What Is TSS?
Training Stress Score (TSS) is a metric developed by Dr. Andrew Coggan that quantifies the overall training load of a workout. It accounts for both the intensity and duration of exercise, giving athletes a single number to compare workouts and manage fatigue. TSS is widely used in cycling with power meters and has been adapted for running and swimming.
A TSS of 100 represents training at your Functional Threshold Power (FTP) for one hour. Higher TSS values indicate greater physiological stress. By tracking daily and weekly TSS, athletes can optimize their training load to maximize fitness gains while minimizing overtraining risk.
TSS Formula
Normalized Power (NP) accounts for the variability of power output during a ride. It weights higher intensities more heavily since they cause disproportionate physiological stress. The Intensity Factor (IF) expresses workout intensity relative to your threshold.
TSS Guidelines
| TSS Range | Recovery | Description |
|---|---|---|
| < 150 | < 24 hours | Low to moderate stress, easy recovery |
| 150-300 | 24-48 hours | Hard workout, some residual fatigue |
| 300-450 | 48-72 hours | Very hard, significant fatigue likely |
| 450+ | 3-5 days | Epic effort, complete recovery needed |
How to Use TSS
- Track weekly TSS to maintain consistent training load and avoid overreaching.
- Chronic Training Load (CTL) is your rolling 42-day average TSS - your fitness marker.
- Acute Training Load (ATL) is your rolling 7-day average TSS - your fatigue marker.
- Training Stress Balance (TSB = CTL - ATL) indicates freshness; positive values mean ready to race.
- Aim for weekly TSS increases of no more than 5-10% to avoid overtraining.
Frequently Asked Questions
What is a good weekly TSS?
Recreational cyclists typically accumulate 300-500 TSS per week. Competitive amateur riders target 500-700 TSS. Professional cyclists can sustain 800-1200+ weekly TSS. Your optimal weekly TSS depends on your training history, recovery capacity, and life stress.
Can I calculate TSS without a power meter?
Yes. For running, rTSS can be estimated using pace and threshold pace. For heart rate-based training, hrTSS uses heart rate reserve percentage. However, power-based TSS is the most accurate because it directly measures work output.
What is the difference between TSS, rTSS, and hrTSS?
TSS is power-based (cycling). rTSS is pace-based (running), calculated using Normalized Graded Pace relative to threshold pace. hrTSS is heart rate-based and works for any sport but is less accurate due to cardiac lag and drift. All three aim to quantify the same thing: total training stress.