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How hard the whole session felt, rated once, about half an hour after finishing.
420 AU
60 minutes at an RPE of 7
That ratio sits inside the band the 2016 paper proposed (0.8 to 1.3). Read the next paragraph before you act on it.
The acute:chronic workload ratio is disputed, and this page will not pretend otherwise. It was proposed in Gabbett, Br J Sports Med 2016 and has been challenged on its arithmetic since: Lolli and colleagues (2019) showed that including this week inside its own four-week average couples the two halves of the ratio and manufactures correlation, and Impellizzeri et al, Int J Sports Physiol Perform 2020 found no evidence supporting its use for managing injury risk — the same group showed that a random chronic load predicts injury about as well as the real one. A 2025 meta-analysis in BMC Sports Science, Medicine and Rehabilitation did find the lowest injury rates inside that band across 22 cohorts, then reported heterogeneity above 75% and a confidence interval too wide to call the band safe. Both numbers are shown above; neither is a rule.
Session load itself is on firmer ground: duration in minutes multiplied by a whole-session rating of perceived exertion, from Foster and colleagues (2001). The units are arbitrary, so the number is only meaningful against your own previous weeks — never against someone else’s. Foster’s method also defines monotony, the week’s mean daily load divided by its standard deviation, and strain, the weekly load multiplied by monotony; both need a figure for every day rather than a weekly total.
Foster and colleagues published the session-RPE method in 2001 and it remains the standard low-cost way to quantify a training session: take the minutes you trained, multiply by a single rating of perceived exertion for the whole session on a nought-to-ten scale, and record the product. Ninety minutes at a seven is 630 arbitrary units. The rating is collected once, after the session has settled — roughly half an hour later — rather than during it, so a brutal final set does not colour the whole entry.
The number has no physical meaning and does not transfer between people. Two athletes reporting 630 have not done comparable work; they have each described their own session against their own internal scale. What the figure is good for is your own trend — this week against the last month, this block against the last one — and it is worthless as a comparison with anybody else, including a training partner doing the identical programme.
The same method also defines monotony, the week’s mean daily load divided by its standard deviation, and strain, the weekly load multiplied by monotony. Both need a figure for every day of the week rather than a weekly total, which is why they are described here but not calculated.
The acute-to-chronic workload ratio divides the most recent week by the average of the last four. Gabbett proposed it in 2016 and suggested keeping it between 0.8 and 1.3, and it spread quickly into apps and wearables as though it were a speed limit. It is not settled science, and this page will not present it as such.
Lolli and colleagues showed in 2019 that including the current week inside its own four-week average couples the numerator to the denominator and manufactures correlation out of arithmetic alone. Impellizzeri and colleagues went further in 2020, finding no evidence supporting its use for managing injury risk, and demonstrated that a randomly generated chronic load is associated with injury about as strongly as the real one.
The defence is not empty either. A 2025 systematic review and meta-analysis in BMC Sports Science, Medicine and Rehabilitation pooled twenty-two cohort studies and did find the lowest injury incidence inside that same band — then reported heterogeneity above 75%, noted that four fifths of the evidence comes from soccer, and gave the band a confidence interval too wide to call it safe. So the ratio is shown here computed both ways, coupled as originally defined and uncoupled with the current week removed, without a colour telling you which value is good.
No. That threshold comes from one 2016 paper whose statistical basis has been challenged repeatedly since, and treating it as a stop sign gives a contested number more authority than the researchers who published the critiques would allow. Use it as one prompt to look at a week that jumped, not as an instruction.
Because the difference between them is the criticism made visible. The coupled version puts this week inside the average it is being divided by, which guarantees some correlation regardless of the athlete; removing it gives a comparison against genuinely prior weeks. Seeing both makes clear how much of the ratio is arithmetic.
Only roughly, and that is the method’s main weakness. Perception drifts with mood, sleep, caffeine and how recently you were last humbled by a session. Rating consistently matters more than rating accurately, and a fortnight of ratings is more informative than any single entry.
Yes, and that portability is why the method caught on: it needs a clock and a scale rather than a heart rate monitor or a GPS unit. Do bear in mind that an hour of heavy lifting and an hour of intervals producing the same number are not the same stress on the same tissue.