Acute:Chronic Workload Ratio: How to Manage Your Training Load

Most endurance-sport injuries are not caused by a single hard session, but by load that has risen too fast. The acute:chronic workload ratio — ACWR for short — makes exactly that visible: it compares what you are training this week with what your body was used to over the last few weeks. Used correctly, it is a simple early-warning system against overload.

What is the acute:chronic workload ratio?

The ACWR puts two time windows in relation: the acute load (typically the average of the last 7 days) and the chronic load (the rolling weekly average of the last 28 days). The idea behind it: chronic load represents what your body is currently built for — tendons, bones, metabolism and the cardiovascular system adapt over weeks, not days. Acute load is what you are asking of it right now.

When both sit close together (a quotient around 1.0), you are moving within familiar territory. When acute load jumps well above the chronic level — after a training camp, a “catch-up week” or an ambitious start to a new season — the statistical risk of overload complaints and injuries rises. The ACWR makes exactly that jump tangible as a number.

How to calculate your ACWR

The formula is simple: ACWR = acute weekly load ÷ average weekly load of the last 4 weeks. The critical step is choosing the load measure:

• sRPE (session RPE): training minutes multiplied by perceived exertion on a 1–10 scale. 60 minutes at RPE 6 gives 360 units. Works without any technology and is surprisingly valid.
• TSS (Training Stress Score): load derived from heart-rate or power data — objective and comparable across sports. How TSS is calculated is explained in the article on the Training Stress Score.
• Kilometres or elevation: possible, but blind to intensity — 30 easy kilometres weigh differently from 30 kilometres of intervals. A fallback only.

Worked example: Your last four weeks came in at 3,200, 3,400, 3,100 and 3,300 sRPE units — chronic load of 3,250. This week you have 4,100 units planned. ACWR = 4,100 ÷ 3,250 = 1.26. Ambitious, but still inside the safe range. At 5,000 units the ACWR would be 1.54 — clearly in the risk zone.

The sweet spot: 0.8 to 1.3

Team-sport research (notably Gabbett 2016) established a widely used guideline:

• Below 0.8: You are training well under your habitual level — sensible in deload weeks and during tapering, but over time you lose the adaptation your chronic load rests on.
• 0.8–1.3: The “sweet spot”. Load rises moderately (or falls in a controlled way) and the body's adaptation rate keeps up. For long-term building, values around 1.1–1.25 are considered productive.
• 1.3–1.5: Grey area. Single weeks here are fine — a training camp, for instance — but not several in a row.
• Above 1.5: Risk zone. Weekly load sits 50 % above the accustomed level; in the studies, injury risk in the following week rose markedly.

Important: the ACWR says something about load spikes, not absolute hardness. Someone training constantly at a very high level shows a “pretty” ACWR around 1.0 — and can still drift towards overtraining if recovery does not keep up.

In practice: finally replacing the 10-per-cent rule

The old rule of thumb “never increase volume by more than 10 % per week” is a special case of the ACWR: train the same every week, add 10 %, and you land at roughly 1.1. But the ACWR is more flexible and more honest, because it includes the trend of the last four weeks:

• After an easy week, +10 % can already be too much — because chronic load has dropped. The ACWR shows this; the 10-per-cent rule does not.
• After an excessive week, the next week may well sit 20 % below the previous one and still make sense (deload week, ACWR around 0.8).
• Returning after a break: after two weeks of holiday your chronic load is nearly halved. “Just training as usual” then produces an ACWR of 1.8 and more — the classic moment for strains and irritations. Better: ramp back up over two weeks at 60–70 % of the old level.

In practice this means: plan your weekly load so the ACWR stays between 1.05 and 1.25 in build weeks and falls to 0.7–0.85 in deload weeks. That automatically gives you a sensible periodization with a wave structure — without having to design one deliberately.

What such a wave looks like concretely: baseline 3,000 units per week. Week 1: 3,300 (ACWR 1.08). Week 2: 3,550 (1.11). Week 3: 3,800 (1.12). Week 4: deload at 2,400 units (0.69) — deliberately below the sweet spot, because this is where the adaptation of the three build weeks happens. The next block then starts on a higher level: chronic load has climbed to about 3,300, so week 5 may begin at 3,600 without breaking 1.3. Over twelve weeks that adds up to an increase from 3,000 to roughly 3,800 units — more than 25 % extra training capacity, without a single week spent in the risk zone.

The limits of the ACWR — what the number does not see

The ACWR is useful, but it is no oracle. Three blind spots are worth knowing:

• It is scientifically debated. The classic 7:28-day split with simple rolling averages has been criticised in the methods debate; exponentially weighted models (EWMA) describe adaptation and detraining more realistically. The 0.8–1.3 zones are rules of thumb, not laws of nature.
• It ignores composition. Two weeks with identical load can feel entirely different: 80 % easy plus two hard sessions is not the same as seven days of grey-zone grinding. Intensity distribution along the 80/20 principle remains a task of its own.
• It ignores non-training stress. Sleep deprivation, work stress and nutrition change how much load you can tolerate. It pays to also watch your heart-rate variability as a recovery indicator.

Common mistakes in load management

• The catch-up trap. A missed week gets “made up” by doubling the volume — ACWR beyond 1.8. Expired training is expired; the plan continues from today, not retroactively.
• A training camp without a follow-up easy week. After a high-load camp week, the next week must be markedly quieter — otherwise the bill arrives exactly when the body wants to cash in the adaptation.
• Playing the number off against how you feel. An ACWR of 1.2 “permits” nothing when your mucous membranes, shin or sleep are already striking. The ACWR is a traffic light, not a blank cheque.
• Adding load across sports incorrectly. Running stresses tendons and bones more than cycling at the same sRPE. Multisport athletes should weight the running share slightly higher in the calculation.

How Peakora manages your load

Peakora uses the same underlying principle, but with the more modern toolkit: instead of rigid 7:28 quotients, the form monitor works with exponentially weighted load and fatigue values (CTL/ATL) and turns them into your daily form (TSB). The engine plans weekly load so that jumps beyond the accustomed level are avoided — build weeks rise moderately, every fourth week is a deload. When the recovery monitor detects declining form or poor recovery, adaptive planning moves the next hard session before the ACWR even becomes a problem.

Frequently asked questions about the ACWR