ACWR and its limits for self-tracking

The acute:chronic workload ratio divides recent load, often one week, by an average over previous weeks. Load might mean distance, minutes or a combined measure. The answer changes with the definition and time window.

A sudden rise can prompt a review of training changes. It cannot tell whether one person will definitely be injured.

Impellizzeri and colleagues describe methodological problems with using ACWR to recommend injury prevention; a causal link has not been established. Do not use a single threshold as a hard train-or-rest rule.

Track overall load, sleep, pain and life context. When symptoms appear, seek appropriate assessment instead of trusting a reassuring ratio.