What this number does and doesn’t tell you
The acute:chronic workload ratio compares your most recent week of training against your 4-week average. It’s a widely used way to spot sudden load spikes, which are one of several known contributors to non-contact injury risk. It is not a diagnosis, and a ratio in the “Optimal” range doesn’t guarantee you won’t get injured, just as a high ratio doesn’t guarantee you will. The methodology itself has real, published critiques (see the FAQ below) — this is a pattern-spotting tool, not a verdict.
How to track your weekly load
The simplest widely-used method is session-RPE: rate each session’s overall difficulty from 1-10 (RPE), multiply by the session’s duration in minutes, and sum every session across the week. It works for lifting, running, team sports, or mixed training, since it’s based on perceived effort rather than a sport-specific metric like pace or tonnage.
Frequently asked questions
What is the acute:chronic workload ratio?
It's a way of comparing how much you've trained this week (acute load) against what you're conditioned for based on the last 4 weeks (chronic load). A ratio near 1.0 means this week is typical for you; a ratio well above 1.0 means this week is a significant spike relative to your recent history.
Is ACWR scientifically proven to predict injuries?
It's genuinely debated. The original research found the 0.8-1.3 range associated with lower injury rates in some sports, but later methodological critiques pointed out that because acute load is mathematically part of chronic load in this rolling-average model, some of that correlation can be a statistical artifact rather than a pure physiological signal. Treat ACWR as one input alongside how you actually feel, not a verdict.
What counts as "training load"?
Most commonly, session-RPE: multiply a session's duration in minutes by your perceived effort for that session on a 1-10 scale (RPE), then sum every session in the week. A 45-minute run at RPE 6 is 270. Add up all sessions for the week to get your weekly total. Any consistent metric works, as long as you use the same one every week.
What should I do if I land in the "High risk" zone?
First check whether the spike was intentional (a planned peak week, a race, a one-off event) or accidental. If accidental, consider whether the following week should be lighter to let your chronic average catch up. This tool flags the pattern; it can't tell you whether the specific spike was appropriate for your situation.
How often should I check this?
Weekly is typical — recalculate once you've logged a full new week of training. Checking more often than that just re-measures the same underlying trend with more noise.