The acute:chronic workload ratio revolves around acute and chronic workloads and how they affect your players fatigue levels.
Acute workload is the rolling average of the last 5 - 14 days (footy can use 7 days) and represents your level of fatigue.
Chronic workload is the rolling average of the last 4 - 6 weeks (footy can use 4 weeks) and represents your level of fitness.
All workload is determined via workload (distance ran/weight lifted etc) / rate of perceived exertion (rpe).
The basic premise is that if you increase acute loading too quickly, and too far over your acute:chronic workload ratio, you'll more than likely suffer from fatigue related issues i.e INJURY!
Here a few numbers to give you a look at it.
The last 4 weeks you've done 1 run for 30mins each week:
- 30mins (time) x 8 (rpe) = 320 (load) x 2 runs = 640 (load)
- 30mins (time) x 7 (rpe) = 280 (load) x 2 runs = 560 (load)
- 30mins (time) x 7 (rpe) = 280 (load) x 2 runs = 560 (load)
- 30mins (time) x 6 (rpe) = 180 (load) x 2 runs = 360 (load)
Total Loading = 1,610 units
As you can see the same run got gradually easier (relatively) pretty much each time it was repeated.
All good so far for chronic loading.
Last week footy training started so you did 2 nights there + another 2 runs on your own:
- Footy Training x 90mins x 9 rpe = 810 (load)
- Footy Training x 90mins x 10 rpe = 900 (load)
- 30mins x 7 (rpe) = 280 (load) x 2 = 460 (load)
Total Loading = 2,270 units
Hmm quite a big week when you see the numbers.
The first footy training was pretty hard not 100% as you were fresh off the break.
2 days later you had footy training but you were still sore and tired from day 1 and even though the training was pretty much the same, the fatigue present in your system made everything else harder than normal and it pretty much pushed you to the brink.
A few days later you decide to "run it out" but again fatigue was still present from the 2 footy training days and thee same run that was a 6 rpe last time, shifted up to a 7.
The second run also registered a 7 rpe from the weeks fatigue build up.
What we're left with is an acute loading of 2,270 units and a chronic loading of 1610 units.
Now let's look at what the results can tell us.
A ratio of about 1.3 is the sweet spot where this week you've performed 1.3 x what your chronic loading is.
In this case we have 1610 x 1.3 = 2093 units
As you can see this player's workload reached 2,270 units which is actually an a:c ratio of 1.41
What are the implications from this you ask?
A spike of 1.5 and higher is what has been determined to be related to SIGNIFICANT INJURY RISK.
In week 1 this player has already reached 1.41 of his maximum 1.5 loading ratio and as the training ramps up, if his fitness doesn't come along at a greater rate then his fatigue build up, they're in trouble by February, if they make it that far.
A the very top end (probably not what us local/amateur types need to be worried about) you're 50 - 80% more likely to sustain an injury with a training load of 3000 - 500 units but to stay on the safe side and reduce any potential soft tissue injuries aim for a ratio of .8 and build up to 1.3 over time, not increasing loading by more than 10% for any given week.
The injury will come 7 - 10 days after a spike in load and can come as late as 21 - 28 days.
As a player you need to maintain a minimal chronic workload at all times, especially on breaks.
As coaches you need to have this in the back of your mind when deciding what types of drills you run and then what running work you add on top of that.
You also need to know the players that do extra training and grouping your players can also help you run the drills to the loading that they need.
Thanks to Mladen Javanovic and Tim Gabbett.
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