I don't understand the TSS calculation on Suunto

[Lionel B]

Hello,

I’m a new suunto user since last june.
I’ve been diving into the watch and the app parameters and now trying to understand how TSS works in Suunto (if it really works ).
I’ve been reading nice article on how calculation is made here : https://www.suunto.com/fr-fr/sports/News-Articles-container-page/training-with-tss-and-hrtss/

But there is some issues about that.
First thing, about cycling.
As you can see in the TSS formula, we use FTP to calculate it. But as expressed on the folowing forum threads, you can never set your ftp, neither it is calculated anywhere. How is it possible to use TSS without using FTP ? That is a really weird choice from Suunto, or am i missing something ?
2 threads about that :
https://forum.suunto.com/post/102823
https://forum.suunto.com/post/92089

That said, my TSS score when in use my home trainer is not accurate. Sad.

Second thing, about hiking/running/trailing.
You can use different formulas to estimate your TSS. But Suunto offers me really weird estimations.

First example
I have an 7h bike activity (imported) with big pause (52min riding in total, with 97% heartrate zone 1)
Real TSS should be between 25 and 50, but Suunto offers me :

• 286 TSS (hr) : i guess the algorithm don’t like the big pause
• 980 TSS (MET) : this is ridiculous, how come you can offer such a high level of TSS for a zone 1 ride (even 7h)

second example
I’m trying to compare

• one hike : 7h, 27km, 2000d+, average heart rate in zone1
• one trail : 6h40, 40km, 2700d+, average HR zone 3
  TSS (hr) will be 474 for the first and 538 for the second
  Difference looks really strange to me. It looks ok for the trail, but the one for the hike looks totally overstimated. Strange.

So overall, TSS on suunto looks interesting, but there is some questions/bugs/unfinished features which leaves them
But maybe you have some explanations

[isazi]

@Lionel-B threshold should be the first value of Z5 (HR, pace, power) in your custom zones

[Lionel B]

@isazi how do you convert a HR value (threashold) in a power value ? (FTP)

[isazi]

@Lionel-B you don’t, you need to do the proper tests and set zones for the different metrics. But if you use TSS (power) for cycling just setting the power zone is enough for TSS (other metrics in the app may get confused if the HR zone is much different, but not TSS)

[Lionel B]

@isazi but how do you set the power zones ?
I havn’t found any options in the app or the watch to do that

[isazi]

@Lionel-B https://www.suunto.com/en-nl/Support/Product-support/suunto_race_s/suunto_race_s/recording-an-exercise/intensity-zones/

[Desdinova]

@isazi Hi both sorry to butt in here, but this is how I set my running power zones - just wondering if this looks right as the results look ok,

I did the LT test SuuntoPlus to get my HR and Pace threshold, I then took the average power from the last two 10 minute sections of my LT test and used that as running FTP in intervals.icu to get that to define my power zones, and back-tracked thiose zone values into Suunto.

Now the power zone times seem to match my runing and pace zone times in runs…

Is that the way? I ask as although there was a lot of info on pace and hr zones, there’s less on Power zones and so I’m well aware this method may not be optimal…

[isazi]

@Desdinova I do the same (except intervals.icu, I use training peaks for that)

[Lionel B]

@isazi said in I don't understand the TSS calculation on Suunto:

@Lionel-B https://www.suunto.com/en-nl/Support/Product-support/suunto_race_s/suunto_race_s/recording-an-exercise/intensity-zones/

Oh i got it ! Missed that option before

[Desdinova]

@isazi I cant believe i did something right Must be my birthday lol

Seriously though, thanks for the info…

[isazi]

@Desdinova there are plenty of fitness tests that can help you define your thresholds and zones, just pick one that lets you train at an effort level that matches your perception

[Desdinova]

@isazi I was comfortable with the pace and HR side, just theres less info on power on line so I did wing it a bit

Thanks

[jussim]

No one at Suunto thought that it’s peculiar that a user has to use external calculators? Let us at least have one in the app. Of course the best option would be that you are able to set up your zones in the app too or at the very least there’d be an option to do it automatically for you after using Anaerobic Threshold app but that might be asking for the moon.

[The_77]

@jussim the moon was briefly in the previous Android beta

[althaea35]

@The_77 https://forum.suunto.com/post/150727

Is this what you are referring to?

Looking forward to it!

[Elipsus]

@Lionel-B For your first example, TSS (MET) means Metabolic equivalent of Task, so it doesn’t take into consideration anything execpt duration and type of activity, each sport profile has a MET value, that gets integrated over time, so in this case Zone 1 / Zone 5 doesn’t have any incidence on the final value

The fact that your bike activity is imported also maybe wreak havoc on the alogtithm calculation for the TSS hr ?

[Mff73]

@Elipsus said in I don't understand the TSS calculation on Suunto:

The fact that your bike activity is imported also maybe wreak havoc on the alogtithm calculation for the TSS hr ?

imported activities doesn’t have the proper HR zones, they have default HR zones in Suuntoapp. --> for sure “wrong” tss calculation, if calculated. If TSS value is in the fit file, it may work though

[Lionel B]

Ok i’m back with two activities which are not imported

first activity : trail
13.6km 400D+ average HR 142 (1h25)
TSS (hr) is 83

second activty : hike
12.6km 400D+ average HR 110 (2h15)
TSS (hr) is 87

Do you think it is normal ? i do not.
if we base TSS on heartrate, and according to the average HR for each activity, i would consider the first activity would have a much bigger TSS

what do you think ?

[SvenSchroeter]

@Lionel-B - I have seen something similar. In my case, the HIKE is being measured against the default HR zones. And the TRAIL RUN is using the custom running HR profile / Pace Profile / Power Profile. Depends on how you have setup the watch.

[The_77]

@Lionel-B if you look at it another way, TSS is a measure of your % effort of your FTP/hour, i.e. if you did FTP for an hour it would be 100 TSS (from memory). In the first activity you averaged 58.5 TSS/hour. Activity two, you averaged 38.7 TSS/hour. Clearly activity one was much harder, just activity two took longer, and Suunto is only working off your Z4/Z5 interval for TSS calcs.

All that said, sometimes I feel walking/hiking feels like it gives higher TSS than makes sense, but I understand why it does.