Quantifying the "degree of difficulty" of a given erg session

[Sakly]

...
In combination with a belt, tracking of training could make sense, as data is absolutely reliable.

I tried tracking HRV data and resting HR data for 18 months using the H10 belt and EliteHRV. 3 minute reading first thing in the morning. I couldn't find any useful trends at all. The only time I saw significant movement was when sick or vaccinated where resting HR elevated. I gave up on it.

I use H10 OTW rowing, volleyball (wear belt, watch in the pocket), erging and cycling. Only use for the data I've found is when HR is unexpectedly high. Some days working really hard doesn't feel hard. It's good to know not to kill it the next day (if you believe in that training approach).

Same for me, tracked HRV with a similar app and the H10 over month. After my login wasn't working anymore (no idea why), I gave up on it, too. Also never saw useful trends or could derive anything training related from it.
The only thing as a trend I can see for me, when I have many hard trainings and/or much stress, my HR does not come down during the night so much. If rested and relaxed, HR goes down to low-mid 40s, otherwise only high 40s low 50s.

[Tobias Stoehr]

Has anyone out there (say, an exercise physiologist) ever developed a somewhat scientific way of defining how difficult a given workout was, preferably tailored to a specific person (so it would be based on your individual capability instead of an arbitrary scale).

I suppose you could try something based on time spent in various HR zones, where you get more credit (using non-linear factors?) for work in UT1 compared to UT2.

Or, if you knew you erg pace corresponding to VO2 max and FTP, you could use watts or pace and time in condition, without messing with HR.

I was just wondering, but it certainly could have practical applications as you develop an individual workout plan and look for ways to push yourself and improve your performance based on how your body is responding over time.

Yes, it has been done. Australian (rowing) physiologists have developed the T2-Minute concept, where any minute spent at a certain intensity is converted into (U)T2-minutes.
A similar concept is used on trainingpeaks (Training Stress Score, "TSS"), which I highly recommend for this. With a free account, missing only some premium planning and analysis features, you can connect to your concept2 logbook and sessions with stroke-for-stroke data, uploaded from ergdata or ergzone, are automatically transferred to trainingspeaks.

I think Polar gives a TRIMP score (training impulse) based on minutes spent at certain heartrates.

[mjhatten]

The measure I use for intensity is METS. METS are calculated by dividing your VO2 uptake (ml/wt(kg)/sec) for a given exercise by your VO2 uptake at rest (usually assumed to be 3.5 ml/kg/sec. The formula I use is Calories/minute x 200 / weight (kg) / 3.5 = METS. I set weekly goals for Met - minutes (METS x elapsed min) per week and compare them to HHS guidelines.

[Ombrax]

The formula I use is Calories/minute x 200 / weight (kg) / 3.5 = METS. I set weekly goals for Met - minutes (METS x elapsed min) per week and compare them to HHS guidelines.

Interesting. So actually, assuming either constant Cal / min, or avg Cal / min, then when you x by minutes to get Met - minutes, in reality time will cancel, and what you're actually using is Calories burned scaled by a constant (200 / (mass x 3.5) ).

[mjhatten]

Total calories is a measure of the total energy expenditure of an exercise. It does not really tell you your intensity, though, I use Met-minutes because it has a component that tells me how much work I did but also the intensity with which I did it. The final result may be the same but the factors are informative, too.

It all started for me with Physical Activity Guidelines from HHS. It not only describes the amount of exercise you must do but also the intensity at which you should do it. The introduced the MET-minute to me.

[Ombrax]

Total calories is a measure of the total energy expenditure of an exercise. It does not really tell you your intensity, though, I use Met-minutes because it has a component that tells me how much work I did but also the intensity with which I did it. The final result may be the same but the factors are informative, too.

It all started for me with Physical Activity Guidelines from HHS. It not only describes the amount of exercise you must do but also the intensity at which you should do it. The introduced the MET-minute to me.

Calories / minute is a type of measure of intensity, and if the equation you posted is correct:

Let K be a constant.

( Cal / min ) x min x K = Cal x K, so that's what MET-minutes is, essentially.

[mjhatten]

Calories per minute is a valid measure of intensity, for sure. I like the MET, though, because so much exercise research uses it as a kind of universal measure.

[mjhatten]

Using METS allows for comparisons between individuals without respect to weight differences. Calories per Minute for the same exercise between people of different weights would be different. METS would not because weight is part of the calculation.

The NASM formula I based my calculations on is: METS X 3.5 X BW (KG) / 200 = KCAL/MIN