Acute Training Load (ATL)

Acute Training Load (ATL) is a fast-moving exponential average of daily training load. It emphasizes recent sessions and reacts faster than CTL.

The UI may label ATL as Fatigue, but ATL does not directly measure physiological or subjective fatigue. It is a recent-load model that can provide fatigue context when combined with how the athlete feels and performs.

Example values are for UI preview only.

Formula used by Trainingload.ai

Trainingload.ai uses a standard exponential moving-average smoothing factor with a default ATL period of seven days:

λ_ATL = 2 / (7 + 1)
ATL_today = daily_load × λ_ATL + ATL_yesterday × (1 − λ_ATL)

This is not a simple total or average of the last seven calendar days. Recent inputs have more weight and older inputs decay gradually.

How ATL changes

• A high-load day can move ATL noticeably because the smoothing period is short.
• Several reduced-load days usually lower ATL faster than CTL.
• Recalculated activity load, duplicates, or source changes can alter the recent series.
• An ATL increase shows more recent modeled load; it does not reveal whether that load was absorbed successfully.

How to use ATL

Use ATL to identify periods that deserve closer review:

• Several hard or long sessions were stacked together.
• The recent load differs from the active plan.
• A recovery week or taper is reducing load.
• Subjective state or execution quality changed during a recent load increase.

Then open the activities and check sport, duration, intensity, sensor quality, load source, pain or illness signals, sleep, and Session RPE where available.

What ATL cannot decide

ATL alone cannot determine:

• Whether the athlete is physiologically fatigued.
• Whether an ATL level is safe or unsafe.
• Whether training should stop.
• Whether a taper has produced race readiness.
• Whether a running week is more dangerous than a cycling week.

Those decisions require sport and impact context, training history, symptoms, subjective state, and professional guidance when health or injury is involved.

Read ATL with CTL and TSB

Because ATL reacts faster than CTL, it often moves above CTL during a load build and drops below it during reduced training. TSB expresses their current difference.

This relationship describes the model. Terms such as fitness, fatigue, and form are convenient labels, not direct measurements.

Verify an ATL interpretation

• Recent activities and their load sources are valid.
• The sport and date window match the decision.
• A load change is separated from claims about felt fatigue or recovery.
• Subjective and performance evidence is included when adjusting a workout.
• Health, pain, or injury decisions are not based on ATL alone.

Related pages

• Chronic Training Load (CTL)
• Training Stress Balance (TSB)
• Training Analysis Workflow