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THE ARCHITECTURE OF A HAMSTRING STRAIN INJURY

– Written by Fearghal P. Behan, Qatar, Ryan G. Timmins and David A. Opar, Australia and Qatar

 

 

INTRODUCTION

In previous issues of the Aspetar Sports Medicine Journal, risk factors for hamstring strain injury (HSI) have been thoroughly reviewed1,2. These articles identified age, previous injury, strength and perhaps flexibility as the main risk factors for HSI after rigorously reviewing the literature1,2. In recent years large prospective cohort studies have confirmed a significant, albeit weak, association between strength and flexibility as risk factors for HSI, alongside age, body mass and playing position3,4,5. However, more recent research efforts have focused on muscle architecture and its relationship with risk of hamstring injury9,13.

 

MUSCLE ARCHITECTURE AND ‘THE QUADRANT OF DOOM’

Muscle architecture assessment is per-formed using two-dimensional ultrasound to determine the muscle thickness (distance between superficial and deep/ intermediate aponeuroses), fascicle length (a fascicle is a collection of muscle fibres wrapped in connective tissue) and the angle of these fascicles relative to the tendon (pennation angle), within a given muscle (Figure 1). The majority of the research on muscle architecture concentrated on performance parameters of these architectural variables (e.g. relationship of fascicle length and running speed) in a variety of muscles6,7,8. However, an Australian research group completed a series of studies that demonstrated shorter fascicle lengths of the biceps femoris long head (BFlh), the most commonly injured hamstring muscle in high speed running, were associated with an increased risk of HSI8,9. Initially, a retrospective design showed fascicle length of previously injured BFlh was significantly less than the contralateral BFlh8. This same research group, using a prospective study design in 152 Australian soccer players, demonstrated that athletes with shorter BFlh (<10.56 cm) were 4.1 times more likely to sustain a HSI than those with longer fascicle lengths9. Also, athletes with lower eccentric hamstring strength (<337 N) were at 4.4 times greater risk of a subsequent HSI than stronger players9.  If high levels of eccentric knee flexor strength and long BFlh fascicles were present, the likelihood of a future HSI in older athletes or those with a HSI history was reduced9. The presence of short fascicles and lower eccentric strength is now affectionately known as the ‘quadrant of doom’ (Figure 2). These results suggest, albeit indirectly, increasing biceps femoris fascicle length in concert with improvements in eccentric hamstring strength may be an effective strategy for reducing HSI injury risk. 

The mechanism by which shorter fascicles are more prone to injury remains ambiguous. Theoretically, shorter fascicles, with presumably fewer sarcomeres in series, will be more susceptible to damage as a consequence of sarcomere ‘popping’ while lengthening10. It could then be hypothesised that fascicle lengthening may be mediated by the addition of in-series sarcomeres that would reduce excessive lengthening of each sarcomere during eccentric exercise10-13. Fortunately, clear clinical strategies are available to alter fascicle length in hamstring muscles utilising eccentric strengthening.

 

IT WORKS IN THEORY BUT NOT IN PRACTICE?

Repeatedly, eccentric strength training intervention studies have demonstrated an increase in fascicle length of the BFlh14-17, with concentric interventions demonstrating a decrease in fascicle length15,18. These varied interventions include: isokinetic dynamometry15, leg-curls14,18, 45° hip extensions16 and the Nordic Hamstring Exercise (NHE) (Figure 3)16,17. The NHE in particular has received much interest in the HSI literature16,17,19,20, with clear evidence from robustly designed randomised controlled trials of a reduction in HSI19,20. Furthermore, a recent systematic review has further demonstrated the efficacy of the addition of the NHE into HSI prevention programmes, displaying a 51% reduction in HSI risk with the inclusion of this exercise21.

Due to the significant success of the NHE in reducing HSI, it has been described as a hamstring injury ‘vaccine’ and may well be seen by some as the panacea for hamstring injury prevention. If this is the case, surely then HSI rates must be reducing dramatically since all of this level 1 evidence has emerged?  In elite European football (soccer), hamstring injuries rates have not changed (or even slightly increased) between 2001 and 201422. High speed running demands may have increased in elite football during this period which could partly explain the increased injury rates. An apparent contradiction exists between the effective method for reducing hamstring injuries (with evidence from rigorous randomised controlled trials) and reports of increasing hamstring injury rates. In response, a follow-up study of elite football teams was undertaken to investigate their adherence to the evidence-based exercise programmes involving the NHE23. Staggeringly, more than 83% of the clubs were seen as non-compliant with the exercise programme outlined in the randomised control trial by Petersen et al20,23. Of course, a ‘vaccine’ will never be effective if it is not actually taken. Perhaps the exercise dosage has been excessive in previous studies and not feasible for sporting implementation.

Most of the NHE programmes used a progressively increasing high volume prescription: within 5 weeks of commencing the exercise, athletes are asked to complete up to 3 sessions a week, each session comprising of 3 sets of up to 12 repetitions per set20. The lack of adherence in elite football might be in response to the volume of the training programme, therefore, a recent intervention based study compared a high volume to a low volume NHE programme17. The low volume group commenced with two weeks of relatively high volume, where for two days that week they completed four sets of six repetitions of the NHE, similar to the high volume group. Thereafter, the low volume group only completed one session a week of 2 sets of 4 repetitions, while the high volume group increased in volume up to 5 sets of 10 repetitions (Table 1). Surprisingly, both groups had similar increases in eccentric knee flexor strength and BFlh fascicle length, with no statistical differences between the two groups for either variable in response to training17. Although this study did not report prospective injury rates, it is very promising regarding the effectiveness of a dramatically lower volume of NHE on indirect markers of HSI risk.

It would be logical that an athlete already engaging in on-field training, strength training, and competitive matches would be much more likely to adhere to 8 repetitions a week of NHE, rather than over 90 repetitions per week, as per previous protocols20. Investigations on the effectiveness of even lower doses of NHE on these variables has already commenced and soon a minimal effective dose may be established. Hopefully, these lower volume interventions can subsequently be implemented in prospective trials to investigate their effect on HSI levels directly.

 

NOT THE ONLY ONE

Although much of the research discussed involves NHE, this exercise certainly is not the only show in town for improving strength and architectural parameters. This was well demonstrated in a recent trial com-paring the NHE to the 45° hip extension16. The two exercises resulted in similar outcomes for both BFlh fascicle length and eccentric knee flexor strength16. Alongside previous alternative exercise protocols that increased both eccentric strength and BFlh fascicle length14,15,18, these findings illustrate the options and variety available in exercise prescription. It is apparent that eccentric hamstring interventions can be altered, adapted, progressed, and varied depending on the reasoning of skilled practitioners, always with consideration for athlete preference and adherence.

 

CAN WE (RELIABLY) MEASURE ARCHITECTURE OUTCOMES?

If you’re convinced that assessing muscle architecture may be a worthwhile and valuable method to add to your injury prevention and rehabilitation toolkit, you may ask how reliable are the available methods of assessment? Analysing these variables (muscle thickness, fascicle length, pennation angle) utilising ultrasound in BFlh has yielded very positive results. Excellent reliability has been reported at rest and under varying intensities of isometric contraction8. The comparison between mea-suring BFlh with ultrasound and directly through cadavers has also demonstrated robust outcomes24. Although there are clear limitations with measuring a three dimensional structure in two dimensions, certainly it seems to be a reliable, valid and cost effective method for assessing or monitoring muscle architecture6,8,24, particularly with the development of improved methodology25. Technology has inevitably introduced advanced methods for assessing muscle architecture, including diffusion tensor magnetic resonance imaging. These methods have produced fascinating images and demonstrated exceptional results for muscles such as the gastrocnemius and soleus26,27. However, this imaging technique is expensive and requires specialised, time consuming post-processing. We recently investigated whether a simplified diffusion tensor imaging (DTI) analysis method (Figure 4), that could be feasibly implemented clinically, was reliable or sensitive enough to be recommended in musculoskeletal clinical practice for BFlh28. Unfortunately, this simplified version does not compare favourably with ultrasound and does not appear accurate enough to recommend for clinical practice28. Therefore, at present for the assessment of muscle architecture, ultrasound remains a reliable and valid method and certainly the most convenient. With the available expertise, specialist DTI processing is an intriguing area with research currently being undertaken, and it may find its way into clinical practice in the near future.

 

CONCLUSION

Many questions remain regarding the role of muscle architecture in hamstring injuries. Future prospective studies assessing architectural variables would be informative for this area. However, presently muscle architecture appears to be a valuable target to assess and include in injury prevention programmes within sports medicine. The importance of muscle architecture in rehabilitation is also currently being investigated. In the coming years, we might be able to inform clinicians on the effectiveness of various interventions on muscle architecture and hamstring strain injury prevention, rehabilitation and successful return to play. Ultrasounds at the ready….

 

 

Fearghal P. Behan Ph.D.

Research scientist

Aspetar Orthopaedic and Sports Medicine Hospital

Doha, Qatar

 

Ryan G. Timmins Ph.D.

Lecturer in Exercise Science

 

David A. Opar Ph.D.

Senior Lecturer in Exercise Science

 

School of Exercise Science, Australian Catholic University

Melbourne, Australia

 

Contact: Fearghal.Behan@aspetar.com

 

 

References

  1. Bahr R. Preventing hamstring strains: A current review of the literature. Aspetar Sports Medicine Journal 2013; 2:494-499.
  2. Best TM, Tietze D. Risk factors for hamstring injuries: A current review of the literature.  Aspetar Sports Medicine Journal 2013; 2:446-450.
  3. van Dyk N, Bahr R, Whiteley R, Tol JL, Kumar BD, Hamilton B, Farooq A, Witvrouw E. Hamstring and quadriceps isokinetic strength deficits are weak risk factors for hamstring injury: A 4-year cohort study. Am J Sports Med 2016; 44:1789-1795.
  4. van Dyk, Bahr R, Burnett AF, Whiteley R, Bakken A, Mosler A, Farooq A, Witvrouw E. A comprehensive strength testing protocol offers no clinical value in predicting risk of hamstring injury: A prospective cohort study of 413 professional football players. Br J Sports Med 2017; 51:1695-1702.
  5. van Dyk N, Farooq A, Bahr R, Witvrouw E. Hamstring and ankle flexibility deficits are weak risk factors for hamstring injuries in professional soccer players: A prospective cohort of 438 players including 78 injuries. Am J Sports Med 2018; 46: 2203-2210.
  6. Kumagai K, Abe T, Brechue WF, Ryushi T, Takano S, Mizuno. Sprint performance is related to muscle fascicle length in male 100-m sprinters. J Appl Physiol 2000; 88:811-816.
  7. Kwah LK, Pinto RZ, Diong J, Herbert RD. Reliability and validity of ultrasound measurements of muscle fascicle length and pennation in humans: a systematic review. J Appl Physiol 2013; 114:761-769.
  8. Timmins RG, Shield AJ, Williams MD, Lorenzen C, Opar DA. Biceps femoris long head architecture: a reliability and retrospective injury study. Med Sci Sports Exerc 2015; 47:905-913.
  9. 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. Br J Sports Med 2016; 50:1524-1535.
  10. Morgan DL. New insights into the behavior of muscle during active lengthening. Biophys J 1990; 57:209-221.
  11. Lynn R, Morgan DL. Decline running produces more sarcomeres in rat vastus intermedius muscle fibers than does incline running. J Appl Physiol 1994; 77:1439-1444. 
  12. Timmins RG, Shield AJ, Williams MD, Lorenzen C, Opar DA. Architectural adaptations of muscle to training and injury: a narrative review outlining the contributions by fascicle length, pennation angle and muscle thickness. Br J Sports Med 2016; 50:1467-1472.
  13. Bourne MN, Timmins RG, Opar DA, Pizzari T, Ruddy JD, Sims C, Williams MD, Shield AJ. An evidence-based framework for strengthening exercises to prevent hamstring injury. Sports Med 2018; 48:251-267.
  14. Potier TG, Alexander CM, Seynnes OR. Effects of eccentric strength training on biceps femoris muscle architecture and knee joint range of movement. Eur J Appl Physiol 2009; 105:939-944.
  15. Timmins RG, Ruddy JD, Presland J, Maniar N, Shield AJ, Williams MD, Opar DA. Architectural changes of the biceps femoris long head after concentric or eccentric training. Med Sci Sports Exerc 2016; 48:499-508.
  16. Bourne MN, Duhig SJ, Timmins RG, Williams MD, Opar DA, Al Najjar A, Kerr GK, Shield AJ. Impact of the Nordic hamstring and hip extension exercises on hamstring architecture and morphology: implications for injury prevention. Br J Sports Med 2017; 51:469-477.
  17. Presland JD, Timmins RG, Bourne MN, Williams MD, Opar DA. The effect of Nordic hamstring exercise training volume on biceps femoris long head architectural adaptations. Scand J Med Sci Sports 2018; 28:1775-1783.
  18. Duhig D. Hamstring strain injury: effects of high-speed running, kicking and concentric versus eccentric strength training on injury risk and running recovery. Doctoral Thesis. Queensland University of Technology, 2017.
  19. Van Der Horst N, Smits DW, Petersen J, Goedhart EA, Backx FJG. The preventive effect of the Nordic hamstring exercise on hamstring injuries in amateur soccer players: A randomized controlled trial. Am J Sports Med 2015; 43:1316-1323.
  20. 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. Am J Sports Med 2011; 39:2296-2303.
  21. Al Attar WSA, Soomro N, Sinclair PJ, Pappas E, Sanders RH. Effect of injury prevention programs that include the Nordic hamstring exercise on hamstring injury rates in soccer players: a systematic review and meta-analysis. Sports Med 2017; 47:907-991.
  22. 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. Br J Sports Med 2016; 50:731-737.
  23. 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. Br J Sports Med 2015; 49:1466-1471.
  24. Chleboun GS, France AR, Crill MT, Braddock HK, Howell JN. In vivo measurement of fascicle length and pennation angle of the human biceps femoris muscle. Cell Tissues Organs 2001; 169:401-409.
  25. Pimenta R, Blazevich AJ, Freitas SR. Biceps femoris long-head architecture assessed using different sonographic techniques. Med Sci Sports Exerc 2018; 50:2584-2594.
  26. Bolsterlee B, Finni T, D’Souza A, Eguchi J, Clarke EC, Herbert RD. Three-dimensional architecture of the whole human soleus muscle in vivo. PeerJ 2018; 18:6e4610.
  27. Bolsterlee B, Veeger HE, van der helm FC, Gandevia SC, Herbert RD. Comparison of measurements of medial gastrocnemius architectural parameters from ultrasound and diffusion tensor images. J Biomech 2015; 48:1133-1140.
  28. Behan FP, Vermeulen R, Smith T, Arnaiz J, Whiteley R, Timmins RG, Opar DA. Poor agreement between ultrasound and inbuilt diffusion tensor MRI measures of biceps femoris long head fascicle length. Translational Sports Medicine. DOI: 10.1002/tsm2.58.

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Targeted Topic – Hamstring Injuries - Aspetar Experience
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