Tim Gabbett's guide to acute-chronic load
Written by Simon Austin — January 14, 2019
BRISBANE-BASED Tim Gabbett is one of the most sought-after sports scientists in the world, working with the likes of FC Barcelona, Manchester City and Chelsea. He talked to TGG about his influential work on acute-chronic training ratios.
Tim Gabbett: In the mid-2000s, I became aware of the work of a guy called Dr Andrew Coggan, who was doing a lot of wonderful work in this area. I’m probably standing on his shoulders a fair bit with this stuff. I started using his training-stress balance model to look at monitoring with my players. What I found was that when I was explaining it to them – and to people like strength and conditioning and technical coaches – a lot couldn’t understand the terminology.
So we changed it a little bit, to talk just about the acute to chronic workload ratio. Basically, that’s the size of workload you’ve done in a recent period of time relative to what you’ve done over a longer period of time.
One measure is fatigue, the acute load, and the other is fitness, the chronic load. It allows you to look at workload with both the positives and negatives that come with training.
We know players in general have a sweetspot and a danger zone. You could probably increase your ratio to about 1.3 – that means what you’ve done this week is about 1.3 times greater than what you’ve done in the last four weeks – and you'll be pretty safe.
If you go above that, then you start to put your players at greater risk. It doesn’t mean they will definitely break down, just they’re at greater risk.
1. CHOOSE YOUR TRAINING CYCLE
We’ve used the one week-four week cycle as an example (one week being acute load, four week being chronic load), but it doesn’t have to be that cycle. For some of our teams with congested fixture periods – the Premier League being a good example – we would suggest a different model, changing the acute and chronic loading window.
One week is probably too long for those sports, because you could play three games in nine days. You probably need a shorter acute window to really capture the fatigue, and your chronic loading period probably doesn’t have to be so long. But for an ultra endurance athlete you need a longer chronic loading period because they are working at a much greater percentage of their physical capacity because they have a much smaller room for improvement.
2. THE PARADOX - HIGH LOADS PROTECT AGAINST INJURY
A lot of people tend to think of workload as having a negative effect, but there’s a lot of positive that comes with it. A big part of the ratio is that the pendulum has swung back - no longer do we have to see workload as the bad guy.
Getting the players to high loads is a good thing – it keeps them fit, allows them to perform at a really high level and actually keeps them injury free. High chronic loads being protective is probably the big thing that has been skipped over though. It's the true paradox.
This is not something we’ve found only once - we’ve replicated it in a heap of sports. Part of the problem is that 10 or 15 years ago we were probably analysing our data incorrectly. It was only when we started to build in lag effects that we realised that. Cricket was the first one we found it in, after a six-year study.
When we built our fast bowlers up to really high workloads, as they would experience in a five-day test, their injury risk was close to zero. When we wrapped them in cotton wool, with a four-week average of 30 deliveries in a week, that was when their injury risk was highest. So that was definitely not the answer to creating robust players who could stand up over a five day Test.
We’ve done some analysis for one of the Premier League teams and have some really good data that found similar results. When you build high chronic workloads it actually protects against injuries and sets you up to handle the congested schedules when you have to play two games in a short period of time. When you have spikes in workload – when you ask players to do more high speed running than they’re prepared for, for example – that’s when they're at highest risk of injury.
But at the other end of the spectrum is underloading, when an athlete hasn’t had enough time to develop enough chronic load, which protects you against the spikes. It’s much harder to spike from the ceiling than from the basement.
3. WORK TOGETHER COHESIVELY
The simple approach is to take time to build chronic workload. But the reality can often be different. It might take eight weeks to build chronic workloads, but what if you lose eight games in that time? A manager is always balancing, trying to build high chronic workloads as quickly as possible, but as safely as possible. Often those two things can compete.
The biggest enemy in sport is time. If you have an injured player, you typically don’t have enough time to bring them back to full loads to protect them against injury. As a manager, you have to make tough decisions and you have to win. It’s got to be one of the toughest jobs in the world.
If your player is 75% right, is that enough to get them through a Premier League game? Or might it put them at risk in the next seven days because you’ve spiked their workload?
The experienced managers can calculate cost benefit on the run, but it’s easy to be overwhelmed by those decisions.
I can see it from the medical team’s perspective. They’re under pressure because they’re getting pressure from the manager to get the player back quickly. In the majority of cases you can’t beat biological healing times though. Some injuries, like an ankle strain, you can strap up, but for other soft tissue injuries you just can’t do that. You need to get enough chronic load into the player so they’re safe to go out again.
I can see it from the manager’s point of view too though – he wants to get his team as fit as quickly as possible. He can’t take nine weeks to slowly build up fitness – in his mind he’s thinking 'if I’m going out, I’m going out on my terms'.
There are a lot of different 'players' involved in the process – the player himself, the medical team, the fitness staff, the skill coaches, and so on. Everyone involved in the training process has a role. It’s the teams who can work together that go a long way to achieving that aim.
It could be as simple as the player making sure he maintains minimum chronic load when he goes on his break. If they don’t do anything on say a four-week break then it could take up to 11 weeks to get back where they were before. By maintaining a minimum chronic load they put themselves in a position where they can handle the load that comes during pre-season and are less likely to break down during the season itself.
4. GROUP YOUR PLAYERS - ROBUST, FRAGILE & INBETWEENERS
When I talk about high chronic loads, you don’t necessarily want every player hitting the same load, because this will differ from player to player. Even if we had the exact same load, we would respond differently. It should be individualised. With the way teams are staffed and the resources that go into workload monitoring, it shouldn't be too difficult.
What you end up doing is grouping. The high loaders, the players who can handle load and spikes in load, they’re your robust group. Then you have your inbetweeners, who aren’t robust but aren’t fragile either. Then you have your fragile players. If you asked anyone in your coaching group who their fragile and robust players are, they would be able to identify them. Then you can individualise training programmes among these groups.
And screening through physical tests or muscular-skeletal screening will allow you to identify individual strengths, weaknesses and limitations. You can then develop individual programmes with work-ons – extra work on glutes or calf strength for example.
5. KEEP IT SIMPLE
Thankfully, this has seemed to be a concept a lot of people can get their heads around, which is half the battle with science. We tend to make it more complex instead of simplifying it. I’m a big believer in talking to barmates – if you can’t explain what you do to a barmate then the chances are it’s not that important and you don’t know it well enough to explain.
I just hope this isn't seen as a fad, because that’s something that happens a lot in sport. I really hope load management underpins what we do to try and keep our players injury free. It’s critical.