Acute:chronic workload ratio (ACWR)

What it is

The acute:chronic workload ratio compares how much you’ve trained recently with what you’re used to. It’s usually your last 7 days of load divided by your average weekly load over the last 28 days. A ratio of 1.0 means this week looks like your recent normal. Well above 1.0 means a spike.

Why it became popular

Research in team sports, summarised by Tim Gabbett in 2016, linked large, rapid jumps in training load with more non-contact soft-tissue injuries. It also found that high chronic load, built up gradually, seemed to be protective. ACWR became the best-known way to put that idea into a single number.

The debate

Later work challenged it. A 2020 analysis by Impellizzeri and colleagues argued that ACWR has statistical problems as a ratio, that no study had properly tested whether changing it changes injury rates, and concluded there’s no evidence supporting its use in load management systems to reduce injury risk.

The practical point most people agree on still stands: avoid big, sudden jumps in training load, and build up gradually. You don’t need a precise ratio to apply that.

How wearables measure it

Apple Watch’s training load feature works on a similar idea, comparing the intensity and duration of your workouts over the last 7 days with the previous 28 days, and rating your current load from well below to well above.

How P247 uses it

P247 doesn’t show an ACWR number. The weekly report looks at whether your load rose faster than your recovery signals.

This glossary is general information to help you understand your training data. It isn't medical advice, diagnosis or treatment. For injury, illness, medication, blood test results or any health concern, speak to a qualified health professional.

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