LTHR from Sufferfest 4DP test too low?

Training
1

I’m fairly new to cycling in general (10-11 months in) and to training, but from what I understand my max heart rate is relatively low. I recently completed a 4DP test on Sufferfest which has given me an LTHR of 141. During that test I recorded a max heart rate of 166. The next day I did a workout “A Very Dark Place” and also saw a max heartrate of 166. I am recording my heartrate through a Wahoo Tickr. Both workouts had me close to total exhaustion, with very little left in the tank.

The issue is that if I take the 141 LTHR from the 4DP test and enter it into the Intervals.icu Heart Rate Training Zones it calculates a max of 155. It also makes the zones in general very tightly clustered:
image

My question is: Am I doing something wrong, or is my heart rate just unusual and causing problems with the usual “rule of thumb” calculators?

2

Hmm. I actually don’t know enough about this or how The Sufferfest estimates LTHR to properly answer your question. I implemented Joe Friel’s calculation using LTHR because the zones match up nicely with cycling zones (for me anyway). You could try fiddling the LTHR value so the max comes out at your actual max.

If you also have a power meter you can compare. Riding in Z2 on power should generally have you in Z2 on HR (after a bit of riding anyway).

3

What if you took your Ave HR from the last 15 mins of the 20 min portion of the 4DP test? Does that seem more reasonable?

4

Only marginally: That was 145. Which gives a max of 159. I wonder if it was a flawed test, and I should have gone harder on the 5 minute interval earlier on which meant I wasn’t as fatigued for the 20min effort as I should have been.

I guess I could work backwards and input a LTHR of 151 which gives a more believable 166 max HR.

5

You want the max HR to be correct as Intervals.icu uses that to detect and fix HR spikes on rides.

6

All sorted. Did a new test on Sufferfest which gave me an LTHR of 157, plugged that in to the HR Zone model and it falls out as 173 max HR, which is probably not too far off.

1 Like
7

Just out of curiosity: at which part of the 4DP test did you reach your max HR? Before checking mine I was sure it would reside at the end of the 5min MAP interval. However, in fact I reached my max at the end of the 20min FTP section. MAP, FTP and AC were all very close to each other regarding max heart rate.

8

On the 4DP test, my highest HR was at the end of the 1min! (166). Quite a bit higher than end of the 20min, where it was 157 for the last 2 minutes.

On the Half-Monty it also hit 166 for the last 30 seconds of the ramp test.

9

I’m also a Sufferfest athlete. My last 4DP generated a max HR at the end of the 5 min MAP (174 bpm). It predicts my LTHR as 164 bpm. HR at the end of the 20 min MAP was 169 bpm.