Core TrainingPeaks Metrics Explained: Fitness, Form, Fatigue

TrainingPeaks offers essential metrics like Training Stress Score (TSS), Chronic Training Load (CTL) or Fitness, Acute Training Load (ATL) or Fatique, and Training Stress Balance (TSB) or Form. Using these metrics, cyclists can accurately measure progress, predict fitness and fatigue and strategically peak for competitions.

Keep in mind, the accuracy of these metrics relies on correctly setting Functional Threshold Power (FTP) in TrainingPeaks, or threshold and maximum heart rate for those using heart rate monitors.

Accurate FTP Settings

It is crucial to test and adjust FTP settings in TrainingPeaks approximately once a month to ensure metrics are correct.

Heart Rate Adjustments

For athletes without power meters, accurate heart rate thresholds are vital. These should be adjusted annually to reflect physiological changes, as heart rate typically decreases about one beat per minute per year.

Training Stress Score (TSS): Measuring Workout Impact

What is TSS?

Training Stress Score (TSS) is a crucial metric to quantify the intensity of a workout relative to the individual's fitness level. It measures the total workload of a training session and helps in comparing the stress imposed by different types of workouts. Understanding TSS is essential because it is the biggest aspect for calculating core TrainingPeaks metrics - fitness, form & fatique.

If you don't have a power data, you can use hrTSS, which is calculated based on your heart rate zones instead.

How is TSS Calculated?

TSS is calculated by considering the duration and intensity of a workout relative to the athlete’s Functional Threshold Power (FTP). The formula is as follows: 

• Normalized Power (NP): The average power adjusted for variation.
• Intensity Factor (IF): The ratio of NP to FTP. This calculation means that an hour-long workout done at FTP, which is a very intense level, yields a TSS of 100.

What is Considered a Good TSS? 

The notion of a 'good' TSS varies based on the workout's goal and the athlete's training plan. Generally, a TSS of 100 for a 1.5-hour workout indicates a high-intensity effort, suggesting that the training was quite challenging. This level of TSS is often targeted in workouts aimed at increasing fitness and endurance capabilities. Conversely, a TSS of 40 for the same duration (1.5 hours) would typically indicate a much lighter effort, likely a recovery ride or an easy session.

High-Intensity Workouts: A TSS of 100 for a 1.5-hour session indicates challenging training aimed at boosting fitness and endurance.

Moderate Effort: A TSS of 70 for 1.5 hours suggests a steady state or tempo effort.

Light Effort/Recovery Rides: A TSS of 40 for 1.5 hours is typical for lighter, recovery-focused sessions.

‍

Fitness (Chronic Training Load, CTL): A Measure of Endurance Fitness

What is CTL?

CTL basically tells us how much you have been training over time.

Chronic Training Load (CTL) or Fitness is a metric used in TrainingPeaks to quantify an athlete’s fitness level over time. It reflects the average daily training load an athlete has sustained over the past 42 days (or six weeks), providing a numerical value that indicates endurance fitness accumulated from consistent training.

How is CTL Calculated?

CTL is calculated through an exponential moving average of daily Training Stress Score (TSS) values 

This formula gradually integrates new training loads while considering the historical data, ensuring that the CTL value reflects recent training trends.

What is Considered Good CTL?

The ideal CTL varies based on an athlete's experience, training history, age, and competitive goals:

• Non-professional cyclists: For those balancing full-time jobs alongside cycling, a CTL between 100-110 is typically ideal, indicating that they are in top form.
• World Tour professionals: These athletes often achieve a CTL of 140-150, with values climbing towards 170 post-major tours like the Tour de France, reflecting their higher training volumes and intensity.

Seasonal Planning and CTL Management Properly structuring the training season is crucial to optimize CTL:

• Peak Form Phase: Aim to reach peak CTL during a designated 2-4 month period aligned with key races or events.
• Avoiding Plateaus: It is not advisable to maintain a high CTL year-round to prevent fitness plateaus and reduce the risk of burnout or overtraining.

Recommended Peak CTL Scores Overview:

• Amateur cyclists (full-time job): 100-110 CTL
• Elite amateur cyclists: 120-130 CTL
• Professional cyclists: 140-150 CTL
• Post-major tour professional cyclists: Up to 170 CTL

To achieve a CTL of 100, you would typically need to average about 700-750 TSS per week starting from a CTL of about 70. As your CTL increases, the amount of TSS needed to continue growing it also increases, requiring progressively more effort and strategic planning to sustain and improve your fitness levels. ‍

Form (Training Stress Balance, TSB): Monitoring Readiness and Fatigue

What is TSB?

TSB simply shows us your long term fatique

Training Stress Balance (TSB) or form (but i prefer to call it long-term fatique) is a metric used to gauge an athlete's balance between fitness and fatigue, essentially measuring their readiness to perform. It represents the difference between the fatigue from recent training loads and the fitness accumulated over a longer period.

How is TSB Calculated?

TSB is calculated by subtracting the Acute Training Load (ATL), which represents short-term fatigue, from the Chronic Training Load (CTL), which represents long-term fitness:

‍

This formula provides insight into whether an athlete is adequately recovered or still carrying significant fatigue.

What TSB Score Should I Aim For? TSB scores should fluctuate based on the training cycle:

• During Intensive Training Phases: As training intensity increases, TSB typically drops into the negative, ranging from -20 to -30. For athletes with higher fitness levels (e.g., CTL above 100), pushing to -40 or even -50 TSB can be sustainable and recommended.
• During Recovery or Adaptation Weeks: TSB should move into positive territory, typically between +5 to +15, indicating recovery and reduced fatigue.
• Pre-Race or Key Event Days: Aim for a TSB around +5 to ensure optimal performance without being overly rested or fatigued. For events spanning multiple days, a fresher state of around +10 TSB may be more advantageous.

Recommended TSB Scores Overview:

• Heavy Training Phases: -20 to -50 TSB (based on CTL level)
• Recovery/Adaptation Weeks: +5 to +15 TSB
• Race Day or Key Events: Approximately +5 TSB
• Multi-Day Events: Around +10 TSB

Fatique (Acute Training Load, ATL): Understanding Short-Term Fatigue

What is ATL? Acute Training Load (ATL) represents an athlete's short-term fatigue and is calculated from the daily training loads over a recent period. It's a measure of the exertion and stress an athlete has accumulated from training in the past 7 to 10 days. ATL is indicative of how tired an athlete might feel in the short run and can influence day-to-day training decisions.

How is ATL Calculated?

ATL is calculated using an exponential moving average of the daily Training Stress Score (TSS) values over a short-term period (commonly 7 days). This method provides a responsive measure of fatigue that reflects recent training activities. The calculation updates daily and helps athletes monitor how their bodies are handling the recent training loads.

Importance of Tracking ATL

While ATL is a useful indicator of short-term fatigue, it's often considered less critical to track rigorously compared to CTL and TSB. For athletes and coaches, ATL serves primarily as a contextual metric to adjust immediate training loads and recovery strategies. It’s particularly useful in preventing overtraining by signaling when too much training stress is accumulating too quickly.

Recommended Approach to ATL

There is no specific 'recommended' ATL value, as it will vary greatly depending on the individual's training phase, intensity, and personal capacity. Instead of aiming for a particular number, athletes should use ATL to gauge whether they need more recovery or can handle an increase in training load.

Conclusion

TrainingPeaks provides endurance athletes and coaches with powerful metrics to measure and manage training stress, fitness, fatigue, and form. By understanding and applying TSS, CTL, ATL, and TSB effectively, athletes can tailor their training programs to maximize their potential and peak at just the right moment.

If you would like to dive deeper into your data, you can explore this detailed article about advanced data analytics for cycling in WKO5 ->

At ProCyclingCoaching, we design long-term training plans using key TrainingPeaks metrics, ensuring cyclists understand their training phases and the purpose behind them. This approach empowers athletes to fully engage with and optimize their performance. You can contact us if you have any questions or if you'd like to explore how could we help you!