Updated: Feb 11, 2021
The other day, I was having a great discussion with Physical Therapy and Performance interns and asked if they knew what the Acute to Chronic workload ratio was and how it related to injuries.
The bad thing was that none of them knew what it was or even the basic premise.
So, let’s see if we can break it down into simple terms:
WHY IS THIS CONCEPT SO IMPORTANT?
The importance of understanding how the Acute:Chronic workload ratio works is that most (if not all) noncontact injuries occur due to an acute spike in workload during exercise or activities of daily living.
Basically, this means that the load placed on the body is more than the capacity that the tissues are trained to handle.
Tennis player who generally plays once or twice a week on a recreational level has no apparent shoulder pain during current matches or daily life. However, they decide that they are going to play in a tournament involving four matches in a weekend and then play another match two days after the tournament. After their last match they have an onset of shoulder pain that prevents them from lifting overhead and playing tennis. Most likely, this sudden increase in their volume of playing tennis (5 matches in 4 days) exceeded their normal playing volume (2 matches every 7 days) which caused for their body to not be prepared to handle the load on that specific body part – causing an injury.
The good thing is that if you manage your training load and frequency properly then there is a high probability you will not miss that next tennis match. The bad thing is that these situations happen more than you think.
SO HOW DOES THIS WORK?
The easiest way to understand the concept and calculation is to use numbers.
The numbers that I will use in this example is the mileage that a long-distance runner would accumulate.
If you are a runner, your chronic workload is the average of your last four weeks in running volume and your acute workload would be your current week’s mileage.
Week 1: 20 miles
Week 2: 23 miles
Week 3: 21 miles
Week 4: 25 miles
Chronic Workload: 22.25 miles
Acute Workload: 15 miles
Acute:Chronic Workload Ratio = 25 miles (Acute) / 22.25 miles (Chronic) = 1.12
<0.80 = under training and higher relative injury risk
.80 – 1.30 = optimal workload and lowest relative injury risk – “Sweet Spot”
> 1.50 = “danger zone” and highest relative injury risk
Note: These numbers do not apply to every sport and every athlete but offer a general guideline in monitoring
So, what is the great thing about working out and playing more often? Higher chronic workloads have been shown to be injury resistant as long as acute loads do not exceed ratios over 1.3 – when they do, higher chronic workloads tend to be more causative of injury
Now, back to the tennis player from earlier – MORE NUMBERS!
Week 1: 6 sets
Week 2: 5 sets
Week 3: 6 sets
Week 4: 11 sets
Acute to Chronic Workload Calculation: 11 sets (acute) / 7 sets (chronic) = 1.57 or “danger zone”!
As you can see, this definitely can lead to an injury or at the very least, pain that can limit your ability to play.
SO WHAT DO WE DO WITH THIS KNOWLEDGE TO HELP WITH INJURIES?
The best piece of info to take from this is to make sure that you gradually train and progress your time playing a sport or performing a certain exercise.
What if you do get an injury? Too often, athletes are told they should stop doing an activity all together as they “recover” or seek treatment. However, this mode of thinking can contribute to - or actually prolong - their injury.
Instead of taking weeks off, slowly progress back into your activity. Play as much as you can without increasing your pain.
Slowly building capacity is a better choice than taking weeks off and throwing off your ratios all together.
This is one of the most important things to consider when returning from an injury or a long break in training. Train smarter, not harder, and be mindful of these factors as your build capacity!
Remember the following when training:
Load > Capacity = INJURY
Capacity > Load = PREVENTION
By gradually progressing our activity, avoiding spikes in training or playing our sport and listening to our bodies, we can improve our capacity to move and reduce our chance of injury!
If you have any questions please reach out and let me help you better understand!