Training Load Metrics: A Complete Guide to TSS, IF, and CTL

Introduction

Opening TrainingPeaks or intervals.icu, a pile of English abbreviations like TSS, IF, CTL, ATL, TSB can make your head spin. But these metrics are part of the “Training Load Management System” established by Andy Coggan and Hunter Allen, which can scientifically quantify your training load, predict performance, and prevent overtraining.

Five Core Metrics

TSS Calculation Formula

TSS = (duration in seconds × NP × IF) / (FTP × 3600) × 100

Simplified version:

• 1 hour at FTP intensity = 100 TSS
• 1 hour at Z2 (IF 0.7) = 49 TSS
• 2 hours at Z3 (IF 0.85) = 145 TSS
• 4 hours mixed Z2 + Z3 (IF 0.75) = 225 TSS

IF Intensity Reference

Interpreting CTL/ATL/TSB

CTL is the exponentially weighted average of the past 42 days, representing “accumulated fitness.” Beginners have a CTL of around 30, advanced amateurs around 60–80, elite amateurs 100+, and pro riders 130+.

ATL is the average of the past 7 days, representing “short-term fatigue.”

TSB = CTL - ATL, representing “freshness”:

• TSB > +10: Too much rest, possible fitness loss
• TSB +5 ~ +25: Optimal race-day form
• TSB -10 ~ 0: Training accumulation in progress
• TSB < -20: Overtraining warning sign

Weekly TSS Planning Recommendations

Pre-Race TSB Planning

Race-day TSB is critical:

• A-priority races: TSB +15 ~ +25 (adequate taper)
• B-priority races: TSB +5 ~ +10 (racing during training)
• C-priority races: TSB -5 ~ 0 (testing during high training volume)

Practical Advice

First, FTP must be accurate—TSS relies entirely on FTP; if FTP is overestimated by 20W, TSS will be underestimated by 8%, and CTL will be off. Second, retest FTP every 8 weeks to adjust your data. Third, don’t increase CTL by more than 8 points per month; beginners should stay under 5 points, otherwise injury rates spike. Fourth, if TSB stays below -20 for more than two weeks, cut volume immediately—you may be entering overtraining. Fifth, TSS does not reflect mental fatigue—when work stress is high or sleep is poor, even a low TSS number can mean excessive fatigue; listen to your body.

Conclusion

TSS/CTL/TSB are the “dashboard of training.” For those who train scientifically, these numbers matter more than any KOM. But don’t fall into the “number-chasing trap”—the goal isn’t a CTL of 100, but optimal form on race day. Treat these metrics as aids and make listening to your body the main focus. When you can precisely dial in a TSB of +20 before a race and hit an NP/FTP ratio of 0.92 on race day, that is the triumph of training science.

Related Reading

• TSS, CTL, ATL: A Complete Breakdown of the Three Core Training Load Metrics
• Training Load Management: Daily Application of TSS, ATL, CTL, and TSB
• TSS, CTL, ATL, TSB Complete Guide: Calculation Principles and Applications of Training Stress Index
• Training Load and Fatigue Management: Applying CTL, ATL, and TSB