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Injuries

Hamstring Strain Injuries: An Overview (Part 2)

Written by: Stephanie Lazarczuk MSc BSc (Hons) GSR/BASRaT Reg FHEA

Introduction

In Part One I introduced you to some of the current concepts around aetiology and risk factors associated with hamstring strain injury (HSI). In Part Two we will focus on what happens if your athlete does sustain a HSI and consider the programming for both rehabilitation and risk reduction. Depending on your previous education and employment history, some of this information may feel more familiar than other sections. However, I want to reassure you that I don’t have all the answers and our knowledge is constantly evolving. I may well (highly likely) look back at this blog in five or ten years and think how primitive my understanding was. I hope that this will at least give you some food for thought and give you some ideas about what needs to be considered for these athletes.

Assessment

Clinical Assessment

Assessment for a hamstring will follow your typical route of subjective and objective with directed testing. Given the information included in Part One, I hope it is intuitive that the subjective needs to take a dive into the mechanism of injury, past medical history and training history as areas of importance – particularly if you’re not in a team environment and didn’t witness the injury. The objective requires all your usual tests and you can be very specific with strength testing if you have access to appropriate equipment. There are a number of options for tests, with some showing greater prognostic value than others.(1,2) A good starting place might be to browse the Aspetar Hamstring Protocol for guidance. Happily this is freely available with pdf handouts and videos to follow.

When it comes to strength, resisted muscle tests and the Oxford Scale unfortunately won’t really cut it, particularly not at higher levels of play – we need some data. The collection of this might come from handheld dynamometry (or isokinetic dynamometry if you have access), NordBord testing or force platforms. It really does depend on what you have access to, but regardless, you need to ensure you have a consistent testing strategy to make comparisons useful.

Imaging

Discussed in Part One was the link (or potential lack thereof) between location of injury and the severity as identified from medical imaging. Hamstring injuries can be visualised via diagnostic ultrasound or MRI due to their relatively superficial location. The accessibility of these modalities is likely determined by the environment in which you work. However, if there is no access to imaging, good news! There is evidence to suggest it will not offer additional prognostic information beyond that of taking a history and the clinical examination.(1) However, should you consider there to be rationale (e.g. suspicion of rupture which can have serious implications if not recognised), imaging is still worth seeking to ensure you are fully informed.

Exercise Selection

This is going to be a fairly chunky section but given our role as therapists who prescribe exercises, a very necessary one.

Programming considerations

Now…I’m going to start with something that plays on my mind when discussing exercise choices. I have a bit of an issue with the use of the word ‘functional’ in relation to exercises. There are many, MANY different interpretations of this one word, so many that I think it’s lost all meaning. I am firmly of the opinion that your choice of exercise needs to do one of two things, and preferably both.

1. Likely reduces the risk of injury.

2. Improves the athlete’s performance – directly or indirectly, but fundamentally by providing an underpinning physiological adaptation that contributes to performance/execution of skills.

If you are programming an exercise which doesn’t do either of these things, why is it in your programme? I don’t care if you choose a single joint exercise, a multi-joint exercise, a hip-dominant or a knee-dominant exercise, or whether it mimics a sporting movement, as long there is a clear rationale for its inclusion. If it creates a desirable adaptation that can be used by the athlete in some way, surely that’s as ‘functional’ as it needs to be?

In order to know the exercises to include, undoubtedly this requires some physical practice from you. Have a go at them and their modifications. Think about how they feel. If someone says to you “I’m feeling it here, is that right?” how will you know if that’s normal or not without practice? It also requires you to complete a needs analysis for the sport your working in. If you’re part of an MDT, then the more eyes the better as this will give you a wider perspective. Ultimately, by breaking down a skill into its physiological components, this gives you an idea about what adaptations you’re chasing (e.g. force production through either peak force and/or high rates of force development, tendon stiffness and efficient stretch shortening cycles – I’ve randomly picked some here and not necessarily purely hamstring-related, I could go on…). Once you’ve identified the adaptations you are chasing, you identify the stimulus that provides this (e.g. heavy loads, rapid contractions etc.), then you can pick the exercise that delivers the stimulus. Not the other way around. Don’t choose an exercise because you like it, choose it because it will serve a purpose.

As an aside, having a thorough needs analysis also enables you to plan your return to play (RTP) criteria. If you know what your athlete needs to do when they go back to sport, you can tick these off as they are able and you should consider that they might hit some of these milestones along the way, rather than only one big tick of achieving RTP. Back to programming…

How you go about programming across an individual session, a day, a week or a period of months requires some consideration too. This is as much an art as it is a science and takes some practice. The area is too vast to go into great detail here but if you’re less familiar with exercise prescription then again, this might be an area for some self-learning. Investing some time in the vast array of S&C podcasts might be a nice place to start. I will touch on a few areas related to this in the below information but please don’t think this is all your ever need to know or consider.

As I said above, considering the adaptation you want to drive is important, and in relation to injuries we can (should) consider some of the risk factors. It is clearly possible to change muscle shape on a macroscopic scale through hypertrophy training and this may be necessary depending on your athlete, but altering the internal structure of the muscle is also possible. Timmins et al. performed concentric-only and eccentric-only training on an isokinetic dynamometer and determined that eccentric-only contractions led to an increase in muscle fascicles (as a reminder, we discussed the measurement method in the risk factors section of Part One).(3) This has also been found by the same research group when completing the ‘notorious’ Nordic hamstring exercise(4–6) and hip extension exercise.(6)

In studies which included a detraining period, it was demonstrated that changes in muscle architecture induced by eccentric training were lost without a maintenance stimulus.(3–5,7) This should not be surprising as reversal of adaptation was a principle taught even when I was at secondary school. However, by comparison Timmins et al. demonstrated that the concentric-only induced shortening of muscle fascicles did not return to baseline levels after detraining, and as such it is likely necessary to counteract such training with lengthening contractions to maintain initial structure.(3) Clearly, you’re unlikely to program only one contraction mode as your whole programme, so it should be quite simple to mitigate the less desirable shortening. I would also add that I’m not suggesting avoidance of all concentric actions because they are obviously necessary for human movement and sport for power production, for example, nor am I suggesting avoidance of concentric-eccentric exercises.

Strength is obviously a factor which generally requires recovery after most soft tissue injuries, and with all of the studies I’ve cited above, strength increased for all exercise groups. For example, both the eccentric and concentric groups got stronger in the Timmins study.(3) I also cited Presland et al. which examined the effect of high versus low volumes of Nordics.(5) The bottom line was that both high (up to 100 reps per week) and low volume (as few as 8 reps per week) groups got stronger, but there was no difference between the groups in terms of architectural adaptations. Ergo, the suggestion being that after a period of familiarisation (perhaps pre-season conditioning), low volume, high-intensity exercises are likely a sufficient stimulus when performed with quality, time under tension and progressive overload. Useful if you’re time-short in-season. Low volume might, however, not work as well for other exercises which are not maximal/supra-maximal, so you may need to consider programming those differently.

Now I know what you’re thinking. She’s banging on about Nordics, and I am but mostly because I’m talking about available literature but I’ll also refer you back to this earlier statement: “I don’t care if you choose a single joint exercise, a multi-joint exercise, a hip-dominant or a knee-dominant exercise, or whether it mimics a sporting movement, as long there is a clear rationale for its inclusion.” Do I use Nordics? Yes. Do they create favourable adaptations? You betcha. Do they reduce risk of injury? Apparently by up to 50%(8,9) and are likely beneficial for the medial hamstrings as much as biceps fem.(10,11) They’re not for everybody, and I’m not suggesting they should be. In my experience, they’re actually quite well tolerated and while some people will get muscle soreness, you just need to consider when you introduce them and build up, that magic word again, progressively. Equally, there are plenty more options for exercises (Oakley, Jennings and Bishop wrote a nice editorial on this)(12) you just need to think about and manipulate your exercise parameters (reps, sets, load, time under tension etc.) in order to determine your adaptations.

We’ve already discussed exposure to high-speed running as a potential risk factor for injury (Part One), and it is certainly something that needs to be worked into your general programmes. Remember the ‘Goldilocks principle’ discussed and also think about when this fits into your week. If you’re working in a team environment, then you will need to talk to the technical coaches as much as the conditioning staff. If high-speed bouts are already factored into on-field training once or twice a week (or on-track training) then perhaps this is enough of a stimulus. It might be that collectively you decide there hasn’t been enough exposure and players need a ‘top up’. This might change week-to-week. Don’t forget that athletes should have some exposure to high-speed runs during their matches/events so also factor that into your plans.

Treatment/Rehabilitation

Manual therapy

This may prove to be contentious with some, but I view manual therapy as an adjunct treatment for HSI. Tissue turnover is fundamentally going to be driven by mechanical loading and as such, exercise-based protocols are likely to be a superior stimulus for recovery. However, this does not mean that manual therapies cannot be used. I would suggest that they can be employed for symptom modification and sometimes even just from an engagement point of view for the athlete. If it’s an expectation of the athlete and you’re not doing them any direct harm, it may not be so much of an issue (so long as appropriate loading is not sacrificed).

Protocols

Despite the prevalence of HSI, there are still relatively few rehabilitation protocols which have been trialled and have demonstrated their effectiveness. As such, you really need to employ your clinical reasoning in order to structure your protocols. There is some guidance available to you though.

One assessed option is the Askling L Protocol which involves both passive (Extender – supine knee extension in 90° hip flexion) and active lengthening (Diver – concentric-eccentric arabesque/single leg RDL; Glider – eccentric-only, controlled descent from standing towards splits) of the hamstrings and was compared to a ‘conventional’ protocol (cable hip extensions and bridge activities).(13) The L protocol demonstrated a shorter RTP time than the alternative protocol, regardless of whether the initial mechanism of injury was sprint- or stretch-based (although the stretch-type mechanisms still had a longer RTP time than the sprint).

Clearly three exercises which lengthen the hamstrings is unlikely to be enough for a full RTP plan, however they might form part of it. The Mendiguchia algorithm offers greater depth and options with a criteria-based protocol.(14) Given the great depth that is offered, you might want to consider the context if you use this line-by-line. Given the amount of information and tasks to be completed, this algorithm might lend itself to a full-time environment where you have the ability to structure rehab across the day. If you’re in an environment where you have up to an hour, you might find it a bit too much. You might be able to send you patient home to complete some of the tasks, but there are elements which probably need an element of supervision, if only during the initial phases. The bonus of the algorithm is that it includes running-based drills. These drills do, however, tend to be fairly linear in nature.

Additionally, Hickey et al.(15) used a straightforward protocol to compare whether using pain-free or up to 4/10 alters rehab progress. The fundamental message from this is: pain threshold methods progress more quickly, the RTP time isn’t necessarily shorter but if you have longer exposure to useful stimuli that might be important, and there appears to be no increased risk in loading early when comparing the number of injuries during follow up. The protocol also includes a return to run section which increases progressively through intensity and distance. This too, however, is a linear programme so the necessary exposure to cutting movements and the reactivity of being in a team game environment is missing.

As discussed in other sections, the Aspetar Protocol provides both assessment and rehabilitation information. Running drills are also included with both linear and change of direction activities incorporated. You will need to consider how you progress the athlete to ensure they can cope with linear running as well as the progressions to change of direction and ultimately agility.

Late stage rehab

The mid-to-latter stages of rehabilitation will need to progressively return your athlete to their sport. This will include reducing earlier stage options (but not necessarily eliminating them completely) and ensure that all aspects of the sport are included. This circles back to the needs analysis I mentioned earlier. If you know where you’re going, you can make a plan to get there. Realistically this is likely to include explosive actions which have a higher rate of force development, which then progress through stretch shortening activities and include horizontal movements rather than just vertical options (think simple broad jumps or hops and their progression towards scissor runs and bounding). If you remember your basic physics, this is still going to stress the posterior chain/lower limb and at a high level: force = mass x acceleration. If you start moving faster, the force will go up. So, although you might be moving less load, there’s still sufficient stress occurring.

Creating effective acceleration is a great start when running fast but you also need to be able to decelerate effectively to protect other areas – include drills for both. However, unless your athlete only competes in the 100m or only wants to run 20m down the pavement chasing the bus they missed, chances are they need to change direction. As alluded to above, the Aspetar protocol does include some change of direction and makes use of a track which naturally has curves, but just consider the patterns seen in your sport and work from linear to curvilinear runs and then to including sharper change of direction. Agility drills require changes of direction in response to a stimulus and the use of ‘chaos’ also needs to be progressively built to ensure readiness for team sport environments.(16)

This is a very short version of the nature of late stage rehabilitation, so I would urge you to do further learning and also link with professionals who are more accustomed. If you already feel happy with this stage, I would still link with other professionals anyway if only to discuss ideas.

General points

I wanted to add in two final points:

Firstly, you still need to consider your tissue healing timescales. Ultimately, the stages of healing still need to occur and it is possible that this, in part, is why we need on-going maintenance after players RTP. It is unlikely that your player who returns at around three weeks post-strain will have completed remodelling based on conventional wisdom. This topic should underpin your prognosis for all injuries, not just HSI.

Secondly, there is no one-size-fits-all approach to HSI. Research teams and clinicians alike are strong advocates of well-rounded and progressive programmes. This may be contrary to the popular narrative of social media snippets, but you are unlikely to find anyone recommending use of a single exercise as a panacea and for that exercise to be used in isolation. You should consider the role of individual exercises in your programme structure and determine the value that they might add to your end goal.

Summary

In Part One we discovered that the ability to predict HSI is poor but that there are a number of risk factors that we may be able to target. In Part Two there has been some consideration of programming for these. It will be up to you as a clinician to decide on the most appropriate method of trying to target such factors and, equally, the structure of your rehabilitation protocols might be inspired by some of those I’ve mentioned in this blog. Overall, the planning for your athletes whether injured or healthy will be based on your needs analysis and understanding of their sporting demands, and your programming should reflect this. The exercise choices are numerous but you need to determine which adaptations are required and choose an exercise which delivers the appropriate stimulus to create those adaptations. Should an athlete/patient sustain a HSI, a progressive approach is required to restore deficits and ongoing maintenance is needed to continue management beyond return to activity/play, both due to loss of adaptations with detraining and the prolonged risk of reinjury. There are many questions still unanswered regarding the best strategies for dealing with HSI and I’m sure we all look forward to seeing the answers as they emerge.

Steph can be found on Twitter or LinkedIn.


References

1.              Wangensteen A, Almusa E, Boukarroum S, Farooq A, Hamilton B, Whiteley R, et al. MRI does not add value over and above patient history and clinical examination in predicting time to return to sport after acute hamstring injuries: a prospective cohort of 180 male athletes. Br J Sports Med. 2015 Dec;49(24):1579–87.

2.              Whiteley R, van Dyk N, Wangensteen A, Hansen C. Clinical implications from daily physiotherapy examination of 131 acute hamstring injuries and their association with running speed and rehabilitation progression. Br J Sports Med. 2018;52(5):303–10.

3.              Timmins RG, Ruddy JD, Presland J, Maniar N, Shield AJ, Williams MD, et al. Architectural Changes of the Biceps Femoris Long Head after Concentric or Eccentric Training. Med Sci Sports Exerc. 2016;48(3):499–508.

4.              Pollard CW, Opar DA, Williams MD, Bourne MN, Timmins RG. Razor hamstring curl and Nordic hamstring exercise architectural adaptations: Impact of exercise selection and intensity. Scand J Med Sci Sport. 2019;29(5):706–15.

5.              Presland JD, Timmins RG, Bourne MN, Williams MD, Opar DA. The effect of Nordic hamstring exercise training volume on biceps femoris long head architectural adaptation. Scand J Med Sci Sport. 2018;28(7):1775–83.

6.              Bourne MN, Duhig SJ, Timmins RG, Williams MD, Opar DA, Al Najjar A, et al. Impact of the Nordic hamstring and hip extension exercises on hamstring architecture and morphology: Implications for injury prevention. Br J Sports Med. 2017;51(5):469–77.

7.              Presland JD, Opar DA, Williams MD, Hickey JT, Maniar N, Lee Dow C, et al. Hamstring strength and architectural adaptations following inertial flywheel resistance training. J Sci Med Sport [Internet]. 2020; Available from: https://doi.org/10.1016/j.jsams.2020.04.007

8.              van Dyk N, Behan FP, Whiteley R. Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes. Br J Sport Med [Internet]. 2019;(January 1950):bjsports-2018-100045. Available from: https://bjsm.bmj.com/content/early/2019/02/26/bjsports-2018-100045

9.              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(6):1316–23.

10.           Bourne MN, Williams MD, Opar DA, Al Najjar A, Kerr GK, Shield AJ. Impact of exercise selection on hamstring muscle activation. Br J Sports Med [Internet]. 2016;bjsports-2015-095739. Available from: http://bjsm.bmj.com/lookup/doi/10.1136/bjsports-2015-095739

11.           Giakoumis M. To Nordic or not to Nordic ? A different perspective with reason to appreciate Semitendinosus more than ever. Sport Perform Sci Reports [Internet]. 2020;1(15):1–5. Available from: https://sportperfsci.com/to-nordic-or-not-to-nordic-a-different-perspective-with-reason-to-appreciate-semitendinosus-more-than-ever/

12.           Oakley AJ, Jennings J, Bishop CJ. Holistic hamstring health: not just the Nordic hamstring exercise. Br J Sports Med. 2018;52(13):816–7.

13.           Askling C, Tengvar M, Thorstensson A. Acute hamstring injuries in Swedish elite football: a prospective randomised controlled clinical trial comparing two rehabilitation protocols. Br J Sports Med. 2013;47:953–9.

14.           Mendiguchia J, Martinez-Ruiz E, Edouard P, Morin JB, Martinez-Martinez F, Idoate F, et al. A Multifactorial, Criteria-based Progressive Algorithm for Hamstring Injury Treatment. Med Sci Sports Exerc. 2017;49(7):1482–92.

15.           Hickey JT, Timmins RG, Maniar N, Rio E, Hickey PF, Pitcher CA, et al. Pain-free versus pain-threshold rehabilitation following acute hamstring strain injury: A randomized controlled trial. J Orthop Sports Phys Ther. 2020;50(2):91–103.

16.           Taberner M, Allen T, Cohen DD. Progressing rehabilitation after injury: Consider the ‘control-chaos continuum’. Br J Sports Med. 2020;54(2):116–7.

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