If you’ve ever looked at your TrainingPeaks dashboard and wondered what TSS, CTL, and ATL mean, you’re not alone. These training peaks metrics are powerful tools that help you track training load, recovery, and fitness, but they can seem confusing at first. The good news? You don’t need a sports science degree to understand them.

This post breaks down what these numbers mean and, more importantly, how you can use them to train smarter and avoid overtraining.
What is TSS (Training Stress Score)?
TSS measures how much training stress a workout puts on your body. It takes into account both the intensity and duration of your workout to give you a single number that represents how hard the session was.
Why it matters:
Helps track how much work you’re doing.
Makes it easier to compare different types of workouts (e.g., a short, intense session vs. a long endurance ride).
Gives insight into how much fatigue you're accumulating.
How it’s calculated:
A 1-hour workout at your threshold power or pace = 100 TSS
A harder workout = Higher TSS
A shorter/easier workout = Lower TSS
Key takeaway: Higher TSS means more training stress, but that doesn’t mean every workout should be high-TSS. Balance is key!
What is CTL (Chronic Training Load)?
CTL is your long-term training load—think of it as your “fitness” level. It’s an average of your daily TSS over the past 42 days.
Why it matters:
A rising CTL means you’re getting fitter.
A dropping CTL means you’re losing fitness (or tapering before a race).
Sudden spikes in CTL might indicate too much training stress, increasing injury risk.
Key takeaway: Steady, gradual increases in CTL lead to sustainable fitness gains. If your CTL is climbing too fast, you might be overdoing it.
What is ATL (Acute Training Load)?
ATL measures how much fatigue you’re carrying from recent workouts. It’s similar to CTL but focuses on the last 7 days instead of 42.
Why it matters:
If ATL is too high, you might be overtraining.
If ATL is too low, you might not be training hard enough to improve.
A high ATL combined with a low CTL means your body isn’t fully adapted to the training load yet.
Key takeaway: ATL helps you understand if you’re pushing too hard or need more recovery.

How to Use These Metrics in Your Training
Monitor your Training Stress Balance (TSB) – This is simply CTL minus ATL and tells you if you're fresh or fatigued.
TSB near zero: You're maintaining your fitness.
Negative TSB: You're in a high-fatigue state (normal after a tough training block).
Positive TSB: You’re fresh and ready to perform—perfect for race day!
Plan Your Training Load – Increase CTL gradually (5-7 points per week max) to avoid injury and burnout.
Balance Training and Recovery – If ATL is too high for too long, schedule more recovery days or easier sessions.
Taper for Races – Reduce ATL before key events to allow CTL to stay high while fatigue drops, giving you peak performance.
Final Thoughts
Understanding TSS, CTL, and ATL can help you train smarter, track progress, and avoid overtraining. By keeping an eye on these metrics, you’ll know when to push hard and when to back off—leading to better fitness and stronger performances. Or you can just hire a coach and not worry about any of this!
Next time you log into TrainingPeaks, check out your numbers and start using them to fine-tune your training!
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