Training Stress Balance (TSB)

Training Stress Balance (TSB) is the difference between CTL and ATL in the current Trainingload.ai PMC model. It shows how recent modeled load compares with the slower longer-term load level.

The UI may label TSB as Form or use freshness language. TSB is not a direct readiness, recovery, health, or performance measurement.

Example values are for UI preview only.

Formula used by Trainingload.ai

TSB_today = CTL_today − ATL_today

• Negative TSB means current ATL is above current CTL: recent modeled load is higher than the slower load level.
• Near-zero TSB means the two modeled averages are similar.
• Positive TSB means current ATL is below current CTL: recent modeled load is lower than the slower load level.

The sign describes a load relationship, not whether the athlete feels good or bad.

Why TSB moves quickly

Trainingload.ai uses a default seven-day smoothing period for ATL and 42 days for CTL. ATL therefore reacts faster when training rises or falls. During reduced training, ATL commonly drops faster and TSB rises; during a load build, ATL commonly rises faster and TSB falls.

Useful questions

TSB can help frame questions such as:

• Is recent modeled load above or below the longer load trend?
• Did a recovery week or taper reduce recent load as intended?
• Is a deep change explained by the scheduled plan and source activities?
• Does the load relationship agree with subjective state and workout execution?

It cannot independently answer:

• Is the athlete ready to race or test?
• Is a negative value productive or dangerous?
• Is a positive value optimal or evidence of undertraining?
• How many rest days are medically or physiologically required?

Do not use universal TSB zones

Ranges such as “peak,” “optimal training,” or “high risk” are heuristics from particular coaching contexts. They are not universal product guarantees and should not be treated as safety thresholds.

An athlete's useful range depends on load calculation, sport, training history, event demands, subjective response, and data quality. Establish personal context from comparable periods rather than forcing a generic target.

Use TSB in a taper or build

In a taper, confirm that volume and recent load are declining as intended while key execution remains appropriate. A rising TSB is evidence of the modeled load change, not proof that the taper has succeeded.

In a build, a falling TSB may be expected. Review whether the change matches the plan and whether session quality, subjective state, pain, illness, or recovery signals suggest that the next workout should be reconsidered.

Verify a TSB interpretation

• CTL and ATL use consistent and valid activity load.
• The comparison uses the intended sport and date range.
• The sign is described as a load relationship, not a diagnosis.
• Subjective state and completed-workout quality are included.
• A race, injury, illness, or recovery decision is not made from a generic TSB range.

Related pages

• Chronic Training Load (CTL)
• Acute Training Load (ATL)
• PMC Marathon Adjustment
• Training Analysis Workflow