Acute to Chronic Workload Ratio and a Simple Approach to Tracking

What is ACWR?

Acute to Chronic Workload Ratio (ACWR) is a interesting topic that can shed light on how overuse injuries occur. It describes how much activity you are currently doing compared to how much activity you have been doing. Most people have been through the process of starting a new gym or running program, doing too much too soon, and within the first month burning out or getting injured. If you are just getting back into training and looking to safely increase your load this can be very important information in preventing an overuse injury.

Typically, ACUTE workload is everything you have done over the past week, while  CHRONIC workload is everything you have done over the past 4 weeks. The current research shows that if your ACUTE workload is greater than 1.5 x your CHRONIC workload (average over the previous 4 week span), you have a increased likelihood of sustaining a injury during a workout or physical activity. This does NOT mean you will injure yourself; however, it is a tool to help reduce the likelihood of a injury due to not programming enough recovery time or programming to much load.  Ideally, you would like your workload ratio to be between 0.8 and ~1.3. This has been termed the ‘Sweet Spot’ because you are providing enough of a stimulus for change without entering the ‘Danger Zone’.

Tracking your ACWR

Tracking ACWR can be very difficult but the easiest example I can give is with someone who is a runner:  If you run a total of 10 miles a week for 4 weeks, your average is…10 miles/week. Easy enough.  If the following week you want to increase your training load and decide to run anything over 15 miles, your injury risk increases (15 divided by 10 equals 1.5). In this example, you would want to limit the current weeks training to 13 miles to keep you in the Sweet Spot. The next week your CHRONIC workload would jump up to 10.75 miles (10 + 10 + 10 + 13 divided by 4 weeks). That would take your new ACUTE workload (1.3 x 10.75) to about 14 miles (13.975 miles); you would then keep repeating the process.

This sounds nice and easy for runners, but what if you are a Cross-fit athlete, a recreational weight lifter, or a high school athlete who spends a mix of time on the field and in the weight room? This is where it can get tricky. There are equations and different techniques that are used to specifically track your ACWR based on sets, reps, and load. However, that takes a lot of time and effort. A simple approach, that I believe can give you useful data, is workout duration multiplied by rate of received exertion (RPE). Workout duration is simply how many minutes you exercised. Rate of Perceived Exertion is how hard you thought workout was on a scale of 1-10. RPE is very individualized to each person, but if you are consistent on how you are rating your workouts, it can be very accurate. When using this method I typically like my athletes to wait till the following morning to give their RPE. Immediately following a workout it is sometimes harder to give a accurate measure based off of recency bias.

A daily example could look something like — Timmy performed a 20 minute AMRAP at Cross-fit that was a 7/10 on the difficulty scale (RPE). You would then use the equation above to get 20 x 7 = 140 (we can call this daily strain). Let’s say he worked out 2 more days that week for 30 minutes at a 6/10 and for 20 minutes at a 8/10. His ACUTE workload for the week would be 140 + 180 + 120 = 440. You would compare that 440 to the 4 weeks average leading up to that week. There are a couple apps that can track this information for you or you can simply put it into a excel spreadsheet.

I really like to use ACWR combined with Heart Rate Variability (HRV) to track my own “Readiness to Perform.” HRV is another interesting topic that I will hopefully write about in the future. I am currently using the HRV4Training app, which will use my HRV score with my subjective history (including ACWR) to determine if it is a good day to proceed as planned, limit activity, or rest. There are a couple other apps that measure HRV, as well as wearable devices, so you might want to do some research before choosing one.

Like I mentioned above, there are many options to track your ACWR. This was meant to be a simple introduction for those wanting a way to stay on top of their training. If anyone has any questions or would like to discuss this topic further please feel free to comment below or reach out.

Thanks and I hope this was helpful!