FAQ ~ TSS & IF Discrepancies
Norway's Ronnie Rohne
working with his team-mate on the front
to breakaway at FTP + output in a post
Birkenbeinerritter event
In your programme you give TSS (Training Stress Scores) and IF (Intensity Factor) numbers, but these differ to my software numbers at the end of the session.
Also, my power and heart zones come out different! Which ones are right and what should I do?
Ronnie Rohne ~ NorwayAnother of our "most asked questions" from riders with power meters.
All TSS, IF, CTL (Chronic Training Load) and ATL (Acute Training Load) numbers are relative to your FTP (Functional Threshold Power). Wow, that's a lot of TLA's (Three Letter Acronyms) in one sentence!
the number this question relates to, is the red "75" above
In all our programmes we say IGNORE THE NUMBERS for a very good reason. Most numbers I see are "wrong".
Follow the programme, by riding to the best of your ability for each session, and you WILL end up with a constantly rising, predictable, sustainable, fatigue-managed, fitness profile like the one below...
The numbers will be what they will be. If you've done your best, whatever they end up as they will be right. But you need to do some regression analysis to check that your original FTP premise was correct.
False Premise
The problem with most "training programmes" is that the whole of the
programme, and the sessions within, are constructed on a false
premise.
The starting point for most programmes is usually a Performance Test, or a ride's power analysis that elicits an extrapolated FTP number.
That number ends up finding itself in the programme, as the perceived defining parameter for the training zones and power outputs for the subsequent eight to twelve weeks.
What if that number is wrong? What if the rider had an extraordinary day to bang out an output they could not repeat? What if they had a poor day, when they "under-performed" due to fatigue, impending illness, or just weren't in the "head zone" to do their best suffering on the day?
If the potential forty-eight sessions of the programme that follow are based on that one test (or ride), then the chances of the numbers relating to those sessions being accurate over the next two to three months are, to say the least, remote at best.
Here is one of our riders' 20 minute profiles over an extended period. Most of the efforts fall in to the 300-320 watt range. But you can bet your bottom dollar, that (left to their own devices) the rider would report (to put in the programme) that their peak 20 minute power is 340 watts!
Which would cause all their subsequent TSS & IF numbers to "under-read".
work on averages and trends, not peaks and troughs
The Scores
If your FTP is taken from a "dubious" test (or on a climb), your TSS, IF, CTL, and
all other dependent metrics will also be dubious in their accuracy.
How can they not be?
If your FTP is taken from a "bang-on" test, then your scores will be accurate, at best, for a month or so.
If the programme is working as it should, the scores will ultimately move out of kilter! If they don't, again, something is wrong.
All our programmes will, to some extent or another, improve your FTP? If your FTP isn't regularly updated within your software as you progress, the TSS and IF numbers will slip out of alignment.
But it's just a number, you still did the session, you still did your best and you have still progressed. A watt is a watt; so whatever the wattage is, it's right. The TSS and IF though, may not be.
Listen to your body and the numbers will look after themselves.
The Zones
As we've said in other areas
of the website, and in the training programmes,
THERE ARE NO DISTINCT Training ZONES.
You do not go from 200 watts being Tempo to 201 watts being Lactate
Threshold. The fact that Lactate Threshold is also a myth, is
covered elsewhere!
It will be the same in Strava, WKO, Training Peaks, Golden Cheetah or any of the other programmes you use to track your fitness.
If the "expected physiological outcome" of the session is Zone 4 and you have Zone 5, this could happen by just being one watt or one heartbeat above the "zone" within your software.
Never take these numbers at face value, always scratch beneath the surface and always "triangulate" all information. Always...
Take the average wattage of your sessions over a month and use your judgement and experience to give you an "in the moment" FTP figure. The more information you have, the better clarity you can give to your decision making and outcomes.
To Clarify
TSS and all the other measurement metrics are drawn from your
FTP. If your FTP is inaccurate, then everything that feeds
from it will be.
In theory, there is no difference between theory and practice. However, in practice you will find there is a world of difference...
The accuracy of the FTP number within your programme is paramount to the numbers being "right". But it has nothing to do with the success of the programme.
And as for heart rate numbers and zones being out of kilter,
here's why...
