Neverpedia
Training load
TSS (Training Stress Score)
A single number summarizing how much physiological stress a workout produced, scaled to FTP.
Training Stress Score (TSS) is a single number that summarizes the physiological cost of a workout. It is scaled to FTP — a one-hour effort at FTP equals 100 TSS by definition.
How it is calculated
TSS = (duration_seconds × NP × IF) / (FTP × 3600) × 100
In plain terms: a harder ride (higher Intensity Factor) earns more TSS per minute than an easier ride.
Why it matters
TSS is the building block for CTL, ATL, and TSB. Without a consistent TSS calculation across your rides, training load metrics fall apart.
- 50 TSS — easy hour
- 100 TSS — solid endurance hour
- 200 TSS — a long, hard ride
- 300+ TSS — a big day
Common misconceptions
- TSS treats all intensities by formula — 100 TSS of intervals is not biologically equal to 100 TSS of endurance even though the number is the same.
- TSS depends on FTP being correct. A wrong FTP makes every TSS number wrong.
- TSS is for cycling power. Running TSS (rTSS) and heart-rate TSS (hrTSS) are approximations.
Related concepts
NP, IF, CTL, ATL, TSB.