A question for Xerters. If I ride outdoors, and Xert records the activity as one with a certain focus and TSS, is that ride equivalent to an Xert indoor workout of the same focus and TSS in terms of gaining fitness for the intended purpose? I guess the question can be asked of two indoor Xert activities as well. Is there anything else, any other factor involved in producing fitness, fitness for the intended race, aside from focus and TSS? Are all Xert workouts of the same focus and TSS equivalent?
1 Like
We donāt use TSS 
But more or less, youāre correct. Assuming that the Focus values are similar & XSS is similar, then the two activities would have similar training effects.
Lets say that youāre comparing a weekly group ride thatās typically rated around 5-6 min power (Breakaway Specialist/Rouleur focus type). Youād be just as good to do that group ride (and have fun!) than to skip the group ride to go ride intervals by yourself for ātrainingā. Zwift races, group rides, etc. are training. I just think older methods are not as well-suited for rating the training strain (or difficulty) of unstructured rides/events, or at least adapting those efforts into part of a larger training scheme.
There is one additional thing I want to point out, however (mostly for the sake of discussion).
The best comparison for Focus duration to older methods that I could think of is IF (intensity factor, which if Iām not mistaken is activity NP/FTP). However, we go a step further beyond focus (which looks at the strain allocation across your 3 energy systems) and we look at what intensity you accumulated that strain.
For example, for a Focus duration of 6:00ā¦
- POLAR rating means that there were a few efforts above threshold power, but most of the strain was accumulated below threshold (think of a low intensity session with a handful of all-out sprintsā¦the focus duration might be very low, but the specificity is also very low)
- MIXED rating means exactly thatā¦ the ending focus may be relatively short, but there likely was a mix of efforts above and below TP.
- PURE rating means that a majority of the strain from that activity was accumulated near the target focus duration. i.e. Your ending focus was 6:00 and you had many efforts around your ~6min power.
From a theoretical training/coaching perspectiveā¦ as you approach an event, youād want the progression focus to approach the anticipated Focus of the event (i.e. progression focus reaches Puncheur for race with an anticipated ~4min focus). On top of that, youād also want the specific workouts to increase in specificity as well. For example, a PURE 4:00 focus workout would (in theory) be superior to a 4:00 POLAR workout when youāre in the peak/taper phases. Hopefully youāre following - this is some pretty high-level stuff 
2 Likes
Glad you added that bit re specificity as I think thatās a big difference. Iām sure mathematically thereās some equivalence but I would be surprised if the training adaptation is the same for polar vs pure rides, especially if some efforts are anaerobic vs aerobic. Am not sure that adding a couple of sprints to an endurance ride really trains your 6-minute power for example.
The other thing is difficulty - not that you necessarily want to train difficulty, but I expect there is a difference in adaptation (and recovery) between 60 min at 90 XSSR and 120 min at 45 XSSR (both all below threshold, so pure endurance)? Or between a 30 min threshold effort vs 5x6min threshold efforts with recoveries.
Similarly, riding outside for 3 hours and coasting / stopping for 10 min an hour vs riding continuously for 2.5 hours with no coasting is very different even if XSS is the sameā¦ I expect the latter would have a higher training benefit (and a higher difficulty score), and is more like an indoor session
Interesting. So as one approaches target date, I would assume Xert suggests activities that tend towards a āpureā specificity with regards to your chosen focus, right? I also notice thereās no way to search or filter activities based on specificity.
Not at this time. We calculate specificity, but itās not used as part of the XATA recommendations.
As Focus duration decreases (towards power sprinter) and specificity increases, the difficulty of the workout will also increase, since more time spend at/near the focus intensity = reduced MPA, increased fatigue & difficulty.
Yes, that makes sense, but that would only be true for workouts of a certain time length. In other words, a shorter workout of higher specificity could produce equal XSS as that of a longer workout of less specificity. Since XATA isnāt factoring in specificity, then the recommendation is biased towards length of workout, or at least total time for the week. Does that make sense? That seems to beg the question then, would a shorter workout of greater specificity result in greater performance in the target event? I donāt know enough about training to answer the question. It does occur to me that it might be desirable for XATA to factor in specificity in its recommendation.