Load Monitoring in Hockey: Using Gabbet's Acute-Chronic Workload Ratio

Injuries will occur in sports, but one of our main responsibilities as performance coaches involves twofold:

1) Mitigating the risk of injury.

2) When an injury happens, prepare athletes so they don't get reinjured.

As you can see in the image below, the NHL's healthiest teams tend to win more as well.

Coaches may fear that higher on-ice training loads cause higher injury rates due to overtraining.

However, the truth is that both undertraining and overtraining can cause injury. There's a “sweet spot” where we can optimize performance potential and minimize fatigue.

The goal is to not always do less in fear of overtraining. Then athletes won't be prepared for the demands of the game, causing decreased performance and increased injury risk.

What is “Training Load?”

There are two different types of training load – external training load and internal training load. External training load is the physical work an athlete performs (i.e., distance run, time spent at different velocity zones, etc.) while internal training load is the within-training response to the physical work (i.e., perceived exertion, time spent in different heart rate zones, etc.).

(Editor's Note: for an entire presentation on internal vs external load, check out this webinar with Dr. Steve McGregor.)

While understanding training loads is necessary, we must also realize that different athletes will respond differently to the same internal and external training loads.

For example, if we look at an elite marathon runner versus a high school 100-meter sprinter, these two athletes will be able to handle completely different volumes and intensities of the different forms of training.

One athlete's average might be another athlete's easy.

Tim Gabbett and the Acute-Chronic Workload Ratio

Tim Gabbett's research has become very popular in the world of team sports over the last 10 years. One of his most popular models, the acute-chronic workload ratio, has been used by many, including myself, and found great success.

Acute timelines can be as short as one session, but are typically considered as one week of training.

Chronic timelines are the rolling average of multiple previous weeks but are typically considered as the previous four weeks of training.

These timelines are, and should be, variable based on the sports schedule.

Acute training loads should be viewed as the state of “fatigue” while chronic training loads should be viewed as a state of “fitness.”

If the acute training load is low, the athlete will experience minimal fatigue.

Inversely, if the acute training is high, the athlete will experience high levels of fatigue.

The same can be seen with chronic training loads. If the chronic training load is high, the athlete will have developed high levels of fitness, but if chronic training load is low, fitness levels will drop, and athletes won't be prepared.

From here, the acute-chronic ratio is just simple math. If the acute load is greater than the chronic load, the ratio exceeds 1.0. If the acute load is less than the chronic load, then the ratio drops below 1.0.

Gabbett found that acute-chronic workload ratios within the range of .8-1.3 should be considered the “sweet spot” where injury risk is the lowest, while injury risk was the highest when the ratio exceeded 1.5.

This is unfortunately where a lot of people have misinterpreted his data, in my opinion.

Coaches see that an acute-chronic ratio above 1.5 increases injury risk, they have adopted a “less is more” strategy. While this is well-intentioned, by continuing to do less and less, chronic loads consistently go down, bringing fitness along for the ride.

Training Load's Effect on Performance

While doing too much work compared to what's “normal” can cause injury, we also need to be cognizant of how it affects on-ice performance.

A study out of Australia found the highest performance when load was near the mean or ~1 SD below the mean. They also found that impairments didn't appear to occur until load increased 1 SD above the mean.

Using Training Load for Reconditioning

Unfortunately, injuries will occur; we can't prevent them. We know that the biggest predictor of injury is previous injury, so we want to make sure when an athlete returns, they're fully prepared and have the least likelihood of re-injury.

Generally, an athlete's training load in their first week back on the ice should be ~50% of what a normal week is for them. From there, increase load gradually and strategically to not spike the acute load (fatigue) too drastically compared to the chronic load (fitness).

In Gabbett's research he found that a large portion (40%) of injuries occur after a rapid increase in load (>10%) from week to week. While he used this information with healthy athletes and their risk of first injury, it's a sound benchmark for reconditioning and avoiding re-injury as well.

Training Smarter and Harder

Not everyone will be in a scenario where expensive GPS and heart rate systems are at their disposal. The good thing is it isn't necessary. Finding a way to quantify load (as simple as session RPE x duration in minutes) is vital to managing your athletes well-being.

Whether you want to have your healthy athletes' performance be at its peak or get your injured athletes back to full participation as quickly and safely as possible (both of which have an influence on team success), no off-ice training method will be as effective as appropriately dosed sport activity.

References

Hägglund M, Waldén M, Magnusson H, et al. Br J Sports Med 2013;47:738–742.

Gabbett TJ. Br J Sports Med 2016;50: 273–280.

Lazarus BH, Stewart AM, White KM, Rowell AE, Esmaeili A, Hopkins WG and Aughey RJ (2017) Proposal of a Global Training Load Measure Predicting Match Performance in an Elite Team Sport. Front. Physiol. 8:930. doi: 10.3389/fphys.2017.00930

About Tim

Tim Lebbossiere is the assistant performance coach with the Boston Bruins (NHL). He holds certifications from FRC, RPR, FMS, and Precision Nutrition. He also has a Master's Degree in Human Performance from Lindenwood University, as well as a Bachelor's Degree in Applied Exercise Science from Springfield College.

You can follow Tim on Instagram (@timlebbossiere) and Twitter (@timlebbossiere).