Training Stress Balance (TSB)

You can think of Training Stress Balance (TSB) as a snapshot of whether you’re carrying fatigue or feeling fresh. It’s commonly derived from CTL (long-term load) and ATL (short-term load), so it responds to your recent training and recovery pattern.

Example card: values are for UI preview only. Interpret using your own data and trends.

Core Concepts

• Derived from CTL and ATL: TSB is not directly measured; it is the difference between fitness and fatigue (often using yesterday’s values to represent today’s morning readiness).
• Sensitive to recent changes: because ATL (often 7 days) changes faster than CTL (often 42 days), TSB reacts quickly to recovery/tapering.
• Higher isn’t always better: high TSB can mean great recovery, but it can also mean undertraining (falling CTL). Always interpret with CTL level and trend.

How to interpret and use it

• TSB rising: usually means training volume dropped or you entered a taper. You may feel fresher, but watch whether CTL is falling too much.
• TSB falling: usually means load increased and fatigue accumulated. Normal in a build, but rapid/deep drops increase recovery and injury-risk concerns.
• Use with ATL/CTL: view Fatigue | Acute Training Load (ATL) and Fitness | Chronic Training Load (CTL) together with TSB.

How Trainingload.ai uses TSB

Trainingload.ai uses TSB as a readiness context signal. A very negative TSB can prompt the AI coach to examine whether upcoming hard sessions still make sense. A positive TSB before a test or race can support keeping intensity while reducing volume.

TSB should not be used as a command. The better use is to ask: does the current plan match the athlete’s intended training phase and recovery state?

Formula

TSB is the difference between fitness and fatigue:

TSB_today = CTL_yesterday - ATL_yesterday

• Positive (+): you are relatively fresh; good for racing or hard testing.
• Negative (-): fatigue is accumulated; good for training blocks, not ideal for peak performance.

Note: using “yesterday’s” CTL and ATL is a common convention to represent how you feel when you wake up today.

Interpreting TSB ranges

In classic PMC, these heuristic ranges are often used for planning (individual differences and sport specifics still matter):

Practical strategies

1. Tapering

This is one of the most practical applications of TSB. In the final 7–14 days before an important race:

• Keep intensity: do short race-intensity efforts to maintain neuromuscular sharpness.
• Cut volume: reduce training duration (often TSS down 40–60%).
• Result: because ATL (7 days) drops much faster than CTL (42 days), TSB can rise quickly from negative values into a fresher range.

2. Training camp overload

In an early-season base phase, you might plan a 1–2 week overload block that intentionally drives TSB below -30.

• Key: after the block, schedule real recovery so the body can absorb the stress.

3. Avoid long-term stagnation

If your TSB sits around +5 to +10 for a long time, your load may be too low and CTL may stagnate. Increase training load to bring TSB back toward the -10 to -30 range.

Limitations

TSB is model-based. It can’t “see”:

• life stress (work, family)
• sleep quality
• nutrition
• early signs of illness

So, never ignore how you actually feel just to chase a TSB number. If TSB says +10 (fresh) but you feel awful, trust your body and rest.

References

• The Science of the TrainingPeaks Performance Manager (Andrew Coggan)
• Modeling Human Performance (Fellrnr)