Training-Stress Balance

Load Management For Injury Prevention

Managing training load is crucial in injury prevention and treatment. A graphic in Tom Goon’s recent blog visualises how training load outweighs all other factors.

Historically we have advised that training loads shouldn’t increase by more than 10% a week. I’m not sure where this number comes from. I’ve got no problem with it, it seems reasonable, and I’ve quoted it hundreds of times.

There’s a 2015 BJSM podcast interview with Tim Gabbett on load management for injury prevention. Specifically Tim talks about this paper:

Spikes in acute workload are associated with increased injury risk in elite cricket fast bowlers 
- Billy T Hulin, Tim J Gabbett, Peter Blanch, Paul Chapman, David Bailey, John W Orchard, 2013.

It is research into fast bowlers, but I think the principles apply just as well to any athlete.  

The authors measured the acute workload of the last 7 days (and call it “fatigue”) and compare that to the chronic workload of the previous 4 weeks (which they call “fitness”).

Measuring Training Load

For runners, if the training is reasonably homogenous, we could most simply measure the workload as the total kms/week.  

Or we could be more accurate and account for a mixed training program that may include a variety of hills / sprints / cross training etc, by giving each session a rate of perceived exertion (RPE) out of 10, and multiply that score by the number of training minutes:

Training load = session RPE x duration (minutes)

This is called a Foster’s Score, and provides a simple method for quantifying training loads from a variety of different training modalities.

The research subtracted the current one-week average from the previous 4-week average and called this number the “training-stress balance”.

A negative training-stress balance increases the risk of injury by 4 times.

So:

[Last 7 days’ session RPE x duration (minutes)] - ([Last 4 weeks’ session RPE x duration (minutes)] / 4) = TRAINING-STRESS BALANCE

Negative balance = 4 times risk of injury

Essentially this formula means you shouldn’t increase your training load by more than 25% a week.

For people that may be more vulnerable to injury I would change the 4-week average to a 6-week average, therefore, bringing the increase in load each week down from 25% to 16%.  

This more cautious group could include: 

• Pre-season training
• Kids going through growth spurts
• Athletes returning from injury
• Known history of over training injuries
• People without any training history
• Novel exercise modality