Metric guide
Training load is a model, not an injury alarm
The useful version
Use load to ask why your training changed. Do not let one ratio make the decision for you.
What the model calculates
Most systems assign each workout a stress value, then apply faster and slower moving averages. Acute training load reacts quickly. Chronic training load moves more slowly.
The result depends on the input. Heart-rate load, power-based stress and simple duration do not describe the same thing.
How to read ATL, CTL and TSB
ATL is commonly read as recent fatigue, CTL as accumulated fitness and TSB as the difference between them. A negative balance is normal during productive training, while a positive balance often appears during a taper.
The useful signal is the shape of the trend around your own training. Exact thresholds should not be mistaken for biological boundaries.
Where the model stops
Load does not include technique, tissue tolerance, sleep, illness or the context of a new sport. The popular claim that one acute-to-chronic ratio can predict injury has also been heavily contested.
Combine the chart with symptoms, session quality and the training change that created the number.
Go one step further
Questions
What people usually ask
What are ATL and CTL?
Acute training load is a short-term estimate of fatigue, while chronic training load is a longer-term estimate of accumulated fitness. The exact time constants and inputs vary by platform.
Is there a universally safe load ratio?
No. Fixed acute-to-chronic workload ratio zones should not be treated as injury guarantees or alarms. Training history, the sport, recent breaks and how load is measured all matter.
How often should I review training load?
A weekly review is usually enough. Pay extra attention after illness, travel, a training break or a sudden change in volume or intensity.