TSS stands for Training Stress Score, a metric that measures the total workload of a cycling session.
It combines intensity and duration into a single number to show how much stress the workout placed on your body.
The higher the TSS, the more demanding the session was.
TSS is based on your Functional Threshold Power (FTP), which represents the effort you can sustain for about an hour.
A ride at FTP for exactly one hour equals 100 TSS.
More precisely, TSS is calculated using Normalized Power (NP) — not average power — along with your FTP and ride duration. NP adjusts for the variability of real-world riding, which is why two rides with the same average watts can produce very different TSS values.
Lower-intensity, longer rides and short, intense efforts can result in similar TSS scores, but with different physiological effects.
This metric helps track fatigue, manage weekly load, and plan recovery.
It’s commonly used in training software to monitor performance and avoid overtraining.
TSS also helps compare different types of workouts and understand their impact on your fitness.
By analyzing TSS over time, you can build a more balanced and effective training plan.
Understanding TSS is key to training smarter, not just harder.