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Training Load Calculator (ACWR)
Acute:Chronic Workload Ratio — based on Gabbett (2016). Identify your injury risk zone before your next training block.
⚠For reference only. ACWR is a research tool (Gabbett 2016), not a clinical diagnostic. Individual response to training load varies. Consult a sports physiotherapist for personalised advice.
1.14
Optimal training zone
Acute: 80 km · Chronic avg: 70.0 km/wk
Sweet spot — chronic workload is building and acute load matches it well. Lowest injury risk.
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ACWR reference zones
| ACWR | Zone | Risk |
|---|
| < 0.8 | Undertraining | Deconditioning |
| 0.8 – 1.3 | Sweet spot | Low |
| 1.3 – 1.5 | Caution | Elevated |
| > 1.5 | Danger zone | High |
Source: Gabbett TJ (2016). The training–injury prevention paradox. British Journal of Sports Medicine, 50(5), 273–280.
Frequently asked questions
What is the ACWR and what does it measure?
ACWR (Acute:Chronic Workload Ratio) measures how this week's training load compares to your recent fitness base. Acute load = last 7 days of training. Chronic load = 28-day rolling average divided by 4 (to get a weekly average). ACWR = acute ÷ chronic. A ratio of 1.0 means you trained exactly as much as your average. Above 1.0 is a load spike; below 1.0 is easier than usual.
What is a safe ACWR range?
Research supports 0.8–1.3 as the lowest injury risk range. This is often called the "sweet spot" or "optimal training zone." Below 0.8 suggests undertrained or detraining. Between 1.3–1.5 is elevated risk — monitor carefully. Above 1.5 is the danger zone associated with significantly higher injury risk.
What happens if my ACWR is above 1.5?
A ratio above 1.5 means your acute load has spiked well beyond your chronic base. Research (Gabbett, 2016) found athletes in this zone had 2–4× higher injury risk. The recommended response is to reduce training volume or intensity for the next 5–7 days to let your chronic baseline "catch up." Avoid adding more high-intensity sessions until the ratio drops below 1.3.
How do I calculate sRPE (session RPE)?
After each session, ask yourself: how hard was that overall, on a scale of 1 to 10? Multiply that number by the session duration in minutes to get Arbitrary Units (AU). Example: a 45-minute run that felt like a 6 out of 10 = 270 AU. Sum all AUs for the last 7 days to get acute load. Sum the last 28 days and divide by 4 to get chronic weekly average.
Can I use ACWR for cycling or swimming?
Yes — ACWR works for any endurance sport. For cycling, km or hours are common. For swimming, metres or hours. For sports mixing intensity levels (intervals + easy rides), sRPE × minutes (AU) is more accurate than distance or time alone because it weights intensity. The key is consistency: use the same metric for every session, every week.
How long do I need to track training before ACWR is reliable?
You need at least 4 weeks of consistent data to have a valid chronic baseline. The first few weeks of calculation will be less reliable. After 8 weeks your baseline becomes much more stable. Some coaches recommend a 6-week minimum before making training decisions based on ACWR numbers.
Does ACWR predict injury?
ACWR is associated with injury risk at the group level in research studies, but it does not reliably predict injury for any individual. Many athletes train above ACWR 1.5 without injury; others get injured well within the sweet spot. It is best used as a warning signal — if your ACWR spikes above 1.5, consider recovering rather than adding load, but combine it with subjective feel, sleep quality, and resting heart rate for a fuller picture.