Given that overuse injuries are the most common form of injury amongst endurance athletes, individuals often question how to know if they’re overtraining. Such a simple question is often met with subjective responses, as individual circumstances make it so that there is no easy equation to recognize overtraining. Take a runner who has recently increased their running to 50km weeks, causing them an injury compared to an Olympic Ultra marathoner who regularly does 150km weeks without a problem. So is there such thing as overtraining, or is it only inappropriate training loads relative to individual athletes that causes injury?

Training workload and injury

Your training workload refers to the combination of how MUCH, how OFTEN and how INTENSE your training is. Sedentary people have a training workload of 0, but us endurance athletes may have training workloads of 2000-6000 per week (More to be explained in a moment)

The reality is, and sometimes us coaches don’t want to admit this, there is a positive relationship between training loads and overuse injuries (13). However, it’s not as simple as black or white.

There is substantial evidence that training also has a protective effect against injury. Consistent higher training workloads will improve performance (1) while reducing subsequent injury risk, due to the physical preparedness and better well-developed physical qualities associated with training (2, 3, 4, 5 , 6, 7).

On the other end, undertraining amongst endurance athletes is also associated with overuse injuries. This may be due to inconsistent loading from week to week, or a spike in workload on competition day or spontaneous sessions, both impairing the body’s ability to adapt and tolerate these training loads (8, 9, 10)

With this in mind, there is an optimal level of training load for athletes to achieve high level of performance with minimal injury risk. Too little or too much training becomes sub-optimal for overall athletic performance. See the U-shaped graph redrawn from Orchard (11) below:

Graph from Gabbett, T (2016)

External vs internal training load

Runners often think of workload as the total weekly distances run. However, workload is anything that contributes to fatigue to the physical body.  It is a seesaw act between external and internal loads. External loads include all the factors of a training program affecting the body. Internal loads are the individual factors which make up an athlete, determining their ability to tolerate the external loads.

External loads:

Training frequency
Training duration
Running distance
Running speeds
Running terrain
Weights in the gym
Exercise selection
Reps and sets

Internal loads:

Training history/experience
Injury history
Psychological state
Sleep quality/quantity

The idea of training for performance is that external training loads should be challenging enough to stimulate the body to adapt, but doesn’t exceed the internal loads by too much at any time or over a prolonged period of time.

Be aware of all the different factors of external loading, especially running speeds and terrain (Eg Adding in more speed work or hilly, trail runs) which may not increase the overall distances run, but can contribute to excess external loads that can cause overuse injuries.

Knowing your training workload

So how do you know if you’re training too little or too much? Let’s do this through 3 simple steps:

  1. Calculate your workload on a weekly basis
  2. Determine the weekly rate of change
  3. Determine the acute:chronic workload ratio
  1. Calculate your workload

This can be done using the equation: RPE x duration

RPE is the Rate of Perceived exertion- A scale between 1-10 of how you personally perceived that training session to be.

Duration represents the total number of minutes spent in training.

Using this equation, the workload for a hard, threshold 40 minute run will be: 7 (Hard RPE) x40 (Training duration in minutes) = 280

The workload for an easy 40 minute run will be: 4 (Easy RPE) x 40 (Training duration in minutes) = 160

Add up the workload for each session of your week, and that will give you your total workload for that week. Majority of weekly workloads will fall anywhere between 1500-6000. Off-season training may be at the lower end of this weekly totally, competition time may be towards the higher end of the weekly total.

2. Determine the weekly rate of change

As you calculate your workload each week, you will be able to see the changes in week to week as a percentage.

An increase from 2000 to 2200 is a textbook 10% increase.

An increase from 2000 to 4000 is a 200% increase.

The rate of change in workload is important to look at it is one of the most significant factors associated with overuse injury. Research shows that when training loads are fairly constant week to week (<10% increase in load), then the risk of injury is less than 10%. However, when training load increases by more than 15%, the injury risk can be elevated up to between 21-49% (12).

However, there are exceptions to the rule. Consider these two separate athletes:

  • Athlete A is a seasoned marathoner who has been running 100km weeks consistently for the last 6 months, and goes on a one week holiday to Bali without any running during this time.
  • Athlete B is also a seasoned marathoner who is used to 100km weeks over many years, but the last 4 months have been injury-stricken, with no running at all due to a stress fracture.

According to the week to week rate of change model, both should start at 1km total weekly distance in their first week back at training (already technically a 200% increase from 0km). The from there, they are only allowed to build up 100m each week for a long, long time (10% increase each week). But I think it is clear that athlete A can return to 100km within 1-2 weeks upon return from his holiday relatively safely (Although it’s technically a 1000% increase from his 0km week in Bali), but athlete B may initially need a more conservative approach, with rate of change less or equal to 10%.

These scenarios bring to light the need for a more comprehensive system to track change of rate of workload. Bring in the acute:chronic workload ratio.

  • Calculate your acute:chronic workload ratio

The acute:chronic workload ratio is very similar to the above week-to-week rate of change model, but takes into account not just one week at a time, but a chronic timeframe (usually approx 4 weeks), and an acute timeframe (Current week). The chronic timeframe indicates fitness and individual capacity levels, while the acute timeframe indicates the current workload and fatigue.

Graph from Gabbett, T (2016)

If the chronic load is low (Suggesting that the athlete has not developed adequate fitness and not well-prepared), but the acute load is high (High fatigue), then the acute:chronic workload ratio will exceed 1, and put the athlete at high risk of injury.

Conversely, if the chronic load is high (Suggesting that the athlete has developed adequate fitness and is well-prepared), and the acute load is lower (Minimal fatigue), then the acute:chronic workload ratio will be around 1 or less, meaning the athlete is well-prepared and in a good place.

So whether you’re in the middle of off-season, preparing for an event, returning from a holiday, returning from injury, using the acute:chronic workload ratio will help you to check whether you’re increasing your weights or km’s at an ideal rate, and ensure you’re optimally progressing your training.

So what now?

As a coach, I am constantly writing programs with consideration of the acute:chronic workload, and many other variables such as psychological state, sleep, nutrition, goals just to name a few. All of these factors form the science of coaching to ensure that the client is able to maximise their chance of success and minimise the chance of injury.

For you, you now know how to calculate where your training is at currently compared to the last 4 weeks. Especially if you’ve had an injury, you may be able to track back to see where your training loads spiked before the injury occurred. This is currently one of the most accurate and best accepted methods to track training load, and will allow you to monitor your workloads into the future. All the best, and happy maths!

Ultimately, the best programming for you depends on many variables that cannot be fully explained in one blog post. If you would take your athletic development to the next level, book in for a complimentary Initial Assessment with Trang by emailing [email protected].


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