Acute:Chronic Training Ratio

Acute:Chronic Training Load (ACTR) is the ratio between training load over the previous 7 days (acute load) the average training load for the preceeding three 7 day periods (chronic load). Training load is measured using heart rate and duration data. This approach is a refinement of the 10% rule which runners have been using for years and which suggests that you should not increase training volume by more than 10% week on week.

Research suggests that when the ACTR gets higher than 1.3 the chance of injury begins to significantly increase. When training load drops significantly then detraining can occur.

More information

http://bjsm.bmj.com/content/early/2016/01/12/bjsports-2015-095788