The Performance Management Chart
If you have spent any time in endurance training communities, you have likely encountered the terms CTL, ATL, and TSB. Together, these three metrics form the Performance Management Chart (PMC), a model originally developed by Dr. Andrew Coggan for cycling that has since been adopted across endurance sports. Understanding these numbers gives you a powerful lens into your training status.
Chronic Training Load (CTL): Your Fitness
CTL represents your long-term training load, calculated as an exponentially weighted moving average of your daily training stress over approximately 42 days. Think of it as your accumulated fitness. A rising CTL means you are getting fitter through consistent training. A declining CTL indicates you have been training less.
CTL does not change dramatically from day to day. It responds to sustained, consistent effort. This is why building an aerobic base takes weeks, not days. An athlete with a CTL of 80 has a substantially deeper fitness reservoir than one at 40, assuming similar training backgrounds.
Acute Training Load (ATL): Your Fatigue
ATL captures your short-term training load, typically using a 7-day exponentially weighted average. It reflects recent training stress and serves as a proxy for fatigue. After a hard training week, your ATL spikes. During a recovery week, it drops.
ATL responds much faster than CTL. A single hard workout can noticeably raise your ATL, while your CTL barely moves. This difference in response time is what makes the model useful.
Training Stress Balance (TSB): Your Form
TSB is simply CTL minus ATL. When your fitness exceeds your fatigue, TSB is positive, and you are theoretically fresh and ready to perform. When fatigue outweighs fitness, TSB is negative, meaning you are carrying accumulated training stress.
Most athletes train with a negative TSB during build phases and aim for a positive TSB on race day. A TSB between plus 10 and plus 30 is often cited as the sweet spot for peak performance, though individual variation is significant.
Practical Applications
Monitoring these metrics helps you answer critical training questions. Are you building fitness consistently? Is fatigue accumulating dangerously? Are you tapering enough before your goal event? The PMC transforms subjective feelings into objective trends.
Limitations to Keep in Mind
The PMC model is powerful but imperfect. It does not account for training quality, life stress, sleep, nutrition, or illness. A TSB of plus 15 means nothing if you are fighting a cold. Use these metrics as one input among many, not as an absolute truth.
Track Your PMC With Strilab
Strilab calculates your CTL, ATL, and TSB automatically from your synced training data and displays them on your dashboard. Watch your fitness build, manage your fatigue, and time your peak with confidence. Let the data guide your training decisions.