ACWR (Acute:Chronic Workload Ratio) is the rolling 7-day acute training load divided by the rolling 28-day chronic training load. Acute represents what the athlete is absorbing right now; chronic represents what they have adapted to.
The ratio is dimensionless: any consistent measure of daily load (session-RPE × duration, GPS distance, PlayerLoad) works as long as both windows use the same unit. The commonly cited "sweet spot" is 0.8–1.3; below is under-training, above is an acute spike vs. baseline that has been associated with elevated injury risk in some research.
Use ACWR as a flag for a conversation, not a hard decision rule. The original Gabbett threshold has been challenged on methodological grounds (Impellizzeri 2020) — overlapping window math creates spurious associations. A high ratio is a prompt to check wellness, sleep, and weekly plan, not an automatic reason to pull the athlete.
Where it's used
Team-sport load monitoring (soccer, rugby, basketball, field hockey), military readiness screening, return-to-play progression.
References
- Gabbett TJ (2016). The training–injury prevention paradox. Br J Sports Med.
- Impellizzeri FM, Woodcock S, Coutts AJ, et al. (2020). What role do chronic workloads play in the acute to chronic workload ratio? Sports Med.
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