TSS
Training Stress Score
TSS (Training Stress Score) quantifies workout intensity and duration into a single number. Learn how TSS is calculated, what values mean, and how to use it for training load management.
Quick Answer
TSS — (Training Stress Score) is a metric that quantifies the training load of a workout by combining duration and intensity relative to your FTP. A TSS of 100 equals one hour at your threshold power (FTP).
What Does TSS Mean?
TSS stands for Training Stress Score. Developed by Dr. Andrew Coggan, it provides a single number that captures both how hard and how long a workout was, relative to your current fitness (FTP).
TSS answers the question: "How stressful was this workout for my body?"
A workout with a TSS of 100 is equivalent to riding for one hour exactly at your FTP. Easier rides generate less TSS; harder or longer rides generate more.
Use our TSS Calculator to calculate TSS for your rides.
How TSS is Calculated
TSS requires three inputs:
- Duration – How long the workout lasted
- Normalized Power (NP) – The "effective" average power
- FTP – Your current Functional Threshold Power
TSS Formula:
TSS = (Duration in seconds × NP × IF) / (FTP × 3600) × 100
Where IF (Intensity Factor) = NP / FTP
Simplified:
TSS = (Duration in hours) × (IF)² × 100
Example Calculation
A 90-minute ride with Normalized Power of 200W and FTP of 250W:
- IF = 200 / 250 = 0.80
- TSS = 1.5 hours × (0.80)² × 100 = 1.5 × 0.64 × 100 = 96 TSS
TSS Guidelines by Duration
| Ride Type | Typical TSS | Example |
|---|---|---|
| Recovery spin | 20-40 | 1 hour at 55% FTP |
| Endurance ride | 50-80 | 2 hours at 65% FTP |
| Long ride | 100-200 | 3-5 hours endurance |
| Hard interval session | 80-120 | 90 min with intervals |
| Race (1 hour) | 100-110 | Full effort |
| Century ride | 200-350 | 100 miles |
Recovery Time by TSS
TSS helps predict recovery needs:
| TSS | Recovery Time |
|---|---|
| < 150 | Low – recovered by next day |
| 150-300 | Medium – some residual fatigue |
| 300-450 | High – need 2-3 easy days |
| > 450 | Very high – need multiple recovery days |
Weekly TSS Guidelines
Managing weekly TSS helps prevent overtraining:
| Athlete Level | Weekly TSS Range |
|---|---|
| Recreational | 200-350 |
| Enthusiast | 350-500 |
| Competitive amateur | 500-700 |
| Elite amateur | 700-900 |
| Professional | 900-1200+ |
Increase weekly TSS by no more than 10-15% per week to avoid injury and overtraining.
TSS vs Other Metrics
| Metric | What It Measures | Sport |
|---|---|---|
| TSS | Power-based training load | Cycling |
| rTSS | Running training stress | Running |
| hrTSS | Heart rate-based stress | Any |
| TRIMP | HR-based training impulse | Any |
TSS is the most accurate for cyclists with power meters because power data is more precise than heart rate.
CTL, ATL, and TSB
TSS feeds into longer-term training metrics:
| Metric | Full Name | What It Represents |
|---|---|---|
| CTL | Chronic Training Load | 42-day rolling TSS average (fitness) |
| ATL | Acute Training Load | 7-day rolling TSS average (fatigue) |
| TSB | Training Stress Balance | CTL - ATL (form/freshness) |
TSB Guidelines:
- Negative TSB = fatigue exceeds fitness (training hard)
- Positive TSB = fitness exceeds fatigue (fresh for racing)
- Optimal race TSB = +15 to +25
Common Questions
What's a good TSS for a training ride?
It depends on your goals and recovery status. Most structured workouts fall between 60-120 TSS. Sweet spot training sessions typically generate 80-100 TSS in 90 minutes.
Can I have too much weekly TSS?
Yes. Chronically high TSS without adequate recovery leads to overtraining, decreased performance, and increased injury risk. Monitor your Intensity Factor distribution—most training should be in Zones 1-2.
How does TSS relate to FTP improvements?
Consistent TSS accumulation at appropriate intensities drives FTP adaptation. Most athletes need 400-700 weekly TSS with 80% in endurance zones and 20% at higher intensities to steadily improve FTP.
Why is my TSS lower indoors?
Indoor TSS often matches outdoor rides despite feeling harder due to heat, boredom, and constant pedaling. If your indoor FTP differs from outdoor, use separate values for accurate TSS.