes who have power meters.

So it seems that the ideal solution would be for the Workout Builder to use whichever HR load formula is selected in Settings.

More generally, I feel that HR-related features are somewhat overlooked in Intervals.