{"id":500,"date":"2026-08-01T17:28:52","date_gmt":"2026-08-01T16:28:52","guid":{"rendered":"https:\/\/mytrainingforecast.run\/blog\/?p=500"},"modified":"2026-08-01T17:28:54","modified_gmt":"2026-08-01T16:28:54","slug":"acwr-running-injuries","status":"publish","type":"post","link":"https:\/\/mytrainingforecast.run\/blog\/acwr-running-injuries\/","title":{"rendered":"ACWR for runners: Which injuries it can (and can’t!) predict"},"content":{"rendered":"\n

Somewhere in the last fifty years, running acquired a rule: “Don’t increase your weekly mileage by more than 10 %<\/em>“. The 10 % rule gets mentioned all the time, but nobody is quite sure where it came from. It sounds sensible, easy to remember and to calculate. But the 10 % rule has 0 % scientific evidence going for it, quite worse in fact: almost 20 years ago a randomised control trial concluded that the 10 % rule makes no difference whatsoever to prevent running injuries (Buist et al. 2008).<\/p>\n\n\n\n

So when something better arrived, the running world was ready for it. Blanch & Gabbett proposed the Acute:Chronic Workload Ratio (ACWR) in a series of 2015 papers, and it was almost immediately incorporated into an International Olympic Committee consensus statement about training load management and risk of injury (Soligard et al. 2016). Millions of athletes have now had training decisions made for them on the strength of that number.<\/p>\n\n\n\n

The ACWR compares your recent running against what you’re used to. Quick example, let’s say you’ve been running 20 km per week for a while, and decide to add one more 5k run this week. That would look like:<\/p>\n\n\n\n

Week 1<\/strong> (this week)<\/em><\/th>Week 2<\/strong> (last week)<\/em><\/th>Week 3<\/strong><\/th>Week 4<\/strong><\/th><\/tr><\/thead>
25 km<\/td>20 km<\/td>20 km<\/td>20 km<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\nTo work out your ACWR:
\n
    \n
  1. Add up your last 7 days of running, that’s your Acute Training Load (ATL)<\/strong><\/li>\n
  2. Average your last 4 weeks, that’s your Chronic Training Load (CTL)<\/strong><\/li>\n
  3. Divide ATL by CTL to get your Acute:Chronic Workload Ratio (ACWR)<\/strong><\/li>\n<\/ol>\n\n\n\n

    <\/p>\n\n\n\n

    From this example we get:
    ATL = 25 km<\/strong>
    CTL<\/strong> = (25 +20 +20 +20) \/ 4 = 21.25 km \/ week<\/strong>
    ACWR<\/strong> = 25 \/ 21.25 = 1.18<\/strong><\/p>\n\n\n\n

    The appeal is obvious: it accounts for fitness accumulated over several weeks, not just last week, and a body of research put injury numbers on it:<\/p>\n\n\n\n