A beginners guide to what acute : chronic workload is and why it is important.

Today I ran on tired legs. I had thoughts of not running and just making up the km’s later. But then I remembered that my chronic workload would suffer… And therefore my acute:chronic workload ratio would be skewed… What is an acute:chronic workload ratio and why is it important? Glad you asked…!

Firstly, workload refers to how much work our tissues do over a given time period. We can use any number of variables to measure it such as speed, duration, frequency, repetition number, rate of perceived exertion and in the case of this piece, volume, and more specifically, number of kilometres in a week. The two aspects of workload we are interested in in this case are acute workload and chronic workload.

Acute workload most commonly refers to the amount of loading completed within a given week of training. Whereas a chronic workload refers to the average workload each week over the four weeks. These time frames can be easily modified to suit your training needs.

Let’s use the following example of a runner’s first month of training. This runner has completed 3km, 4km, 4km and 5km over the first four weeks. In their fourth week, their chronic workload can be measured at 4km (the average of the 4 weeks). Their acute workload in that 4th week is 5km. The important value is the ratio of these two numbers – or the acute:chronic workload ratio. To work this out we divide the acute workload (5) by the chronic workload (4) to give us our ratio of 1.25.

So that is the what. The why is always much more interesting.

Many researches have found that a ratio of between 1.0-1.25 is effective at protecting athlete’s against injury (Gabbett, T., 2016). When the ratio lifts above 1.5 we have a threefold chance of injury as to when it is below 1.0. However, when the workload sits between 1.0 and 1.25 we actually have about a quarter of a chance of injury as to when it sits below 1.0 (Malone, et al., 2016). Put simply, if we control our workload by not creating spikes or troughs in volume, we are able to significantly reduce our risk of developing an injury.

The key to avoiding these spikes and troughs is planning and consistency. An easy way to plan our workloads for an upcoming event is to plug them in to an excel document. From there you are able to generate the average of the four weeks (your chronic workload) and compare it to your acute workload, to generate your ratio.

Use the codes below to help you get the average:

=AVERAGE(A1:A4)

This takes in to account that you started the first week in the box A1 and went downwards.

=A4/B4

This takes in to account that you placed the chronic workload for the fourth week in B4.

Here is an example of one that I have produced for an 8km goal with a 12 week training period:

Obviously there are many other variables to your training other than volume, but this is a really easy and effective place to start to avoid those unnecessary injuries that so many runners experience early in their training plans.

References:

 Gabbett, T. (2016). The training-injury prevention paradox: should athletes be training smarter and harder? BJSM, 0, 1-9. doi:10.1136/bjsports-2015-095788

 Malone, S., Owen, A., Newton, M., Mendes, B., Collins, K. & Gabbett, T. (2016). The acute:chronic workload ratio in relation to injury risk in professional soccer. J Science and Medicine in Sport, 0.