Training Stress Score (TSS) is an important metric that quantifies your overall training load from a cycling session. This measurement allows you to assess the physical stress a workout imposes on your body, taking into account both intensity and duration.
Developed by Dr. Andrew Coggan, TSS is commonly utilized within training platforms like JOIN, TrainingPeaks, and Garmin to enhance training regimens and minimize the risk of overtraining.
TSS=FTP×3600(s×NP×IF)×100
Where:
s = Duration of the workout in seconds
NP = Normalized Power (a weighted average power output)
IF = Intensity Factor (ratio of NP to FTP)
FTP = Functional Threshold Power (maximum sustainable power over 60 minutes)
This formula quantifies training load by integrating both the workout’s duration and intensity. A higher TSS indicates a more demanding session, helping cyclists manage fatigue and optimize training adaptations.
TSS is calculated based on three critical components:
Normalized Power (NP): This indicates the physiological impact of a ride.
Functional Threshold Power (FTP): This represents the maximum power output an individual can sustain for approximately an hour.
Duration: The total time spent riding, measured in seconds.
By understanding TSS, you can effectively manage your training intensity, monitor fatigue levels, and adjust your workouts for improved performance.
To accurately calculate TSS, you will need:
Normalized Power (NP)
Functional Threshold Power (FTP)
Ride Duration
Normalized Power (NP) accounts for variations in effort throughout a ride, offering a more accurate reflection of its physiological impact compared to the average power. Real-world cycling includes fluctuations due to climbs, sprints, and coasting; NP smooths these variations.
Determining NP:
If you utilize a power meter, cycling applications like JOIN, Zwift, TrainingPeaks, or Garmin automatically calculate NP for each ride.
If you do not have access to a power meter, estimated power can be derived from heart rate-based calculations to approximate NP.
FTP is the highest average power you can sustain for about an hour. This measurement is critical for establishing training zones and calculating TSS.
Measuring FTP:
There are two principal methods for determining FTP:
Option 1: 60-Minute Time Trial: Ride at maximum effort for an hour and record your average power. This method delivers the most accurate FTP but can be quite demanding.
Option 2: FTP Test: A structured FTP test, such as the 12-minute FTP test available on JOIN, offers a quick and practical way to estimate your FTP. This workout is an excellent alternative for many cyclists:
Another option is to utilize an FTP calculator to estimate your threshold power based on recent test results.
Duration simply refers to the total time spent riding, which is measured in seconds for the TSS formula.
TSS = ((Seconds × NP × IF) / (FTP × 3600)) × 100
Where:
NP (Normalized Power) = 220W
FTP (Functional Threshold Power) = 250W
Duration = 90 minutes = 5400 seconds
IF (Intensity Factor) = NP ÷ FTP = 220 ÷ 250 = 0.88
Step-by-Step Calculation:
Multiply time (5400 sec) by power (220W) → 1,188,000
Multiply by intensity factor (0.88) → 1,047,840
Divide by (FTP × 3600) → (250 × 3600) = 900,000
Multiply by 100 → TSS ≈ 116
Thus, the ride results in a TSS of approximately 116, indicating a significant training load.
| TSS Range | Training Load | Effect on Fatigue |
|---|---|---|
| 0-50 | Low | Easy recovery ride, minimal fatigue |
| 50-100 | Moderate | Productive workout, manageable fatigue |
| 100-150 | High | Hard workout, requires recovery |
| 150-200 | Very High | Intense session, risk of overtraining |
| 200+ | Extreme | Heavy fatigue requires extended recovery |
Increasing your training load effectively is one of the biggest challenges in cycling. If you train again before fully recovering, you risk accumulating fatigue instead of making progress. Conversely, waiting too long between sessions can hinder your improvement. Training Stress Score (TSS) helps monitor your workload, allowing you to avoid overtraining while ensuring you're progressing.
However, it's important to remember that two training sessions with the same TSS can have very different effects.
For example, a high-intensity sprint session is not the same as a long endurance ride, even if their TSS values correspond. This is why it's essential to track both intensity and total TSS for optimal training.
Understanding your Training Stress Score (TSS) is useful for optimizing your cycling performance. By effectively managing your TSS, you can train smarter, recover better, and make consistent progress without overtraining. Below are four key strategies to help you adjust your training load based on TSS.
After each ride, it’s important to assess how your body feels. High TSS workouts place significant strain on your muscles and energy systems, so pay attention to the following:
Fatigue levels
Soreness, and
Overall energy.
If you find yourself feeling overly tired or sluggish, it may be a sign that your body needs more time to recover. Tracking these signals alongside your TSS data allows you to determine when to push forward and when to back off.
To maintain steady progress, incorporate recovery strategies into your routine. If your TSS has been accumulating rapidly over several sessions, consider scheduling a dedicated rest day or replacing an intense workout with an easy recovery ride. Active recovery, such as:
Low-intensity cycling
Stretching, or
Mobility work helps promote circulation and muscle repair while keeping you moving.
Proper rest prevents overtraining and ensures you can hit your next key session feeling fresh and ready.
Not all TSS is created equal. A long endurance ride and a short, high-intensity interval session can generate similar TSS values, but they affect your body differently. High-intensity workouts create more fatigue in a shorter time, while long endurance sessions build aerobic fitness with lower immediate strain. Balancing these types of rides is key to maintaining a productive training load without overloading your system.
A smart approach is to follow a hard session with an easier, longer ride. For example, after a sprint workout that generates a high TSS, your body needs time to recover from the neuromuscular stress. Instead of pushing through another intense workout the next day, opt for a steady, low-intensity endurance ride.
This allows you to maintain a solid weekly TSS while giving your body the recovery it needs. Consistently managing intensity and duration in this way helps you sustain progress and avoid burnout.
Monitoring your weekly TSS helps you identify patterns in your training and make informed adjustments. If your TSS is increasing too rapidly from week to week, you may be at risk of overtraining. A general rule is to increase TSS gradually (typically by no more than 5-10% per week) to allow your body to adapt safely. Drastic spikes in TSS can lead to excessive fatigue, reduced performance, and even injury.
On the flip side, if your TSS is consistently low, you might not be pushing yourself enough to see improvements. In this case, you can look at adding:
Structured intensity
Intervals and
Tempo efforts
Finding the right balance between training stress and recovery is crucial. Regularly reviewing your weekly TSS ensures that you’re training at an appropriate workload while minimizing the risk of plateauing or overloading.
Data-driven training is beneficial, but it’s equally important to listen to your body. TSS provides a numerical measure of training stress, but it doesn’t capture every aspect of recovery, such as:
Sleep Quality
Mental fatigue, or
Life stress.
If you’re feeling overly fatigued, sore, or unmotivated, these are clear indicators that your body needs more time to recover, regardless of what your TSS suggests.
Using tools like the JOIN app can help automate adjustments to your training plan based on your recovery status. The app analyzes your recent TSS, performance trends, and fatigue levels to recommend appropriate modifications. However, no technology can replace self-awareness.
By combining TSS tracking with personal intuition, you can fine-tune your training load, ensuring that you push yourself hard when needed and recover when necessary. This balance ultimately leads to better performance and long-term sustainability in your training.
JOIN offers an effective solution for automatically tracking your Training Stress Score (TSS), eliminating the need for manual tracking. Our app monitors workout intensity and your recovery needs, enabling it to automatically adjust your training plan. This ensures continuous progress while minimizing the risk of overtraining and injuries.
A standout feature of JOIN is readiness assessment, which aids in maintaining the appropriate training intensity for you. Following each workout, you are prompted to assess your condition based on muscle soreness and fatigue. If complete recovery has not occurred, the app will adapt to the next training session, helping you to prevent burnout and enhance performance.
With JOIN, the complexities of training are simplified, allowing for real-time adjustments to your workouts. Try JOIN for free today