Groin Injuries in Hockey Players

Today’s article is an oldie but goodie: this is a guest post I did over on Mike Reinold’s site back in June 2013.  I’ve made a few changes and revisions in this version, since I’ve learned a lot of new stuff and refined some of my opinions since I wrote first wrote it; if you’re interested in seeing the original article on Mike’s site then you can use this link.

 

Groin Injuries in Hockey Players: A Common Problem With a Not-So-Common Solution

 

Being a former competitive hockey player (admittedly not a very good one—”fourth line for life!”) and working predominately with hockey players in a strength and conditioning capacity for the last few years, it has become clear to me that hockey players and groin injuries go together like the artist formerly known as Ron Artest and his psychiatrist. Gold star if you get the reference.

 

Examining the Prevalence of Groin Injuries in Hockey Players

While the relationship between groin injuries and the sport of hockey exists at almost all levels of the game, it has been particularly well-documented in elite players. Several studies have been conducted to assess the prevalence of this specific injury at the professional level. The results have been consistent, and they are troubling.

 

A 1978 study by Sim et al. concluded that “ice hockey players are at high risk for noncontact musculoskeletal injuries because of the excessive force generated during the acceleration and deceleration phases of skating.”

 

A 1997 study by Molsa et al. reported that 43% of muscle strains in elite Finnish hockey players were involving the groin region.

 

A 1999 study by Emery et al. found that “the impact of groin and abdominal strain injury at an elite level of play in hockey is significant and increasing.” According to their data, the rate of groin/abdominal strains in the NHL increased from about 13 injuries per 100 players per year during the 1991-1992 season to almost 20 injuries per 100 players per year during the 1996-1997 season. Furthermore, the recurrence rate was 23.5%, meaning that injuries of this nature went on to plague a significant percentage of players for an extended period of time.

 

More recently, a study by Tyler et al. found that out of 9 NHL players evaluated, all of whom had suffered from groin injuries, four had sustained multiple strains over the course of their careers.

 

The Long and Short of Groin Injuries: Muscular Imbalances in Athletes

With the correlation between hockey players and groin injuries established, it becomes important to understand why this relationship exists. Many people might be quick to attribute it to the violent nature of the sport, but research indicates that this is unfounded. The study by Emery et al. found that upwards of 90% of all groin injuries were actually non-contact in nature.

 

Others might posit that strains are due to the muscles involved being too short and lacking flexibility; sports physicians, physiotherapists, and strength coaches who fall under this category often prescribe stretching of the groin musculature to remedy the issue. The study by Tyler et al., however, found that preseason flexibility of the hip adductors, the primary muscles that make up the groin region, did not differ between NHL players who went on to sustain groin strains and those who did not. This indicates that stretching of the groin is probably not an effective approach toward preventing or treating this type of injury in many cases.

 

What the Tyler et al. study did find was that preseason hip adduction strength of the players who sustained groin injuries was 18% lower than that of the healthy players. They also found that adduction strength was 95% of abduction strength in the uninjured players, compared to only 78% in the injured players. This suggests that a muscular imbalance between the weak adductors and the relatively strong abductors may play a large role in groin issues. The Sim et al. study also supports this view, suggesting that “in ice hockey players, adductor strains may be caused by the eccentric force of the adductors attempting to decelerate the leg during a stride.” The researchers further went on to state that “a strength imbalance between the propulsive muscles and stabilizing muscles has been proposed as a mechanism for adductor muscle strains in athletes.”

 

Detective Work: Delving Deeper to Identify the Cause of the Problem

The logical conclusion then should be that the solution is to strengthen the adductors and stretch the abductors, right? Well, yes, but a more in-depth look at the problem is necessary to determine exactly why this imbalance is present in the first place, that way we can most effectively remedy the issue. As a sports physician, physical therapist, or strength coach, you are not truly solving the problem unless you address the root cause.

 

In order to identify the root cause, it is important to first consider three main concepts. First, it is imperative to understand the biomechanics of skating. This brief excerpt from the study by Sim et al. sums it up very well:

 

“During the powerful skating stride the hip extensors and abductors are the prime movers, while the hip flexors and adductors act to stabilize the hip and decelerate the limb.”

 

The second concept to understand is that these specific movement patterns can have a profound effect on the relative strength—and consequently length—of the muscles involved. Because hockey players, like many athletes, spend so much time in extension, the spinal erectors can become extremely short. The same is true of the hip flexors, which can become short due to the constant forward lean seen in an “athletic stance” as well as the strength required to overcome the aforementioned eccentric force needed to slow down the leg in the recovery phase of a skating stride.

 

Consequently, since the hip flexors pull the pelvis down from the front and the spinal erectors pull the pelvis up from the back, the pelvis can become excessively tilted anteriorly. This lengthens the hamstrings, putting them at a leverage advantage and forcing them to take on more of the load in extending the hips than the glutes. The glutes then would become relatively weak, as would the anterior core. The end result is a player with what Janda called “lower-crossed syndrome”, illustrated in the picture on the right, who could be at risk for both low back and hamstring injuries.

 

Before I continue, it is important to note that the literature on the relationship between specific postures and pain to date shows that specific postures do not necessarily cause pain, although the converse can be true.  As Rob wrote in this article, however, this literature generally has not looked at the athletic population specifically, and I believe that this relationship can be present in people who perform repetitive maximal-intensity movements, like competitive athletes.  I’ve both witnessed and experienced anecdotal success with training methods involving addressing postural and movement dysfunctions in athletes. So while there is a lack of controlled evidence, that does not mean the relationship does not exist in this population.  Anecdotal evidence and expert opinion still constitute evidence, so until I am presented with controlled research suggesting otherwise, I believe that chronic postural adaptations can lead to injury in athletes.

 

Regarding the specific postural adaptation that I previously mentioned–lower-crossed syndrome–the question becomes: how does this play into groin injuries? In order to make that connection, you need to understand the third concept, which is a central tenet of the Postural Restoration Institute (PRI): while muscles are often prime movers in a single plane, they must actually be considered as effectors of movement in all three planes—sagittal, frontal, and transverse.

 

One example of this idea is the hip extensor musculature: while the hip extensors are mostly responsible for movement generated in the sagittal plane, these same muscles—most notably the gluteus maximus—function as external rotators and abductors. This is relevant to hockey because the nature of a skating stride requires players to have strong abductors and external rotators, since they are prime movers in this movement. This overuse can shorten both the external rotators and abductors, and pull the hips into chronic external rotation and abduction (i.e., cause them to become “flared”). Adductor muscles like the adductor magnus, which also contribute to internal rotation, can become passively lengthened and, like the hamstrings in the sagittal plane, be put at an increased risk of injury. This clearly fits the theory of a muscle imbalance as the potential contributor to groin injuries, and it becomes clear from the analysis above that pelvic alignment is important in understanding the root cause of this imbalance. It also makes it apparent that stretching the groin is not only ineffective in many cases; it can potentially feed right into the problem!

Also of note is the postural presentation that PRI refers to as a Left Anterior Internal Chain (AIC), which, due to the anatomy of the human body, is probably the most common presentation that you will come across in both athletes and the general public. Humans are naturally right-side dominant (even if you’re left-handed), due to the fact that we have a heart on the left side of the body, more lobes of lung on the right than the left, a diaphragm that is larger and has more crural attachments on the right side than the left, and a liver that is present on the right but not on the left. In addition to the lateralization of the human brain (research suggests the left hemisphere, which controls the right side of the body, is dominant in motor planning regardless of hand dominance), the net effect is a bias towards the right side, which usually presents as a tendency to shift our weight onto our right leg when standing. The result is a right hip that is

positioned in a state of extension, adduction, and internal rotation, and the left hip will tend to compensate by flexing, abducting, and externally rotating. These adaptations can lengthen the groin musculature on the left side while also somewhat decreasing the chronic length of of the groin musculature on the right side, resulting in the potential tendency for groin issues to be more prevalent on the left side than the right.

 

What’s common in athletes and probably even more common in hockey players, due to the substantial requirement placed on the abductors in the skating stride, is a postural adaptation called the Posterior External Chain (PEC).  In this case, both hips are positioned the way the left hip is in the Left AIC pattern: chronic abduction, flexion, and external rotation.  In this case, the adductors and internal rotators on both sides would be lengthened and placed at risk for pulls or strains.  It should be noted, however, that due to the aforementioned inherent anatomy of the human body, anybody who presents as a PEC also has some degree of an underlying Left AIC pattern.  All of this jargon will become more clear in one of my upcoming articles, which will be an introduction to PRI principles.

 

Shifting Into Neutral: Correcting Pelvic Positioning

This analysis of pelvic alignment and posture brings us to the million-dollar question: how do we fix it? After coming to the understanding that groin issues can be caused by pelvic misalignment in all three planes of movement, you can see why I suggested that strengthening the internal rotators and stretching the external rotators is not a comprehensive solution to the problem. We must address muscular imbalances with the triplanar perspective in order to effectively prevent injuries of this nature.

 

The first plan of attack should be to rectify the imbalances in the sagittal plane. The reason being is twofold: (1) extension limits rotation, and since I already explained that hockey players—and athletes in general—tend to live in chronic lumbar hyperextension and excessive anterior pelvic tilt, it makes sense to resolve that problem first in order to maximize the effectiveness of attempts at repositioning an athlete in the other two planes; (2) specifically regarding the pelvis, if the head of the femur is not appropriately fixed or “seated” (as PRI ninja James Anderson says) in the acetabulum before rotating and/or adducting/abducting, then you’re not getting true rotation at that joint and you’re putting increased stress on the surrounding connective tissue, which could lead to injury. Since properly seating the ball in the socket is primarily accomplished via posterior femoral glide initiated by the hamstrings and glutes in the sagittal plane, it makes sense to address this plane first.

 

Addressing the imbalances in the sagittal plane is fairly straightforward. I like the approach Mike Robertson takes in identifying two “force couples”. The posterior force couple consists of the anterior core and the posterior chain (primarily the glutes and hamstrings), and these two will be weak in athletes living in extension, as I previously mentioned. Hammering the glutes and hamstrings with exercises like Hip Thrusts and Romanian Deadlifts, respectively, will strengthen the posterior chain and tilt the hips posteriorly by pulling them down from the back, the net result being a more neutral alignment since the athlete was in excessive anterior tilt to begin with. With the anterior core, it is important to note that it is the internal obliques, external obliques, and transverse abdominis that are usually weak, as opposed to the rectus abdominis. Strengthening these muscles will tilt the hips posteriorly by pulling them up from the front, also resulting in a more neutral alignment.

 

Barbell Hip Thrust

 

The anterior force couple consists of the spinal erectors and the hip flexors, and these two will be tight. Stretching the hip flexors is crucial; this can be accomplished with stretches like the Half Kneeling Rectus Femoris Stretch. Self-myofascial release can also be useful.

 

Half-Kneeling Rectus Femoris Stretch

 

With the Half Kneeling Rectus Femoris Stretch, it’s important to cue squeezing of the glute on the side of the leg being stretched (Rob’s left glute in the video) to facilitate posterior femoral glide at the hip and prevent the head of the femur from sliding forward and pushing against the anterior ligamentous structures of the hip. Be careful to also not allow the athlete to extend at the lumbar spine, since this reinforces the incorrect movement pattern we are trying to move away from.

 

Stretching the spinal erectors can be accomplished with “prayer position”-type stretches that take the lumbar spine into flexion. Self-myofascial release with a lacrosse ball peanut can also be effective. I like to use exercises that take the lumbar spine into flexion and the pelvis into posterior tilt, thereby inhibiting the paraspinals while concomitantly activating the anterior core.  One example is the wall squat exercise from the Postural Restoration Institute, shown below.

 

PRI Wall Squat w/ Two Arm Reach

 

In this case, we are killing two birds with one stone in strengthening the weak muscles and teaching the athletes to inhibit the tight muscles at the same time. You can also see that in the video there is a foam roller in between my knees—this is to activate the hip internal rotators/adductors, which I will discuss next.

 

Addressing the frontal and transverse planes when it comes to fixing pelvic alignment is the piece of the puzzle that, in my opinion, gets overlooked too often. Again, we want to strengthen the internal rotators and adductors—the muscles might largely overlap but it is important to pattern both movements individually—and stretch the external rotators and abductors. Which of these two planes you target first doesn’t make too much of a difference as long as the sagittal plane comes first, unless the ligamentous structures at the hip have become compromised. If this is the case then the athlete would be what is called “patho-compensatory”, a scenario which requires a number of different considerations that I won’t delve into here.

 

For internal/external rotation, med ball crushes is a good one to strengthen internal rotation (note that this exercise also patterns the adduction movement), and knee-to-knee mobilization is good for both activating the internal rotators and stretching the external rotators. Any exercises that target the semimembranosus (the most medial hamstring muscle) will also help strengthen the internal rotation movement. An easy modification to an already great exercise, which I mentioned earlier, that will help in this regard is having athletes internally rotate the legs during the hip thrust. Considering that it also strengthens the posterior chain, you’re really killing two birds with one stone in repositioning the pelvis with this small tweak.

 

There are also a number of good exercises for patterning and strengthening the adduction movement. Adductor Side Bridges are great in this regard.

 

Adductor Side Bridge

 

The adductor pullback exercise from PRI is another good one.

 

Right Sidelying Left Adductor Respiratory Pullback

 

I generally have athletes perform the adductor pullback exercise only on the left side (so they would be lying on their right side, as Rob is in the video) to address the Left AIC alignment that I mentioned earlier. Doing the opposite by lying on your left side and shifting your right hip forward and externally rotating it (since the right hip tends to be internally rotated) also helps correct this particular alignment. One variation of this latter movement is another PRI exercise called Left Sidelying Resisted Right Glute Max.

 

Left Sidelying Resisted Right Glute Max

 

Conclusion

Simply put, pelvic positioning is an important piece in preventing groin injuries, which affect athletes in all sports, but are especially a problem amongst hockey players. The three main concepts to remember in assessing pelvic positioning in any athlete are 1) understanding the biomechanics of the sport, 2) identifying the effects these movements have on the muscles involved, and 3) considering muscles as contributors to movement in all three planes, even if they are not prime movers in one or more of those planes. These concepts can be applied in order to identify imbalances in an athlete and the effects they have on the position of the pelvis. Once this is accomplished, a program can be designed so that the imbalances can be corrected and the pelvis returned to a more neutral position. After all, neutral is where we want our athletes to be, since that puts them at the lowest risk for injury. And any reputable strength coach, trainer, or physiotherapist knows that keeping athletes healthy is the primary objective of any program. You can’t translate gains in strength and power to the playing field if you’re stuck on the sidelines.

 

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