Injury Reduction (Part 1): It Hurts When I Pull my Hamstring

Hamstring injuries (HSIs) account for 16% of all lower extremity injuries in sport (1). It’s particularly pervasive in high speed running sports like rugby, soccer, ultimate, and track and field.

We know that athletes with a previous lower extremity injury are 2-3 times more likely to re-injure in the following season (2,3). HSIs don’t just affect players though; teams are significantly affected by these injuries with studies demonstrating that there are roughly 5 HSIs per club per season (4).

Today we’ll discuss interventions to decrease the risk of injury and re-injury. In store is a look at Nordic Hamstring curls, the fifa 11+ program, and the importance of psychosocial factors.

Risk factors for HSIs are a good place to start. We’ve found that increased age, decreased eccentric hamstring strength, poor trunk stability, and general fatigue all elevate your risk of injury (4). The strongest predictor of a HSI, however, is a previous HSI, which seems to be a recurring theme in MSK injuries.

The question then becomes, what can we do to modify the risk?

 Figure 1: Adapted from Mendiguchia et al. highlighting the multifactorial nature of HSI (7). Question for later: Is there something missing in this diagram? 

Figure 1: Adapted from Mendiguchia et al. highlighting the multifactorial nature of HSI (7). Question for later: Is there something missing in this diagram? 

Fortunately, there are a number of risk reduction and management strategies at our disposal. One of the best is the Nordic Hamstring (NH) program. This partner-assisted eccentric hamstring exercise isn’t a “magic bullet”, but there is some solid evidence to support its use.

A classic RCT conducted by Petersen and colleagues, assigned amateur and elite-level soccer teams to one of two groups: 1) Control (n=27) and 2) Eccentric Hamstring Program (n=23) (8). The NH group was given a progressive 10-week eccentric hamstring exercise program in mid-season. At one-year follow-up, there were 67 HSIs in the control group (44 new, 23 recurrent) and 15 HSIs in the NH group (12 new and 3 recurrent). Wow.

This shows that the intervention group experienced 60% fewer HSIs! And even more impressive, recurrent HSIs were reduced by 85%! For the nerds out there, there was a number needed to treat (NNT) of 3; which means, that for every 3 high-risk athletes (athletes who have a history of HSI) participating in the NH program, one hamstring injury will be prevented.

 Figure 2: Adapted from the Petersen study. Depicted above is the partner-assisted eccentric hamstring exercise (i.e. Nordic Drops).

Figure 2: Adapted from the Petersen study. Depicted above is the partner-assisted eccentric hamstring exercise (i.e. Nordic Drops).

It seems like a no brainer that elite athletics would be doing this high value, evidence-informed intervention. Right? Problem is… they aren’t. A recent survey showed that only 10% of Champions League and Norwegian Premier League football clubs adhere to any sort of NH program. Disappointingly, 12% of the teams were unfamiliar with NH exercises altogether (9).

So we’ve determined that there’s good evidence and reason to use NH programs to prevent HSI. There’s even evidence to suggest that the age-related risk of HSI can be mitigated with eccentric training (10). An important next question is: could an alternative intervention be just as effective as the NH program?
Aranson and colleagues investigated this very question. Working with a population of elite soccer teams, they looked at two groups:

  1. Warm-up stretching and flexibility training or  
  2. Warm-up and flexibility training plus eccentric strength training (11).

After tracking these soccer teams over two seasons, the addition of the NH program as part of their pre-season and in-season routine significantly reduced the incidence of HSI (11). The stretching group however received little to no benefit on HSI rates, and in fact, had a 50% higher risk for a bad outcome (Relative Risk [RR]=1.53).

For perspective, a RR of 1.0 means you are average, that is, there is no difference in risk between the control and experimental groups. In comparison, the incidence of HSI was lower in teams who used the eccentric training program (RR = 0.43). An RR of 0.5 means the risk is half that of average or a 50% lower risk using the experimental condition (i.e. eccentric hamstring exercise).

With injury reduction and functional performance gains, Nordic Hamstring exercises are a must.

Beyond reducing risk of injury and benefiting hamstring strength, NH programs also lead to improvements in performance indicators like vertical jump height (12) and maximal running speed (13). With injury reduction and functional performance gains, this exercise is a must.

Let’s move on to another protocol for decreasing lower extremity injuries. The FIFA 11+ program, in addition to eccentric hamstring exercises, includes strengthening, motor control, trunk stability, and proprioceptive exercises.

When it comes to effectiveness, there is research that has demonstrated a 68% decrease in lower extremity injury when the protocol is completed at least twice weekly (14). Also noteworthy was the dose-response associated with the program; meaning, the teams who did it more, had an even greater reduction in injury. It’s important to mention that the FIFA 11+ program was not aimed to reduce HSI alone, but all lower extremity injuries.

Despite these excellent tools we have to reduce the risk of injury, I regret to say that the incidence of injury in professional sport is still on the rise. This could be due to compliance issues, but I’d like to raise another factor that is likely at play. In figure 1, I asked, “is there something missing from this diagram?” Well, how about psychological readiness.

Researchers and clinicians are recognizing, more than ever, the influence of psychosocial factors (i.e. stress, anxiety, fear, depression, catastrophizing) on the incidence, prevalence, and prognosis of musculoskeletal conditions. In the case of lower extremity injury, we know that self-reported high life stress is associated with an increased injury risk (15). Day to day life can be stressful; now add all the performance pressures in sport. Will it matter how robust we make the musculoskeletal system if we are not identifying and addressing potential nervous system sensitizers?

What chance do our interventions have if our patients are struggling with fear and anxiety, if they can’t sleep at night and are consumed by stress? Dive into this aspect of patient care. Screen for it with validated measures, and keep your patient’s beliefs, fears, and stress in mind when you’re talking to and educating them. Think about bringing in a sport psychologist, or mental performance consultant to compliment your efforts.

So what is the clinical bottom line?

  1. HSI is common and more likely to occur when there has been a previous injury.  
  2. An exercise program with nordic drops, trunk stability and proprioceptive exercise will help reduce injury risk.
  3. Address the psychosocial features that might be affecting performance.

Want to know more about HSI in sport? click here

Also, visit BJSM Podcasts for many other discussions around the topic of HSI.

References:

  1. Ekstrand J, Hagglund M, Walden M. Injury incidence and injury patterns in professional football: the UEFA injury study. Br J Sports Med. 2011;45:553-558.

  2. Hagglund M, Walden M, Ekstrand J. Previous injury as a risk factor for injury in elite football: a prospective study over two consecutive seasons. Br J Sports Med. 2006;40:767-772.

  3. Petersen J, Thorborg K, Nielsen MB, Holmich P. Acute hamstring injuries in Danish elite football: a 12-month prospective registration study among 374 players. Scand J Med Sci Sports. 2010;20:588-59

  4. Woods, C. Hawkins, R. Maltby, S. Hulse, M. Thomas, H. Hodson, A. The Football Association Medical Research Programme: an audit of injuries in professional football—analysis of hamstring injuries. BJSM. 2004

  5. Gabbe BJ, Finch CF, Bennell KL, Wajswelner H. Risk factors for hamstring injuries in community-level Australian football. Br J Sports Med. 2005.

  6. Gabbe BJ, Bennell KL, Finch CF, Wajswelner H, Orchard JW. Predictors of hamstring injury at the elite level of Australian football. Scand J Med Sci Sports. 2006.                        

  7. Hamstring strain injuries: are we heading in the right direction? Mendiguchia,J. Alentorn-Geli, E., Brughelli M. BJSM. 2012.

  8. Petersen J and Thorborg K. Preventive Effect of Eccentric Training on Acute Hamstring Injuries in Men’s Soccer: A Cluster-Randomized Controlled Trial. American J Sports Med. 2011.

  9. 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. BJSM. 2015

  10. Opar, David A., Williams, Morgan, Timmins, Ryan, Hickey, Jack, Duhig, Steven, & Shield, Anthony (2014) Eccentric hamstring strength and hamstring injury risk in Australian footballers. Medicine & Science in Sports & Exercise, 46.

  11. Arnason A, Andersen TE, Holme I, Engebretsen L, Bahr R. Prevention of hamstring strains in elite soccer: an intervention study. Scand J Med Sci Sports. 2008

  12. Clark, R. Bryant, A. Culgan, JP. Hartley, B. The effects of eccentric hamstring strength training on the dynamic performance and isokinetic strength parameters: a pilot study on the implications for the prevention of hamstring injuries. Physical Therapy in Sport. 2005

  13. Askling, C. Karlsson, J. Thorstensson, A. Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload. Scand J Med Sci Sports. 2003.

  14. Oluwatoyosi B. A. Owoeye, Sunday R. A. Akinbo, Bosede A. Tella, and Olajide A. Efficacy of the FIFA 11+ Warm-Up Programme in Male Youth Football: A Cluster Randomised Controlled Trial. Journal of Sports Science Medicine. 2014.

  15. Steffen, R., Pensgaard, AM., Bahr, R. Self-reported psychological characteristics as risk factors for injuries in female youth football.