Training Load and Injury

Injuries. We see a lot. Dealing in the management and prevention of injuries has exposed those of us here at The Injury Clinic to an enormous amount. Every injury is different, because every client is different. Their injuries respond in different ways, recover in different ways and occur in different ways. When looking at athletic injuries, training load is a huge contributor to injury risk. We are finding that increasingly often, load is not appropriately managed. This will increase risk of injury significantly. Appropriate load management is not easy. Regardless of whether you’re managing your own training, or you are under the guidance of a coach, there are a few key things to keep in mind.

*When we speak of ‘athletic injuries’ we are referring to any injury sustained whilst either training for or competing in a sport. It is applicable to athletes of all levels, from recreational to elite.

1. There is a definite association between training load and injury risk, but it’s not a simple one.

Every athletic injury is sustained while athletes are exposed to training and/or competition workloads. There are a number of things to consider when looking that the relationship between load and injury, it’s not just a matter of the progression of weekly mileage.

Important considerations include: intrinsic and extrinsic risk factors, internal and external load, acute: chronic load ratio etc.

It’s not as simple as the higher the load the greater the risk.

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 2. There are multiple risk factors that come together to cause an injury. These risk factors differ for each and every individual who participates in sport and exercise.

When looking at risk factors we can have intrinsic (internal) risk factors that can be either modifiable or non-modifiable; and we can have extrinsic (external) risk factors. See table below.

 
INTRINSIC RISK FACTORS
EXTRINSIC RISK FACTORS
 

 

 

Modifiable

Aerobic Capacity

Strength

Neuromuscular Control

Tissue Resilience

Flexibility/Joint ROM

Technique & Skill Level

Body Composition

 

Environment

Footwear

Protective Equipment

Coaching

Opponent Behaviour

 

 

 

Non-modifiable

Age

Gender

Genotype

Personality

Bony Anatomy

Previous Injury History

Muscle Fibre Type

3. For an injury to occur, there needs to be an inciting event in which biomechanical stress exceeds tissue tolerance.

As we have discussed before, a tissue will become symptomatic when it is stressed beyond its tolerance level. There needs to be an inciting event in which this occurs, however the journey that occurred to reach that point is often full of interplay between risk factors and load.

 

 

4. When looking at the relationship between load an injury, workload is an important consideration, but not the only one.

Workload is essentially the cumulative amount of stress place on an individual from multiple training sessions and games over a period of time. It is inclusive of training and competition intensity, duration and frequency. Workload quantifies the demands imposed on an individual.

Ideally training is prescribed in such a way that the individuals homeostasis is disrupted and optimal adaptation occurs during recovery.

Appropriate prescription of training load is hard! Insufficient workloads fail to induce adaptation or result in detraining; Excessive loads induce maladaptation and over-training.

As with risk factors, we can have external and internal load. External load relates to the amount of work performed (distance covered, balls thrown etc.). Internal load is a measure of the ‘relative physiological and psychological stress imposed’.

A given external load will result in a different internal load responses for every individual. We are all different, so expecting that we will all respond to load in the same way is not realistic. This can often be where generic training programs trip people up. What works for someone else, may not necessarily work for you.

Internal load will be affected by many things, including: sleep, diet, work demands, travel etc. The individual and the demands placed on them outside of training and competition need to be taken into careful consideration.

Individual characteristics such as fitness, training background, personality etc. all come into play.

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5. There are positive and negative responses to training. The positive of adaptation, and the negative of stress and fatigue.

Monitoring workloads to identify stress levels, fatigue, mood and readiness to train are important and should be used to guide alterations to training load.

Training loads are imposed with the goal of maximising performance. Yet whilst training is necessary to induce the ‘reward’ or positive adaptations, it carries its own ‘risk’ of inducing a stress response.

Every time you train, you are exposed to the fatiguing effects of training as well as the potential risks of maladaptation and over-training. It is a fine balance of risk versus reward.

 

6. Workload & Injury Risk. With every training session or competition athletes are exposed to the risk of sustaining an injury.

There is definitely a higher workload = higher risk of injury relationship (Eg. Australian Rules Football Players with a higher total distance and higher sprint distance accumulated over 3-weeks were at greater risk of injury. Higher pitching loads in baseball and higher bowling loads in cricket have also been linked to injury). However, the solution is not to reduced workload to reduce the risk of injury.

In certain situations, reducing load may be appropriate. However, as previously mentioned, adequate workloads are necessary to induce beneficial physiological adaptations such as aerobic capacity, body composition, strength, repeat sprint ability etc.

Many of these adaptations are not only required for improving performance, but also for reducing injury risk. So, workloads that are too low may not only decrease performance, but may result in lower levels of fitness and resilience, ultimately increasing risk of injury.

Whilst “total” workload is an important consideration, it is the rate of change in load that appears to be a stronger predictor of injury.

 

7. Acute: Chronic Ratio.

We have spoken of this previously, but for a quick re-cap…acute (1-week) and chronic (4-week) load relationship is exactly that. The ratio of acute on chronic load. High acute: chronic ratios result in “spikes” in load that have a strong association with injury risk. This has been shown in cricket, rugby league, soccer and subsequent injury during return to play.

E.g. When looking at the sport of Cricket, studies have shown that acute: chronic ratios of > 1.5 increased injury risk by 2-4 times in the following 7 days.

So, if high workloads are associated with a greater injury risk, but also required for beneficial adaptations, improvement and injury prevention, how do we determine what is appropriate and “safe”?

We look to the acute: chronic ratio. High chronic workloads have a potential preventative effect as long as week-week load changes are kept within approximately 10% and the acute: chronic load ratio is kept in a moderate range, so essentially no training spikes.

If has been found that athletes with high chronic workloads and a high acute: chronic ratio are at the greatest risk of injury.

However, if acute: chronic load ratios are kept with what is considered to be a “moderate” zone, those with a high chronic workload have one of the lowest risks of injury.

Workloads should be high enough to produce beneficial adaptations, however these beneficial effects can be negated if athletes are exposed to load “spikes”. It is these “spikes” that are likely responsible for a large proportion of non-contact soft tissue injuries.

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SUMMARY

Optimal load management entails the accumulation of high chronic loads, while minimising spikes by maintaining week-week changes within approximately 10%.

Overuse injuries or injuries associated with training load errors may be strongly related to load, but they still have an inciting event of cumulative tissue overload, even if a specific event cannot be identified.

Every athlete, from recreational to elite, needs to be considered as an individual with different internal load responses. Internal load is just as important to monitor and guide training as external load.

 

  • High workloads increase exposure, thereby increasing injury risk

 

  • Workloads that induce high levels of negative changes to modifiable internal risk factors and internal load responses increase injury risk

 

  • Workloads that maximise positive adaptations while minimising fatiguing effects will help improve resilience and risk of injury

 

REFERENCE

Windt J, Gabbett TJ. How do training and competition workloads relate to injury? The workload—injury aetiology model. Br J Sports Med. 2017;51:428–435.

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