Hamstring Injuries: A Review of the Recent Literature

I often tell my patients presenting with a hamstring injury, “If you’re going to hurt one thing in your body, you might as well hurt your hamstring”. I often get a bewildered look in return, but the fact is, there is such a large body of research published, and currently being published, on hamstring injuries that we can now treat and manage these injuries much better than ever before.

A major reason for this large body of research is that they are very common in sports that require high speed running and/or kicking, such as soccer and Australian Rules Football (AFL), with 80-85% of all hamstring strains occurring during high speed running [endif]--(1, 2). At the highest professional level, players in these sports get paid (multi) millions of dollars per season. So in order to ensure that highly paid players are not sitting on the sidelines with a hamstring injury, a lot of research has gone into finding out how best to prevent them from occurring, and when they unfortunately do occur, how best treat them so that the injured player can get back on the playing field as soon as possible. ![endif]--

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To give you a rough idea, the average financial cost of a hamstring injury due to “lost time” in European soccer players has been estimated to be around $718K (500,000Euro) (3). In AFL players here in Australia, the average financial cost of a hamstring injury due to “lost time” comes in at a very modest $40K (4). Whichever way you look at it, that’s big bucks per hamstring injury, and it’s no wonder a lot of research has gone into trying to reduce the risk of hamstring injuries from occurring in the first place.

Back in the good old days, if a player went down with a hamstring injury we used to blame it on the player’s older age and/or the player having a past history of hamstring injury. But we can no longer do that. Research has shown that having higher levels of eccentric strength of the hamstrings can mitigate the risk of future hamstring injury in all players, even in older players [endif]--(1, 5). ![endif]--

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Which leads me to the most important point of this paper. The most evidence-based approach - which is a constant among all the papers being published - to reducing hamstring injuries from occurring in the first place and reducing recurrences, is performing eccentric strengthening exercises.

That’s it.

No bells.

Definitely no whistles, or injections.

Just good old fashioned hard-work!

During the 2000’s Scandinavian researchers put a lot of time and effort into hamstring research and made some massive in-roads in reducing the incidence and recurrence of hamstring injuries. There were many studies done, but in one particular study, they discovered that if professional and amateur soccer players did a particular exercise – The Nordic Hamstring Curl – in pre-season training, and then maintained the exercise as part of their training during the competitive season, they were able to reduce new hamstring injuries by up to 60% and recurrent injuries by 86% [endif]--(6). As a result Nordic Hamstring curls were seen as the saviour to all soccer and AFL clubs. ![endif]--

Nordic Hamstring Curl

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Unfortunately, despite many studies showing the significant reduction in risk of sustaining a hamstring injury by performing the Nordic Hamstring Curl, the incidence of hamstring injuries at professional AFL level is not declining, and in fact, the incidence is actually increasing in European soccer players. In a recent paper it was found that over a 13 year period in 36 of Europe’s best soccer teams, the annual incidence of hamstring injuries actually increased by 2% each year (3).

This begs an obvious question; “With all this great research on hamstring prevention, how is it possible that hamstring incidence is still increasing?”. From the literature it looks like there are 2 possible reasons for this, but please be aware that hamstring strains are multi-factorial and these 2 points are certainly not definitive.

The first is the speed of the game. I for one am not privy to the ins-and-out of daily professional football life, but it is widely mentioned in the media that the speed of the game for both AFL and soccer has changed dramatically in the last 5 years. As a result, players are being pushed harder than ever before in training and in competitive matches, and as a result, high-speed running puts the hamstring muscles under a large amount of strain. New research confirms this whereby rapid increases in the volume of high-speed running during games and training relative to what the athlete has been accustomed to over the past 2 playing seasons significantly increases the risk of future hamstring strain (7).

Despite the changing speed and nature of these professional sports, the second possible reason is quite astounding. Research found that during the same time when hamstring injury rates were increasing in European soccer, only 10.7% of the surveyed clubs actually implemented the Nordic Hamstring Curl exercise program to their strength and conditioning program! [endif]--(8). To me this this is unforgiveable. Here we have a evidence-based treatment, and only 10.7% of clubs are adopting it!!![endif]--

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Now on to something that may change the way we rehabilitate hamstrings in the future...

Despite the glowing evidence for Nordic Hamstring Curls, new research has come to light that there may be even a bigger and better exercise for injury prevention and rehabilitation that players should be performing who are involved in sports that have a high incidence of hamstring strains. And that exercise is the 45deg Hip Extension (9).

45 deg Hip Extension (9)

Around 80-88% of hamstring injuries occur in the long head of biceps femoris (LHBF) [endif]--(1, 2, 5), so needless to say it’s advantageous to make this muscle really strong, or selectively target it when it is injured. In this new study, researchers compared the recruitment pattern of the hamstring muscles during 10 typical hamstring exercises used during rehab. Although Nordics have a great evidence-base to reduce overall hamstring injuries, this research found that Nordics do not target the LHBF as well as other exercises. The one exercise that selectively recruited the LHBF the highest, was the 45deg hip extension. However, not to throw the baby out with the bath water, the research showed that the Nordic Hamstring Curl recruited the LHBF the highest out of all the 10 exercises, but it did so with also more activity within the other 2 hamstring muscles, especially the semitendinosus.![endif]--

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So there you have it, a brief run-down of the current trends in hamstring injuries in AFL and soccer and the evidence-base to reduce the risk of injury, and some promising research on how we can rehabilitate hamstring injuries better. Before you all rush out and start doing Nordics and 45 Hip Extensions at training and in the gym, please consult with your physiotherapist, exercise physiologist or strength and conditioning coach prior to doing so. It is vital that programming these exercises into your current training week needs to be carefully considered so that you don’t over-train and increase the risk of hamstring injury or any other soft tissue injury for that mater.

As always please feel free to share this blog with your friends, colleagues, co-workers, team-mates and please get in touch if you have any questions,.

Have a great week!

References

1. Timmins RG, Bourne MN, Shield AJ, Williams MD, Lorenzen C, Opar DA. Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): a prospective cohort study. British journal of sports medicine. 2015 Dec 16. PubMed PMID: 26675089. Epub 2015/12/18. Eng.

2. Bourne MN, Opar DA, Williams MD, Shield AJ. Eccentric Knee Flexor Strength and Risk of Hamstring Injuries in Rugby Union: A Prospective Study. The American journal of sports medicine. 2015 Nov;43(11):2663-70. PubMed PMID: 26337245. Epub 2015/09/05. eng.

3. Ekstrand J, Walden M, Hagglund M. Hamstring injuries have increased by 4% annually in men's professional football, since 2001: a 13-year longitudinal analysis of the UEFA Elite Club injury study. British journal of sports medicine. 2016 Jun;50(12):731-7. PubMed PMID: 26746908. Epub 2016/01/10. eng.

4. Hickey J, Shield AJ, Williams MD, Opar DA. The financial cost of hamstring strain injuries in the Australian Football League. British journal of sports medicine. 2014 Apr;48(8):729-30. PubMed PMID: 24124035. Epub 2013/10/15. eng.

5. Opar DA, Williams MD, Timmins RG, Hickey J, Duhig SJ, Shield AJ. Eccentric hamstring strength and hamstring injury risk in Australian footballers. Medicine and science in sports and exercise. 2015 Apr;47(4):857-65. PubMed PMID: 25137368. Epub 2014/08/20. eng.

6. Petersen J, Thorborg K, Nielsen MB, Budtz-Jorgensen E, Holmich P. Preventive effect of eccentric training on acute hamstring injuries in men's soccer: a cluster-randomized controlled trial. The American journal of sports medicine. 2011 Nov;39(11):2296-303. PubMed PMID: 21825112. Epub 2011/08/10. eng.

7. Duhig S, Shield AJ, Opar D, Gabbett TJ, Ferguson C, Williams M. Effect of high-speed running on hamstring strain injury risk. British journal of sports medicine. 2016 June 10, 2016.

8. Bahr R, Thorborg K, Ekstrand J. Evidence-based hamstring injury prevention is not adopted by the majority of Champions League or Norwegian Premier League football teams: the Nordic Hamstring survey. British journal of sports medicine. 2015 Nov;49(22):1466-71. PubMed PMID: 25995308. Epub 2015/05/23. eng.

9. Bourne MN, Williams MD, Opar DA, Al Najjar A, Kerr GK, Shield AJ. Impact of exercise selection on hamstring muscle activation. British journal of sports medicine. 2016 May 13, 2016.

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