Training Difficulty

I’m trying to find a solution of how to select the appropriate workout difficulty (for me and my wife respectively). The classification that Trainerroad uses seems to be not too bad to categorize a workout in a given type, however I’d like to come up with something that I can use myself directly from a workout - maybe even a number that could be displayed in my workout library.

What comes to mind is of course TSS, but then this doesn’t really reflect the real difficulty of a workout. I guess the reason is, that TSS does not account (enough) for work under fatigue. The TSS is the same for these simple workouts:
-60m ramp 120-70%
-60m ramp 70-120%
-60m 98%

All three come in slightly below 100 TSS but even though the last one is very, very hard it can theoretically be achieved, which I doubt for the first two. It probably gets even worse, when doing intervals. Doing on/offs 30s 140% / 30s 40% has an intensity close to 1 but is clearly another level. Even 15m 140% and then 45m 40% come in with an intensity below 1. I guess you get the point.

So what I’m looking for is a measure that tells me how hard a workout is, so when I plan the following week(s) I can look at the last workout of a given type and see how I felt about it. Let’s say I had an RPE of 9 for a given WO it would make sense to take one with a similar value, if I want to go again similarly deep. Going to a considerable higher value would suggest of course that I probably will not be able to finish that one, so it doesn’t make sense to plan it. A considerably lower value would suggest that the workout is too easy and will not contribute much to progress.

I understand that such a metric cannot be used over all workout-types (i.e. Sweet Spot vs. VO2max) and it doesn’t make sense to go always for what’s barely achievable. But these parts can be factored in by designing the plan for the week(s).

How much do you know about progression?

Example:
Tempo/SweetSpot
30-90 minutes across a number of intervals.

Threshold progression:
3-6x 8-min intervals

VO2 progression (max possible, but sustainable, power across all intervals)
3-6x 3-4min intervals

Well, Gerald, I think that’s exactly the point that I’m heading for. At the end we improve by progressive overload - and sure you can do it by taking last week’s workout and make it a bit more difficult.

The point however is, that you can change a lot of variables to do that, and that things get hard to compare. To make the workout more difficult I can:

  • Increase the %FTP of one or more intervals
  • Increase the duration of the intervals
  • Increase the number of intervals
  • Increase the number of interval sets
  • Shorten the recovery within an interval set
  • Shorten the recovery between intervals sets
  • Increase the time of the workout

… and there are clearly more possibilities, than these. Now the point is, how do they compare.

TSS is obviously an indicator but probably not good enough. I looked at Xert’s XSS which seems to be a better indicator, not sure if it’s good enough though.

As I mentioned Trainerroad has a system where they assign a difficulty value (“Workout Level”) to each workout within a type. Look at the following picture, in theory these workouts are all of the same level of difficulty even though they have a completely different structure and total time.

So what I’m looking for is a metric to mimic this concept and make different workouts comparable to prescribe them correctly and make use of the progressive overload even if workouts are different in structure.

And to give you an idea what I mean that TSS is not a good measure. Compare these two workouts:
image
image

From a TSS point of view the first one seems a lot harder, even though the time with high load is exactly the same. Sure it’s longer but that is due to longer recoveries which won’t add a lot of strain. XSS in comparison is 87 for the first and 83 for the second, which is better than the 83/66 but still it has the first workout more difficult. When I put them into Trainerroad it comes up with the following


That seems a lot more to the point giving the one with the longer recoveries a much lower difficulty level.

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Normalized Power is very good indicator.

This article is from TrainingPeaks.

Normalized Power is calculated using an algorithm that is a little complex, but in a nutshell takes into account the variance between a steady workout and a fluctuating workout. The resulting value is an attempt to better quantify the physiological “cost” of the harder “feel” of the variable effort. For a highly variable workout, NP can be much higher than average power, where for a very steady workout, NP and average power are equivalent or very close together. A relatively high NP is showing that the workout had a lot of variation, and was harder physiologically than what average power may reveal.

Looks like your idea of ‘difficulty’ is very much (exclusively?) oriented towards intensity.
You should be paying more attention to increasing duration at lower sustainable intensities.
Any workout with an Intensity Factor above 0.9 is hard and due to the fact that it is hard, TSS from such a workout will rarely go far beyond 100. On top of that, it will not be repeatable the next day because recovery is not sufficient.
If you do longer lower intensities, TSS can go really high (500 and higher), on the condition that your aerobic fitness is able to cope with that. Recovery from those lower intensities is far easier and makes them much more repeatable.
Do most of your work at lower intensities to build aerobic fitness and stamina. Add 1 or 2 hard sessions a week where you either increase the time/n° of intervals when you want to improve repeatability/recovery at that intensity, or intensity when you want to increase single shot at that duration. Do one specific zone during a multiple week period, then switch to another hard zone. Example: four weeks of hard sessions at VO2max followed by four weeks at Threshold. Don’t constantly mix all those intensities, give your body the time to adapt in a specific metabolic zone, then target another metabolic zone. Switch back and forth if you want, just don’t mix them.
Chasing PB’s week after week will result in one or more of the following:

  • plateauing
  • non-functional overreaching
  • over-use injury
  • overtraining

That’s reflected in IF, which is calculated with NP.

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Thanks for the input.

I don’t think that intensity is the only or even the main driver. I just selected some bold examples to demonstrate what I’m looking for. Neither of the examples are real world. You can see there’s not even warm up or cool down with them.

If it were intensity then IF would be the metric - but it clearly is not. If you look at the screenshot from Trainerroad with the 5 different Threshold workouts they have IF between 0.8 and 0.91 and still come in as similarly difficult. Neither is it TSS which ranges from 81 to 129.

Currently I’m trying to mix things up a bit - especially I’ll try to put in some Z2 each week no matter if I did Sweet Spot, Threshold or VO2max. But I’ll think about the approach of addressing only one energy system at a time.

But besides that, I’m simply looking for a metric to compare workout difficulty in the way described. Even if I switch to the approach of addressing only one energy system at a time it makes sense to understand how ‘hard’ a workout will be compared to another one. I might want to do a 2 hr tempo ride on the weekend and two 1 hr Sweet Spot rides within the same week, but I’d need to know how difficult they will be to make an educated choice, so they are reasonably challenging (not too easy, not too difficult) to promote the targeted energy system and still have a variety within the workout layout.

I just read this quote which says it all:

Do Work

With these workouts, the name of the game is “work over time.” These sessions should not create strain in your program. Strain defined as recovery that takes more than one day.

  • With the Green Zone sets, recovery should be overnight.
  • With the Tempo sets, recovery should be sufficient if a Green Zone day follows.

If more recovery, than the above, is required then the dose and/or target was set too high.

Adapt this to the training time/frequency you have available and you will go a long way. The load, in terms of intensity/duration, of each training session should be adapted in such a way that you are sufficiently recovered to perform well on the next training session.
That’s the most efficient way to progress. Do enough each session to improve, but don’t overdo because that will reduce effectiveness of your next session. Increase work in a sustainable way. The amount of work done has been proven to be the primary factor of performance improvement. The better you get at balancing ‘which’ work, the faster you will improve.

Correct. TSS is a terrible measure. Anything above threshold doesn’t get weighted correctly. 7 x 10s sprints or an hour in the middle of Z2 get basically the same TSS. Ridiculous.

Anything under OBLA is pretty easily weighted by TSS but once you go over that threshold it becomes a joke really.

TSS, no more than FTP is a bit of a nonsense I think. At the end of the day, you can’t but an number of all the physiological effects of a training session and your reaction to same.

Something else that comes to mind:
The difficulty of a specific workout will very much depend on what you did the day(s) before. You can’t do the same VO2max workout for several consecutive days. I’m afraid that the ‘difficulty’ metric you’re after is something very complex.

That’s clear, but for simplicity I’d let that be factored in by the person creating the plan. The metric could be based on the assumption that the person doing the WO is well rested. So if prescribing VO2max on two consecutive days, this would mean to need to take a lower value for the second day - however, I personally would not go down that lane. In my understanding this would mean to set an impulse when supercompensation is not complete and you’d either start on a too low basis to improve (on the classic supercompensation model) or looking at it from another perspective the training would not be in the optimal range for the targeted energy system.

I understand it’s pretty difficult - otherwise it would have been around for some time - but as said, Trainerroad has obviously created a model, so there’s probably a way to do it with formulas.

It has to be something that takes time at a given intensity (depletion of W’ is not enough as SweetSpot takes its toll as well), recovery time (maybe based on LTP) and total time.

I’m always look the IF.

Exactly. Which is why TSS is garbage. It doesn’t actually measure or represent training stress

It all depends what you are training for, which is where specificity comes into the training you do.

Yes and No. I got your point that TSS is by nature flawed, and I kind of agree.

The point is, TSS is a number to measure effort, and as you said, effort is pretty hard to measure, plus is very personal.

Even though it isn’t perfect, it’s the best tool available. Just use it with a grain of salt and add it to your RPE, and not blindly use it.

It appears to me that you want to figure out how Trainer Roads A.I.calculates multiple facets of difficulty within a training program ,block of training , weekly , and within a workout . TR uses tss, Intensity factor, FTP , calories ,progression levels , time in zone ,rest periods all in a way that chooses the next workout for you . The options seem to be pretty endless and all basically rely and depend on how well you responded to your last weeks workouts . Why not just let them do it for you ?

I rather would say, I’m trying to find a solution that solves a similar purpose. For workout levels TR however clearly does not use any values that are not directly part of the workout itself, they do this for the selection of the WO only - based on the workout level. I think that Difficulty at XERT is another concept that tries to do the same, maybe even more reliably.

So why do I not let them do the work for me?

When I read they’re using AI to determine my plan and especially next workout I expected they really have a close look at what I’m doing, but after doing a deeper research I found out, they only do it for trainingsessions that include their workouts (they say themselves somewhere in the documentation, that they think about implementing that). So it’s pretty useless when you do other things as well, and you want and automated suggestion. It is a great concept, however.

So I like my Z2 rather as a Robopacer ride at Zwift than a boring WO; I want to ride regularly races on Zwift; when I’m outside I choose a route not a WO. All this said I understand that this is not the perfect trainings regime, but then the best trainings regime is the one that keeps you training.

So the answer to the question: Why do I not let them do the work? Because I’d like to do it on my own, I’d like to have my WO library and a number assigned that tells me how WO fits into my wifes or my abilities to finish it. Will it be easy (when I’m tired) or a stretch (when I’m feeling like I want to try it).

From what i understand TR can use your outdoor rides in consideration for ftp scoring . It also has a train now feature and will recommend a workout for you daily . Train now gives three types of workouts with a “recommended “ workout based on your previous training .

TR uses so called Progression Levels to suggest a WO. These are adapted whenever you do a Trainerroad WO. They do not adjust for free rides.

The train now feature suggests 3 WOs (one Z2 or Tempo, one Sweet Spot or Threshold and one VO2max or Anaerobic). As far as I understood this is based on the results of past WOs (ie progression levels), and looks at training load as well.

So as said I think it’s a good concept. It simply is not thought to the end or rather does not use its full potential; or maybe I have to choose a different approach.