TS (Training score), TSS (training stress score) explained?

I am not a good cyclist who tries to improve. I am a beginner who likes to play games. :slight_smile:

Trainingpeaks, Trainerroad and all of the CTL, TS, TSS, fitness, freshness etc jargon is foreign to me.
I tried googling it and learn, but I have found contradicting answers (e.g. FTP is for maximum effort for 20 minutes, it is for max effort for 1 hour, etc.) and most of the answers make sense if you are using those products, but they are alien to me out of context.

For some reason Zwift uses the TS metric.
I tried to retro-engineer it back, and sure enough 1 hour on my FTP is 100 TS, so less watts for less time is proportionally less TS.

So my question is:
The “magical number” is 150? Which means that my body should fully recover for the next day if my total TS for that day is less than that? Or how does this work?

No. Not all TSS is created equal.

You could get 150 TSS from a 3 hr steady endurance ride at about 70% of FTP.

You could also get 150 TSS from 90 minutes of VO2 Max intervals.

The former you could probably do for six days a week, take Monday off, and repeat for the rest of your life.

The latter … maybe you’d last until the first Thursday.



I think Zwift’s TSS metric is similar (if not actually based upon) Andrew Coggan’s.

Coggan’s (TSS) Training Stress Score® is a way of measuring how much stress is put on the body from a ride. TSS® is calculated using Normalized Power® (NP), Intensity Factor® (IF) and ride duration. TSS® helps to determine the best combination of workouts and rest periods (text plagiarised). Since it uses normalized power and not avg power, I’m assuming it can differentiate between long duration, low intensity workouts and short duration, high intensity workouts.

I don’t have details for Zwift in particular, but Strava state, "We calculate Training Load by comparing your power during your ride to your FTP and determining how much load you put on your body during the workout. Training Load is a great way to determine how much rest you need after your workouts. The guide below will tell you how long after a workout it will take you to fully recover:

About 24 hours – 125 and lower
36-48 hours – 125-250
At least 3 days – 250-400
At least 5 days – 400+

Apparently, a well trained athlete can work with between a 500-700 weekly TSS score depending on recovery ability. 3 weeks on, one week off (off-week at roughly 70% TSS of an on-week).

For the TSS scores to make any sense, however, your FTP value will have to be reasonably accurate. You can do a Zwift workout (such as the 45 min FTP-Shorter) to automatically estimate your current FTP value.