This blog aims to provide a critical review of the literature on the topic of injury prevention – what it is, what injury prevention programs are, what the evidence suggests as being effective, and how this should guide the practice of coaches and clinicians.
What is Injury Prevention?
Injuries are a huge topic across sports, occupation, and daily life. Injuries remove people from participating in their desired activities and limit their quality of life. We have strong evidence that participation in physical activity reduces mortality, but at the same time it introduces the chance of injury. Whenever we perform any activity – ranging from walking, picking up objects off the floor, or avoiding a defender to score a goal – we take on an inherent risk of injury. The level of risk and type of injuries that can happen varies by the type and demands of the activity.
With the growing cost of burden of injuries in both sports and occupational settings, we’ve seen a rise in the discussion of injury prevention. There are many approaches taken to try and prevent injuries from occurring – thus arising a host of injury prevention programs. These programs are developed with one aim – prevent people from experiencing injuries.
Injury Prevention vs Injury Risk Reduction
A quick point to clear up here is that injuries cannot be prevented. Instead, what we can do is reduce the risk of an injury from occurring. As we will get into, there are a wide range of risks that are involved in any kind of participation in activity and this means we cannot prevent an injury from occurring – unless we do not participate. In contrast, we can reduce our risk through various formats we will discuss.
For consistency, we will use the term injury prevention program as most of the literature uses this to have a common language.
What are Injury Prevention Programs?
In 1992, a preeminent paper from van Mechelen W, Hiobil H, and Kemper HC was published examining this topic. The authors looked to progress from a random assortment of things thrown together, in an attempt to reduce injuries and take a systematic approach to targeted interventions. In this system, the authors identified a 4 step sequence to do develop an injury prevention program.
- Identify magnitude of the problem
- What is the incidence of injuries
- What is the severity of injuries
- What are the risk factors and injury mechanisms
- Provide intervention to prevent those measures
- Measure the effects and repeat the process starting at step 1.
This system looks to be a phenomenal process at first glance and an effective way to reduce injuries. However, it has a few limitations that are critically impactful to the utility of the programs made through it. As Bahr & Krosshaug 2005 point out, identifying the risk factors and injury mechanism is not so clear cut.
Finding the right risk factors and injury mechanism is a complex task that takes us through a network of uncertainty. To do this, we have to first try and figure out what the risk factors are that matters. These range from internal and external risk factors – such as sex or shoe selection respectively. This is where many people begin to focus in on, pointing blame to certain risk factors such as being female or the type of shoe used. However, just because these risk factors are present does not mean that an injury will happen, nor is it a sufficient means to predict injuries. Instead, it is the summation of the collective risk factors – which are not easy to identify – and the interaction of these with the athlete to determine if it exceeds the capacity of the athlete to lead to an injury to occur in a given situation.
Attempting to have a fully comprehensive review of injury risk factors is difficult, but very valuable. With that in place, we are able to work more proficiently at considering what the injury mechanism is. Traditionally injury mechanisms were identified as a very basic level of biomechanics, primarily looking at the positions of the bones, length of tissues involved, etc. Progressively more factors began to get considered such as the load characteristics of the tissues (such as the anterior cruciate ligament anterior shear tolerance), properties of human tissues involved (such as the force required for a SLAP tear to occur), the neurological effects (such as cognition, fear, coordination) and eventually contextual factors (such as time of play).
With this expansion of perspective we move from description such as:
- An athlete sustained an ACL injury following dynamic knee valgus to
- A basketball player sustained an ACL injury after planting and cutting to maneuver around a defender and she was pushed just as she was passing the opponent with a rapid sideways translation on a high friction surface with a resulting rotation over a firmly planted foot in the third period after having played 17 minutes on the court previously.
Including the playing situation is likely more important than the anatomical situation. Knowing that the injury occurred in more detailed anatomical description than valgus with the foot planted does not necessarily provide much information that has utility to work on reducing further injuries given that valgus is an inherent aspect of the sport. In contrast, in the example provided, we could work on game play situations to reduce likelihood of collision, improved cutting/planting preparation, improved physical capacity for amount of play, shifted time play to other players, etc.
Having an improved understanding of the injury mechanism is beneficial, but in isolation it is still very limited. In order to have a true comprehension of injury risk, we need to understand the relationship between the load (injury mechanism) and load tolerance (athlete’s capacity) which will determine the actual risk. This relationship is influenced by internal risk factors, external risk factors, and the incident event.
With these considerations, we bridge from the prior thought model this comprehensive model:
By reframing this thought process, we can start to consider how a helmet is a means to alter the load and accommodate for greater load tolerance to the athlete.
What does the evidence tell us about injury prevention?
Growing our understanding over time of what leads to sustaining an injury is very beneficial. Without expanding this, we would have less of a conceptual idea on what we can impact to reduce injuries. However, with this growing knowledge on it, have we actually reduced them?
Looking at a large systematic review from Laursen et al. 2014 examining the effectiveness of varying exercise protocols attempting to reduce sports injuries, we can see that there are a few key trends. Physical activity participation is beneficial overall in reducing injuries – reducing just over ⅓ of injuries. However, not all physical activity participation appears to have equal benefits.
Stretching programs do not appear to have any meaningful impact on injury prevention. In contrast, we do see strength training as a whole being beneficial. As well, proprioception and exposure programs demonstrate some level of effectiveness.
Proprioception training programs that focus on neuromuscular control do seem to have a minor impact overall on injury risk. As Hubscer et al 2010 points out, globally the risk reduction for proprioceptive training is not very high, however for ankle sprains it appears to be a very effective intervention.
Strength training is arguably the best overall intervention that shows up across the different studies examining injury reduction. Laurensen et al. 2018 completed a further systematic review and meta-analysis that identified higher qualities studies on this topic and came to this conclusion:
“Increasing strength training volume and intensity were associated with sports injury risk reduction”
This statement is a strong one to summarize the variety of interventions we can use to reduce injury risk. In general, across all of the evidence we see that getting people involved in a resistance training program has more effect than any other intervention at reducing risk of injury. In particular, progressively challenging them over time has the greatest impact.
Does the type of strengthening matter?
Digging into this information further, we can see studies from Leply et al. 2017 and O’Sullivan et al. 2012 identify eccentric exercise to reduce injury risk via beneficial adaptations in various factors such as muscle morphology and motor neuron recruitment.
Eccentric exercise is a component of a motion where the muscle contracts and lengthens at the same time – such as the lowering portion of a bicep curl or when the quadriceps resists the knee bending during a deceleration.
A great deal of injuries occur during an eccentric contraction, so it theoretically makes sense that there would be benefit from doing eccentric exercises progressively based on the literature available for progressive strengthening.
In an upcoming blog we will review various exercises – such as the Nordic hamstring curl – and what the literature has to say on them for different regions of the body.
Are eccentrics the best?
As Bourne et al. 2018 point out when discussing the nordic hamstring exercise, it depends. Different exercises work different muscles differently and we likely need to have a variety of different movements to work the body globally. As well, eccentric motion is a component of a standard exercise for a resistance training program and it is often emphasized when part of a progressive strengthening program – at least periodically.
Does age change it?
One argument that is made at times is that the recommendations for injury risk reduction should change by the population type. This makes sense for changing recommendations for different sports – at least to some degree – but for most other categories, it does not appear to be necessary or beneficial. For example, many people think that programs for those who are very young (youths) or those who are older (seniors) should have a drastically different recommendation than their counterparts in the 18-65 age category. Interestingly, research does not support this belief.
When we examine the literature on youths, we can see a range of studies supporting the benefit for reducing injury risk with a basic resistance training program for youth athletes as pointed out by Faigenbaum & Myer 2009.
- “Most multifaceted conditioning programs that included progressive resistance exercise have proved to be an effective strategy for reducing sports-related injuries in adolescent athletes.”
Shifting to those in older age, there is similar evidence that one of the best ways to reduce the chance of injuries for these people is to participate in a progressive resistance training program. In fact, Joshua et al. 2014 compared a resistance training program to a balance program and found that progressive strengthening had a greater impact on reducing fall risk than balance training!
Is injury prevention just getting stronger?
Reviewing much of the previous information that has been presented, it could be easy to think that it points to just getting stronger to reduce injury risk. If we can take anything away from the work by Bahr & Krosshaug, it’s not quite that simple.
When we look at this topic from an individualistic level, strengthening is likely our best intervention that is not typically done. However, as Coles 2017 points out, there are more factors that can impact injury risk beyond just strengthening.
Factors such as player recruitment, load management, athletic development, and movement efficiency also impact this – though these are not as well researched and not as strongly supported at the current time.
Injuries are bound to happen with any form of participation in a physical act at some point. It is possible that we can impact the risk of them occurring with various types of interventions – most notably progressive resistance training.
It is possible that eccentric exercise may be of particular benefit, but there is still more to learn on that topic.
We see that progressive resistance training is beneficial for reducing injuries for a wide range of athletes, not limited by factors such as age.
A comprehensive injury prevention program will likely be involved in a full training program as other factor such as athletic development may impact injury risk.
In a future blog we are going to explore specific interventions and what the efficacy and effectiveness for these are.
Thanks for reading! Check out our videos on the topic and eaves some questions or comments at the bottom!
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