What led you and the team to pursue this review?
Our biggest reason was finding out the current evidence we have. There are so many potential risk factors in soccer, and with our current interventions to prevent and treat injuries, no one has looked comprehensively at what the basis is behind them.
As scientists, we always have to be very honest. We should always do more studies and try to answer specific questions. With respect to soccer injuries, there’s a lot we don’t know in this space. We are hoping to balance injury interventions with safety, effectiveness and how appropriate they are for the level of competition and resources involved. For example, we probably shouldn’t recommend an expensive recovery program to high school athletes that has limited efficacy data.
What are the types of injuries faced by soccer players?
We see an entire spectrum of injuries in sport. From minor pulls and sprains that require maintenance to some that are devastating, with cardiac arrest happening even in the middle of games with players like the Danish footballer Christian Eriksen. There are also incidents that most sports fans are familiar with, such as cases of torn ACL injuries, which have a huge impact.
Generally, musculoskeletal injuries are very common in soccer. In particular, injuries to the lower extremities account for 80% of all total injuries.
How often are players getting injured playing soccer?
It’s difficult to tell the exact prevalence of these injuries but based on the few professional studies we could find, there are about eight injuries per 1,000 hours of practice or game time.
And another thing we know, as you go up to higher levels of competition in soccer, there are more injuries. So college has fewer than the professional leagues, while high school soccer has fewer injuries than college. Think of it like this: A high school team will practice three times a week, plus a game. But if you are in the academy level, you may practice every day. If you're a 20-year-old playing for Manchester United, you play maybe 12 times a week. It is a totally different exposure, so it can be hard to compare players apples to apples across leagues/levels.
How important is it for sports medicine researchers to understand soccer?
It’s vital. You need to know how it is played, what the rules and tactics are and the mechanics behind how players are taught to do everything from a goal kick to a tackle. You can’t just watch the game as a fan and think you understand everything.
How does sports medicine as a field look at injury prevention?
There are three levels of prevention we use as a field:
- Primary: Trying to prevent injuries before they happen.
- Secondary: Catching an injury early to reduce its effects and impacts.
- Tertiary: Improving the long-term outcomes of a specific injury after it happens.
Taken together, they represent the total scope of approaches we can use, and they vary based on the type of injury. For example, there aren’t many known primary, secondary or tertiary strategies for an Achilles tendon rupture. It’s a rare and brutal injury, but we don’t have evidence for prevention beyond the importance of warm-ups, especially for older players, and a gradual step-up in movement that puts stress on the Achilles.
Compare that to something like a hip abductor injury. There’s a specific exercise players can use called the Copenhagen Adductor Exercise that has demonstrated evidence of reducing hip abductor injuries.
Are there any easy wins in terms of injury prevention players, teams and coaches can make?
I think it's very difficult to answer what lower hanging fruit for injury prevention is. But we’ve made such great strides as a field in two main areas: cardiac arrests and ACL injuries.
Forty years ago, with cardiac arrests, we didn’t even know and couldn’t understand what was happening or what we could have done to prevent it. Now, we’ve seen multiple instances of people acting quickly and saving lives on the field of play.
At the same time with ACL injuries, the organizing body for international soccer – FIFA – realized they were a significant problem. A lot of collaborative work went into a program called FIFA 11+ which is a series of exercises, interventions and pre-habbing to reduce injuries, including ACL injuries. Essentially you are doing rehabilitation before an injury so the area gets stronger.
Artificial playing surfaces often face controversy with increasing injuries versus natural grass – is there any merit to the discussion?
First thing is to note that artificial playing surfaces have changed a lot since their inception. Today’s surfaces aren’t just your astroturf from decades past. Back then, there was increased anecdotal rates of some injuries – MCL, ACL. But today’s surfaces are totally different. I don’t think we have good data either way yet on these new surfaces. Some data actually says artificial surfaces lead to fewer injuries than natural grass. It’s difficult to make a conclusion based on the studies we have so far.
What gaps are there in sports injury research?
Between the men’s and women’s games. If you look at what percentage of the studies have been done on women, there’s a notable shortage. Even in the United States, where women’s soccer has significantly more success than the men’s national team, there are a lack of good studies. We’re hoping to close that gap, but based on current studies, it’s not complete.
It’s also important to understand that the human body is very complex. So when we look at injuries, are certain ones because women have a wider pelvis and different quadriceps angles that lead to different angles when kicking the ball? Are different levels of estrogen and progesterone having an impact? It’s complicated, and we don’t have one clear answer, but we do know that ACL injuries are more common in women in soccer. You have to look at each of these factors.
Combine that with a lack of resources in this space and the need for double-blind controlled studies, which can be rare in this space. Plus, different programs and teams might report their data differently, creating other challenges.
Fortunately, we have some data sets. One actually was created by one of our own epidemiologists, Dawn Comstock from the Colorado School of Public Health, called RIO, Reporting Information Online. And this is a huge data set through high schools, about 100 high schools in the United States. This is an example of a cluster sampling study, and we've been collecting the data for the last two decades.
Would you say it’s a balance between evidence versus potential harm when it comes to injuries and recovery?
Exactly right. I’ll give you an example from my time as a medical director for ultra-marathon races.
At the end of the race, people were taking IV fluid as a routine measure. I asked why and the response was, “Oh, they’re dehydrated.” Of course after an ultra-marathon that makes sense they are dehydrated, but was there any actual scientific evidence that IV fluid is a good solution in those situations? Absolutely not.
There are indications that if you need IV fluid, it’s in a situation where you’re throwing up or severely dehydrated and cannot replace your fluids by drinking alone. It’s not just a little saline; there are potential harms in those situations. My take on it is, we need to know what the potential harms are for an intervention and knowing the mechanisms involved to tell whether it’s going to be harmful to athletes.
