Running TSS - Power based, need option to set FTP

[herlas]

Right now TSS calculation for power-based runs is looking at the high end of power zone 4 or low end of power zone 5 however you like to see it, to set the runner’s FTP (Functional Threshold Power) value, which is a metric that’s in use to determine our TSS.

By definition FTP is the best effort in average watts a runner can hold for 60 mins straight (bet most know that already )

Have seen the formula behind calculation for TSS, which is described here https://www.trainingpeaks.com/learn/articles/estimating-training-stress-score-tss

Which is

TSS = (sec x NP x IF)/(FTP x 3600) x 100

…where

“sec” is duration of the workout in seconds,
“NP” is Normalized Power (don’t worry about this for now),
“IF” is Intensity Factor (a percentage of your FTP; in other words how intense the effort was),
“FTP” is Functional Threshold Power (your best average power for a one-hour race or test),
and “3600” is the number of seconds in an hour.

Also verified TP is indeed using it to calculate our TSS scores when running with power.
Issue I’m trying to describe here is that, at least in my case and many I suppose, our TFP is not always equal or close to what our watch is picking it to be (upper level of zone 4/ or lower of zone 5), so I’ve seen the effect of this to be lower TSS scores in Watch/SA as compared to TP where I have a field to set my FTP.

I use Stryd, it gives me an estimation of what my TFP is and I use that in TP, and my power-based TSS for running are always underestimated in the watch and SA (as it’s using a higher value for FTP, which isn’t right)

so I guess the request here is to be able to set FTP in watch/and or in SA, so that we can get the right TSS that’s more aligned to our effort in each workout, and ultimately match what’s in TP.

Trust me, it makes a big big difference when you’re seeing the correct TSS scores, basically I went from Maintaining Fitness to Productive Training by just making sure SA has the right values, (manually updated last 42 days ) , and it pictures better how I feel about my training.

Thinking… maybe current way power-based TSS is calculated was probably a first iteration of TSS and watch is set to include this much needed feature of setting your FTP value?

If this needs to be moved to feature suggestions, please do so

Thoughts?
Thanks

edit: Adding TP screenshots of my TSS scores for a hard effort track workout(intervals) I did recently, blue arrow is TSS is given when using TFP as high end of power zone 4, and the green one is using the estimated TFP from Stryd as FTP in TP, in this case a 17 TSS point difference, which is a lot, and have had others varying for more than 20 points too.

[Bulkan]

I get it, I suppose what we need to know is how is calculating the TSS if there is not a FTP in running or cycling.

I think is the upper of zone 4 limit but you are saying that setting the zones like that is not giving you the right tss, aren’t you?

I have my zones with old FTP I’m going to update the zones and see if the tss℗ is the same in both platforms. (All variables have to be in the same data: weight, pulse…)

[isazi]

@bulkan if you set the same FTP it computed the same TSS. What @herlas is saying is that the FTP Suunto uses is not the FTP Stryd provides, and cannot be configured, so you get different results for TSS.

[herlas]

@bulkan I think we know what watch uses as FTP as I said, zone 4 upper limit that is, play with TP and this formula in excel, TSS = (sec x NP x IF)/(FTP x 3600) x 100, TP gives you NP (normalized power) which is the avg power of a run adjusted for the variability of power in that run (e.g intervals o hilly terrain make NP grow), use the top Z4 value you have in your power zones in the watch as FTP and you can get the TSS value watch is currently giving you after each run. IF metric is defined as NP/FTP.

[herlas]

@isazi that’s another way to see it I guess, stryd FTP (CP in stryd terms) is given as upper value of zone 3 (threshold zone) and watch uses upper zone 4 value,either way, this isn’t tied to Stryd, you can do field tests to get FTP in running, there are different methods available and it’ll be crazy to think it’ll match Z4 upper value as in our Suunto watches for everyone if any.
Let me reinforce, issue is not about power zones between stryd and Suunto watches, it’s what’s being used as FTP in our Suunto watches and the request is to have way to set FTP in the watch/SA or both I guess

Thx

[herlas]

Adding to it, FTP is not a static metric, if you train to improve fitness in running, you’ll most like raise your FTP up(ability to hold higher power during an hour) and the same applies for when you’re injured or stopped training for any reason, FTP will be decreased, this is not like HR threshold that stays pretty much the same for a long time.