Injury Prevention Through Workload Monitoring – Part 2

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This post is prepared by West 4th Physiotherapy associate Peter Francis

How do we manage load?

Once you understand that any stressor on the body is a training load you can start to manage it.  This means introducing the right amount of stress to elicit an adaptation to the tissues you are intending to train.  The first thing you need is a metric, or variable, to measure and monitor.  In baseball, for example, the number of high velocity throws is a good starting point to monitor a pitcher’s workload.  Tim Gabbett has performed a lot of the most recent work on various forms of workload monitoring in sport.  You can view more details of his work on his website.

We’ll use throwing as an example.  Most people don’t make the connection but throwing is an exercise and the more you throw the more proficient you become at it…to a point.  Throw too much and the working tissues risk entering the over-trained stage.  Throw too little and the working tissues will not adapt and withstand greater loads/workload volumes.  It’s all about the right balance and a logical progression.  Doing too little can be just as disadvantageous as doing too much.  Alan Jaeger is a prominent throwing coach and is a major proponent of throwing year round but that doesn’t mean he is saying to push max intensity for 365 consecutive days either.  He has some great summary information online.

The next piece of the puzzle is timing.  Tim Gabbett’s workload models are based off of the acute workload, chronic workload, and the acute:chronic workload ratio.  The terms were developed to create a model for monitoring workload of any individual who exercises.

Acute Workload

Summation measure of your workload metric over the course of a one-week period.

Chronic Workload

Rolling average of weekly summation metric over the course of four-week period.

Acute:Chronic Workload Ratio

Acute Workload Value ÷ Rolling Average (Chronic) Workload Value

With these values we can efficiently monitor workload both over the short term and long term.  It also enables us to compare short term workloads to longer term or average ones over a given period of time.  The take home concept is that when you see a spike in workload over a one week period compared to the average of the last 4 weeks you can perhaps infer that there is a higher risk of overuse or non-contact injury occurring.  The body can only perform at a level it is habitually accustomed to but that level can be trained and increased.  That being said, take too much time off and your level of physical capacity will decrease.

To simplify things we can just look at the ratio number.  The goal is to stay close to 1 (acute and chronic workload measure are equal).  We say “close to” because this means we are staying consistent with the load imposed on the body’s tissues.  There are times where we may want to be higher than 1 or slightly lower.  Where the ratio has been shown to be somewhat predictive of injury is when this ratio exceeds 1.5 or 2.  This means that the acute (1-week) workload has exceeded the average of the last four weeks by 50-100%!  It is surprising how often this happens with any activity yet we are still surprised when we get injured.  Keep the ratio in balance and you’ll stay healthy and keep progressing.

Peter-FrancisPeter Francis, Registered Physiotherapist
MPT, BKin, Dip. Sports Science

West 4th Physiotherapy Clinic
Main Street Physiotherapy Clinic

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