Training Stress Score (TSS) is a crucial metric in cycling, designed to quantify the overall load and intensity of a workout. Developed by Dr. Andy Coggan and Hunter Allen, TSS helps cyclists track training progress, balance effort and recovery, and optimize performance. Whether you’re training for endurance, racing, or improving overall fitness, understanding TSS is key to structuring an effective cycling regimen.
What is TSS?
TSS (Training Stress Score) is a numerical value that represents the physiological impact of a workout. It factors in both duration and intensity to provide a comprehensive measure of training load.
Originally developed as part of TrainingPeaks, TSS was inspired by heart rate-based training impulse (TRIMP) models and has since become a gold standard in structured training programs. It enables cyclists to compare different types of workouts—whether it’s a short, high-intensity session or a long endurance ride—on a single scale.
How is TSS Calculated?
The formula for TSS is:
TSS = (seconds × Normalized Power × Intensity Factor) / (FTP × 3600) × 100
Key Components:
- Functional Threshold Power (FTP) – The maximum power a rider can sustain for one hour.
- Normalized Power (NP) – An adjusted power output measurement that accounts for fluctuations in effort.
- Intensity Factor (IF) – The ratio of NP to FTP, representing the workout’s relative intensity.
In simpler terms, riding for one hour at FTP results in a TSS of 100. A lower-intensity ride for the same duration will generate a lower TSS, while a shorter, high-intensity workout can also reach 100 TSS due to increased effort.
Why is TSS Important?
TSS plays a significant role in training by:
- Tracking training load over time – Helps cyclists monitor progress and avoid overtraining.
- Balancing training and recovery – Ensures that workouts are neither too easy nor excessively taxing.
- Providing insight into fitness adaptations – A steadily increasing weekly TSS suggests improved endurance and strength.
- Aiding in goal setting – Helps cyclists structure training plans based on desired workload.
TSS Categories and Their Implications
Understanding TSS scores can help cyclists interpret their workouts and adjust their plans accordingly:
- Low TSS (1-100) – Typically an easy recovery ride or light endurance session.
- Moderate TSS (100-200) – Represents a solid workout, such as tempo efforts or long rides at moderate intensity.
- High TSS (200-300) – Indicates a demanding session, often seen in intense interval training or long-distance rides.
- Very High TSS (300+) – Associated with extremely long or high-intensity efforts, often requiring extended recovery time.
Weekly TSS and Fatigue Management
For structured training, tracking weekly TSS helps balance effort and recovery:
- Beginner cyclists – 200-400 TSS per week.
- Intermediate cyclists – 400-700 TSS per week.
- Advanced cyclists – 700+ TSS per week, often including structured periodization.
Limitations of TSS
While TSS is a valuable tool, it has limitations:
1. TSS Doesn’t Consider Workout Structure
Two workouts can have the same TSS but affect the body differently. A steady endurance ride and an intense interval session may both generate 150 TSS, but their impact on fatigue and adaptation varies.
2. TSS Doesn’t Account for Fatigue Accumulation
Repeated high-TSS days lead to increasing fatigue, even if individual sessions seem manageable. Tracking Chronic Training Load (CTL) and Acute Training Load (ATL) alongside TSS provides better insight into long-term performance trends.
3. TSS Ignores External Factors
Nutrition, sleep, life stress, and environmental conditions affect performance but aren’t reflected in TSS calculations. It’s important to use subjective feedback alongside TSS for a complete picture of training readiness.
Using TSS to Plan Training
TSS is most effective when integrated into structured training plans.
1. Setting Weekly TSS Targets
- Base training (low-intensity endurance work): 300-600 TSS/week
- Build phase (progressive overload and interval training): 600-900 TSS/week
- Peak phase (race preparation and tapering): 500-800 TSS/week
2. Using TSS for Periodization
TSS helps guide training phases:
- Accumulation Phase: Gradually increasing TSS to build endurance.
- Intensity Phase: Higher IF workouts to boost fitness.
- Tapering Phase: Reducing TSS before key events for peak performance.
3. Balancing Training and Recovery
High-TSS weeks should be followed by deload weeks (~50-60% of regular TSS) to ensure proper recovery and prevent burnout.
So, what is TSS in cycling? It is an essential metric for cyclists, helping quantify training load, balance effort, and optimize performance. However, it should be used alongside other indicators like heart rate, power zones, and subjective feedback to provide a well-rounded view of fitness.
By understanding and applying TSS correctly, cyclists can train smarter, avoid overtraining, and maximize their potential on the bike.
Training Plans
Are you interested in taking the next step with your training? Take a look at the affordable and flexible cycling training plans below.
