If, like a lot of my clients, you are an active person and you partake in sports that involve running then the chances are you have experienced a Hamstring injury of some kind at some point. It might be a spasm, a minor strain or a grade 3 tear. Hamstring injuries are pretty devastating for running sports so what can you do to reduce your risk of experiencing one? This blog will set out to look at some of the evidence available regarding stretching and foam rolling and asks whether they are effective. Then we take a look at some of the evidence on strength training and finally, give an evidence-based strategy for reducing your chances of getting a Hamstring injury so that you can get the most out of your sporting activities.
First off let me start with a disclaimer, never self-diagnose injuries and when injury does occur seek treatment from a clinical sports injury specialist, like a registered physio therapist. According to the British Journal of Sports Medicine there are two main types of Hamstring injury associated with soccer players (the kinds of studies seem to be mostly run at soccer academies) and they are; one occurring during high-speed running and mainly involving the biceps femoris long head, the other during movements leading to extensive lengthening of the hamstrings (such as high kicking, sliding tackle, sagittal split) often involving the free proximal tendon of semimembranosus (10). In other words, the large muscle that runs laterally up the back of your thigh can rupture during sprints, while a smaller medial muscle can tear while attempting an overhead kick. So it’s fair to say, for the most part, that the Biceps Femoris is the most likely muscle to get injured while running.
Static stretching is something that sportsmen and women have done for decades, when you do your level 2 and 3 fitness qualifications you get taught to stretch your clients before and after exercise, but does it reduce injury risk?
There is data that shows static stretching, usually a single bout of 30-seconds is effective enough to improve Hamstring flexibility and that static stretching was superior compared with dynamic stretches and muscle energy techniques (7,8) which does makes sense. Although, it’s important to mention that this isn’t so much a case of lengthening the muscles, but improving the stretch tolerance of the muscles and to see those improvements you have to do it multiple times per week over a period of time to experience a small increase in flexibility.
That’s fine, but does improving Hamstring flexibility reduce the risk of injury? It’s difficult to answer this because study design over the years has made it difficult to draw definitive conclusions (9). But the current school of thought is that static stretching alone isn’t effective and, in some cases may contribute to injury risk during sports (6,10). Muscle flexibility isn’t the same as stretching a muscle and some muscles can’t be lengthened. Most of the perceived benefits of stretching, including it’s usefulness as a warm-up, reducing soreness or injury prevention aren’t confirmed by the body of research (13). However, some research (11) does show a benefit to dynamic closed chain stretches for improving Hamstring flexibility and reducing injury risk as part a pre-exercise warm-up. Closed-chain is usually performed on your feet as opposed to laying down. The exercises used here were a single leg hip hinge using bodyweight only and a standing front kick. The kind of thing you see footballers doing during their warm ups on the pitch. Personally, my current belief is that some dynamic mobility is worth including in a warm-up, especially if there is a ballistic or explosive element to your training. While static stretching can feel good post-workout and if something feels good then it can have neuro-emotional effect of some kind, if not a cellular one.
Let’s move on to look at the current bae of personal trainers and sports coaches the world over. The Foam Roller.
A foam roller is a cylinder-like object usually made of compressed foam or plastic. The idea is that you use it to ‘roll out’ your muscles. The official name for this practice is self-myo-fascial release, or SMR. If you have ever used a foam roller you know that it can feel pretty painful and is a good way to master your gurning game and for inventing new swear words. But, here’s a thing, you cannot release fascia without a scalpel so WTF is a foam roller actually doing?
Pre-rolling, meaning to do SMR, prior to exercise has been shown to improve joint range of motion by a small amount. As shown in the graph here, the improvements lasted for some time after rolling, enough time to influence muscle function during exercise (1). Again, is that important? It’s not clear but if you feel like you move more freely that is a sensory feedback that could have some benefits for an athlete.
Some research has looked at handheld massage rollers, rather than the cylinder style rollers that you place on the floor. As you can in this graph an increased range of motion after one set or two sets of 5 or 10 seconds, by a main effect for testing time showed that the use of the roller‐massager resulted in a 4.3% increase in ROM (2). They used the sit and reach test but so what? I mean, the sit and reach test only tests your ability to sit and reach, it has no specific or relevant carry-over to anything in an exercise or sports setting.
Meta analyses have looked at effects on performance due to foam rolling. Looking at the following graphs it is clear there was a net-positive effect from pre-rolling on sprint, jump, strength performances and flexibility. But those positive effects are all quite small and, again, does a slight increase in flexibility really matter for injury prevention? Maybe, maybe not.
The same meta-analysis also showed a net positive effect for post rolling on sprint, jump and strength performance, although again, the outcomes were minor with jump performance in particular being too tiny to really care about. But pain reductions were a bit more significant. So, maybe rolling after a workout could help reduce muscle soreness.
Here’s what the authors concluded (2):
“Although net positives, the results varied greatly in individual studies and positive outcomes were not statistically significant and study limitations and variations in assessment methods make it difficult to confirm. The existing literature thus provides some evidence to support the utilization of FR interventions in sports practice. However, the limited evidence should be considered prior to integrating foam rolling as a warm-up activity and/or a recovery tool.”
A more recent meta-analysis (3) made it no clearer. The evidence is inconclusive but, again, some people do experience a reduction in pain and pre-rolling does show some increase in joint ROM so foam rolling might have some minor benefits in that pain desensitisation might be a placebo that improves mobility and therefore performance. My personal opinion is that foam rollers are a bit overrated and the time spent rubbing yourself over a foam roller could be better sent doing some specific dynamic stability work instead. If you have ever used a foam roller you know that it can feel pretty painful and is a good way to master your gurning game and for inventing new swear words. Although, I do use a trigger point ball on painful areas like the lateral Glutes or IT Band, and although I couldn’t find any evidence that this is anything more than a placebo, I’m inclined to believe that the sensory feedback must be having some kind of intrinsic effect on pain stimuli. Bottom line here, if you like foam rolling keep doing it, but there’s not enough evidence to suggest you need to do it if you don’t already.
If stretching and foam rolling aren’t conclusively effective what is? Well, it makes sense that if you keep injuring a muscle it might just be that the muscle is weak. One area that has been studied in recent years is the effects of eccentric strength. For those of you not familiar with anatomical jargon, an eccentric muscle contraction is the lengthening phase. The primary role of most muscles isn’t, contrary to popular belief, to flex a joint, but to decelerate extension. So, all those young bros swinging the dumbbells up when doing Biceps curls but not controlling the downward phase are missing the best bit.
Back to Hamstrings. One systematic review paper I found looked at the Nordic Ham curl exercise (pictured) to develop Hamstring strength and whether that would reduce rate of hamstring injury (4).
“Findings suggest that eccentric training is effective in primary and secondary prevention of hamstring strains. Study heterogeneity and poor methodological rigor limit the ability to provide clinical recommendations. Further RCTs are needed to support the use of eccentric training protocols in the prevention of hamstring strains.”
While a 2011 paper demonstrated that the Nordic Curl resulted in decreased the rate of overall, new, and recurrent acute hamstring injuries in soccer players (12). The Nordic Hamstring curl is now a staple prescription for Sports Physios and strength & conditioning practitioners who work with athletes.
Meanwhile, post injury rehab is important to reduce the risk of re-injury and eccentric strengthening exercises could well be a good way to keep an athlete off the physio table according to Schmitt et al (5):
“Failing to increase an athlete’s eccentric strength in a lengthened position after a hamstring injury may predispose an athlete to subsequent reinjury. Incorporating lengthened state eccentric training may help reduce the rate of reinjury.”
Recently the British Journal of Sports Medicine released a systematic review and positional stand on injury prevention for soccer players. But these guidelines could be carried over to pretty much any running-based sport. First of all, you need to assess injury risk factors. For example, in contact sports some injuries are unavoidable, it doesn’t matter how many Nordic Ham Curls you do if you get crushed under a pile of 20-stone rugby players while performing the splits. But the following image shows a number of factors that contribute to increased risk of injuries (6).
What I found most interesting about this paper was that their extrapolation of the empirical data and anecdotal evidence based on personal experiences allowed them to come up with a 5-point strategy that encompasses everything that I have been doing with my own clients for a while now. My own practice was similarly informed by empirical evidence and personal anecdote and it’s reassuring to know that much cleverer people than me made similar conclusions. When you work in close proximity to people for a while you start to notice patterns. When assessing clients who had a history of Hamstring injuries I found that they almost always had Glute engagement issues, lacked Hamstring strength and ROM and were generally weaker than they could be throughout their body, largely because endurance athletes like runners tend to only do endurance training. Almost without fail, by strengthening the hips, Hamstrings and core of those clients their Hamstring ROM increased, their injury rate diminished and their performances improved.
Strengthen Hamstrings with an emphasis on eccentric load
This could include exercises like deadlift variations, kettlebell swings and knee flexion exercises like Hamstring Curls – the Nordic Curl mentioned above is a great exercise but it takes a while to build up to that if you are new to strength training. Here’s an example of a deadlift variation that I have used to great effect with many of my running clients:
You would think this one is common sense but people who like exercise often find it hard to not exercise. But it should go without saying that periodizing your workouts and incorporating adequate rest and recovery periods is a no-brainer. Athletes often fail to consider the importance of diet and recovery and then injury can occur if you are not adequately fuelled. This recent blog explains that in more detail: CLICK HERE
If the term ‘lumbopelvic’ doesn’t mean anything to you, it’s your bum. Improve hip stability and power production and your Hamstrings no longer need to hang on for dear life. When it comes to all things Glute related Bret Contreras is the main man and I stole this banded hip complex from him:
In the paper they suggested an emphasis on lower body compound movements such as squats. But, as I alluded to earlier, a generalised approach to strength improvement is important and, therefore, I would advise a basic strength and conditioning program that includes development of strength and power as well as cardiovascular conditioning. I wrote a blog about strength training for endurance sports that fits perfectly here: CLICK HERE
Proprioception is your movement awareness, being mindful of alignment and quality of movement matters and it’s important to develop this sense. This means applying focus and attention to what you do, as you do it and not thinking about what you’re going to have for dinner tonight while you’re attempting a Turkish Getup. Yoga and Pilates help, but because I’m a kettlebell coach and, because we have established that strength is important here I made this video to explain the concept:
I am only a lay researcher at best and this is only a cursory glance at the evidence but hopefully it has given you an insight into how the evidence stacks up. I like how the evidence aligns quite nicely with my own anecdotal experiences and, like with most things in fitness, there are no magic bullets and simply no substitute for good hard work.
In short, stretching your Hamstrings almost certainly won’t prevent you from getting Hamstring injuries. Foam rollers don’t really do much, but if you feel a reduction in pain or soreness that’s a pretty powerful placebo which could have a positive knock-on effect. Strength training is still the king of the mountain so, if you want to reduce your rate of injury or improve your physical performances then get yourself down the gym and start lifting some weights. Or, better still, give me a shout and let’s talk about bespoke training for your specific goals.
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