Training Load Numbers That Predict Burnout

Power meters and training software have made cycling more data-driven than ever. Among the metrics cluttering your dashboard, three letters matter more than most when it comes to predicting burnout and optimizing performance: TSS, ATL, and CTL. Understanding how these numbers interact tells you whether your training is building fitness or quietly leading toward a breakdown.

What Is TSS (Training Stress Score)?

Training Stress Score quantifies the physical demand of a single workout by combining intensity and duration into one number. A one-hour ride at exactly your FTP produces a TSS of 100. Easier rides generate lower scores; harder or longer rides produce higher ones.

The formula accounts for how long you rode and how hard relative to your threshold. Thirty minutes at FTP gives you 50 TSS. Two hours at 70% of FTP might yield 120 TSS. Sprint intervals that last 45 minutes could hit 80 TSS due to high intensity despite short duration.

TSS tells you the training load of individual workouts, but it doesn’t predict how that load accumulates over time or whether you can handle it. That’s where ATL and CTL come in.

CTL: Chronic Training Load (Your Fitness)

Chronic Training Load represents your fitness—specifically, the training stress you’ve absorbed and adapted to over roughly the past six weeks. Think of it as a rolling 42-day weighted average of your daily TSS, with recent days counting slightly less than older ones to create a smooth trend line.

A CTL of 80 means you’re averaging about 80 TSS per day when smoothed over six weeks. An experienced cyclist might carry a CTL of 100+ during peak season, while someone newer to structured training might operate around 40-60.

Higher CTL generally correlates with better fitness and endurance, but only if you built it gradually. Jumping from a CTL of 50 to 90 in a month doesn’t mean you’re twice as fit—it means you’re probably heading toward exhaustion.

ATL: Acute Training Load (Your Fatigue)

Acute Training Load tracks your recent training stress over approximately the past week (a 7-day weighted average). It represents fatigue—the immediate load your body is currently managing.

ATL responds quickly to changes in training. A hard block of intervals sends it spiking. A rest day or easy week causes it to drop. Unlike CTL, which moves slowly and reflects accumulated fitness, ATL shows what you’re dealing with right now.

By itself, ATL doesn’t tell you much. A high ATL could mean you’re in a productive training block or that you’re digging a hole you can’t recover from. The critical insight comes from comparing ATL to CTL.

TSB: The Number That Predicts Burnout

Training Stress Balance (TSB) is simply CTL minus ATL. It reveals whether your recent training load (fatigue) is higher or lower than your established fitness level.

A negative TSB means you’re carrying more acute fatigue than your fitness can comfortably handle—you’re in a productive training block or potentially overreaching. A positive TSB indicates you’re fresher, with less recent stress than your fitness baseline would suggest.

Here’s how to interpret TSB values:

• TSB: -10 to -30 – Functional overreaching. You’re training hard, accumulating fatigue, but building fitness. This is productive if you allow recovery before TSB drops further.
• TSB: -30 to -50 – Danger zone. You’re deep into fatigue accumulation. Performance will suffer, and risk of illness or injury increases. Short periods here can work if you have a recovery block planned immediately after.
• TSB: Below -50 – Likely overtraining. Most athletes can’t sustain this level of accumulated fatigue without breaking down. If you’re here for more than a few days, stop and recover.
• TSB: -5 to +5 – Balanced state. Your recent training matches your fitness level. Good for maintenance phases or steady training.
• TSB: +10 to +25 – Freshness for performance. You’ve reduced training load, dissipated fatigue, but retained fitness. Peak racing form typically occurs here.
• TSB: Above +25 – Possibly too fresh or detraining. Extended time here means you’re not training enough to maintain fitness.

The CTL Ramp Rate: How Fast Is Too Fast?

A general rule suggests increasing CTL by no more than 5-8 points per week. Push beyond that, and your body can’t adapt fast enough. Injuries, illness, and burnout become likely.

If your CTL is 60 and you want to reach 80, that’s a 20-point increase requiring at least 3-4 weeks of progressive training. Trying to do it in two weeks means cramming 40% more training load into a timeframe where your adaptation capacity can handle maybe 15%. The math doesn’t work, and your body will make that clear.

Experienced athletes with years of training can sometimes handle slightly faster ramps. Newer cyclists or those returning from time off should be more conservative. Age, life stress, sleep quality, and nutrition all affect how quickly you can safely build CTL.

Why TSB Predicts Burnout Better Than How You Feel

Subjective feelings lag behind physiological reality. You might feel fine while TSB sits at -40, especially if you’re motivated and the weather is good. But the damage accumulates beneath your awareness. By the time you consciously feel overtrained, you’ve likely been in a deficit state for weeks.

TSB gives you an objective early warning system. When it drops below -30 and stays there, you know trouble is coming even if you don’t feel it yet. This allows you to insert recovery before motivation disappears, performance craters, or you get sick.

The reverse is also true: you might feel tired and sluggish after a rest week, but TSB shows you’re at +15—fresh and ready for hard training. Trust the numbers over your momentary feelings, especially when they contradict.

Practical Application: Using These Metrics to Train Smarter

Start by establishing your baseline CTL during a typical training period. If you’re consistently training and feel good, that CTL represents sustainable fitness for you right now. Note this number.

When planning a training block, decide how much you want to increase CTL and over what timeframe. Add 5-7 points per week maximum. Schedule recovery weeks every 3-4 weeks where you reduce TSS by 40-60%, allowing ATL to drop and TSB to recover to slightly positive territory.

Monitor TSB daily. If it approaches -30, your next training decision should prioritize recovery, not more stress. Replace a hard workout with an easy spin. Take a full rest day. Sleep more. The specific intervention matters less than recognizing the trend and responding before it becomes a problem.

Before important events, plan a taper by reducing TSS over 1-2 weeks. This lets ATL drop while CTL stays relatively stable, driving TSB positive. Peak form emerges when that balance hits your personal sweet spot—often around +15 to +20 for most athletes.

The Limits of These Metrics

TSS, CTL, ATL, and TSB are models, not perfect representations of reality. They assume FTP is accurate, every ride is recorded with power data, and all training stress comes from cycling. Life stress, poor sleep, and non-cycling activities don’t appear in these numbers but absolutely affect your capacity to handle training load.

Use these metrics as guides, not absolute rules. If TSB is at -20 but you feel terrible, rest anyway. If CTL is climbing at the recommended rate but injuries keep appearing, slow down. The numbers reveal patterns, but your body has the final word.

That said, consistently ignoring what TSS, ATL, CTL, and TSB are telling you is how most cyclists end up overtrained without understanding why. The data won’t force you to make smart decisions, but it makes the smart decision obvious—if you’re willing to look.