Identifying Injury Risks Before the Season Even Starts

Jayson Spikes
September 13 2017 03:29PM

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NHL training camps open across the league this week and the buzz is back in the air! But before rosters can be pared down and preseason games can be played, the players will be put through a battery of tests. And while the off-ice fitness portion of training camp isn't the sexiest, I wanted to discuss its importance.

Now, I have no evidence that NHL trainers and medical staff have read and considered The Association of Hip Strength and Flexibility With the Incidence of Adductor Muscle Strains in Professional Ice Hockey Players, but I'm willing to bet they have seen similar research. This particular article was written in 2001 and provides evidence that absolute and relative preseason adductor muscle strength in NHL players may be helpful in identifying players at an increased risk of adductor strains (or groin injuries).

THE DATA

The authors examined one NHL team across the 1997-98 and 1998-99 seasons, with its players tested in the two preseasons for hip strength and flexibility and then tracked throughout both seasons for injuries.  Of the 81 total players tested in the two preseasons, 34 were cut, traded or demoted to the minors, leaving 47 total, 17 of whom were followed in both seasons.

Researchers started by gathering data on each player’s:

  1. hip flexion strength,

  2. adduction strength,

  3. abduction strength,

  4. adductor flexibility and

  5. hip flexor flexibility.

I'm no doctor, but what I gather from the article and the internet is that:

  • Abductor muscles are those muscles on the outside of the thigh, that are used to open the legs, and

  • Adductor muscles are those on the inside of the thigh used to close the legs.

The exact testing methods for each variable were outlined in a fair bit of detail in the article. While it is interest, I don't think that information is relevant here, but click the link above if you're curious.

There were 141 injuries across the two seasons between the 47 players, 11 of which were adductor strains in 8 players (2 players had strains in both seasons while 1 player had 2 strains in the first season). 3 injuries were to hip flexors, but the sample size was too small to yield meaningful analysis, so no analysis was done on them.

THE RESULTS

On average, preseason hip adduction strength was 18% lower in players who went on to suffer an adductor strain when compared to the group which didn't suffer an injury.

What's more, when comparing relative strength between adductor muscles and abductor muscles, having closer relative strength appeared to offer a material advantage. Players who went uninjured had an average adduction strength that was 95% of abduction strength. In contrast, players who went on to suffer an injury had an average adduction strength that was only 78% of abduction strength. Further, for the injured group, the relative strength imbalance was, on average, more pronounced on the side the injury was suffered (70%) than the uninjured side (86%).

The researchers found that adductor strength of 80% of abductor strength was a useful threshold for predicting injury risks. Of the 94 hips they tested (47 players), 30 of them fell below that 80% threshold while 64 exceeded it. In total, the 30 weaker hips accounted for 8 of the injuries compared to only 1 out of the 64 stronger hips. Thus, based on the population they looked at, the relative risk for an adductor strain was 17:1 when a hip’s adduction strength was less than 80% of its abduction strength.

It's also interesting, at least to my mind, that adductor flexibility was not a statistically relevant indicator of future adductor injuries.

CONCLUSION

One of the reasons for off-ice preseason fitness testing is to identify players at risk of future injuries. The article discussed in this post provides evidence that one potentially fruitful area of testing is hip adductor strength, both in absolute terms and relative to hip abductors.

The authors of the study found that players who subsequently suffered injuries had, on average, hip adduction strengths 18% lower than those players who skated injury free. Further, hip adduction strength was on average 78% of hip abduction strength in those players who were subsequently injured (compared to 95% in those who avoided adductor strains). Hips that had adduction strength of less than 80% of abduction strength had a relative injury risk of 17:1 compared to hips that exceeded that threshold.

While these results are not necessarily earth-shattering, and may, in fact, not surprise you at all, I hope this post sheds some light on some of the things NHL trainers may be looking for in the days leading up to the preseason games.

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Jayson Spikes likes hockey and economics and, since sports economics is totally real a thing, he can write about two of his passions at the same time right here, discussing the behaviour and incentives of fans, players, coaches, general managers and owners. The business, finance and psychology of sports are other topics that interest him and may show up in his posts.
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