Fatigue: what acute training load shows
A shorter view of training
Fatigue, often called acute training load (ATL), is a weighted average of recent daily training load. The common default time constant is seven days, making it more responsive to a training block or rest than the longer-term fitness line.
Change the load and length of the block. The dashed line rises and falls faster than the solid line.
Watch recent load respond
Start with three weeks at 50 load a day. Change the following block, then move through the timeline.
Illustration starts both trends at 50. Daily updates use 1/42 and 1/7; form is same-day fitness minus fatigue. Platforms may use different timing and settings. These curves describe the model, not your body.
A shorter view of training
Fatigue, often called acute training load (ATL), is a weighted average of recent daily training load. The common default time constant is seven days, making it more responsive to a training block or rest than the longer-term fitness line.
Change the load and length of the block. The dashed line rises and falls faster than the solid line.
Why it falls after rest
In the example, each day adds one seventh of the difference between that day’s load and yesterday’s acute load. A rest day has zero training load, so the calculated number moves down.
That does not guarantee your body has recovered. Sleep, life stress, illness, soreness and the specific sessions are not fully represented by the score.
The label is a model
A high acute load indicates a recent accumulation of recorded load. It does not measure muscle damage, nervous system fatigue or your ability to complete tomorrow’s session.
Pay attention to how you feel and perform, the purpose of the training block and changes in circumstances. A single universal fatigue number cannot capture every person.
Compare like with like
Missing activities or switching from power-based to estimated scores can shift the line. Threshold settings and the selected time constant also matter.
An easy day can reduce the modelled value if its load is below the current acute load; it need not be a complete rest day.
A day-by-day example
With acute load at 50, a day scored at 100 raises the example to about 57.1: 50 + (100 − 50) ÷ 7. A day with a lower score moves it back toward that day’s load.
The timeline keeps the longer-term line visible so you can see why two averages of the same training history can move at different speeds.
What a rest day can and cannot show
A zero-load day reduces the calculated acute load, but it does not account for a poor night of sleep or other stress. An easier training day can also lower the number when its score is below the current average.
Use the curve to ask what changed in training, then consider whether your response matches the picture.
Watch the pattern, not a universal limit
A hard workout may be intentional and useful in a training plan. Its effect depends on the athlete, the surrounding sessions and the ability to recover.
Compare changes with your own history and circumstances instead of applying a single cut-off to everyone.