Hamstring strains are an annoying part of life that a lot of sports people will have at some point throughout their time playing competitive or recreational sports. They are the most common muscular injury in AFL, soccer, American football and Track & field, and account for a large amount of time spent on the side-lines. Because of this there has been a lot of research into ways to reduce the risk of hamstring strain injuries from occurring in the first place. To understand how to reduce the risk, we first need to understand the risk factors.
Some of the major risk factors will make a lot of sense;
- previous hamstring injury
- poor strength in the hamstrings
- sporting moments where there is large load through a hamstring that is already on stretch (ie heel strike of the foot in a full sprint or landing from a jump with a relatively straight knee and bent hip).
Some of the other risk factors may not make a lot of sense without explanation, these being;
- Imbalance in muscular strength from leg to leg of >20% puts you at 3.4x the risk of having a hamstring strain within the next season.
- Having short biceps femoris fascicle length puts you at a 4x increased risk.
To understand what this means, you need a little bit of background information about the anatomy of the hamstrings and the architecture of a muscle. The Hamstrings are a group of three muscles in the back of your leg which are called your semimembranosis & semitendinosis (the two towards the middle of your leg), and the biceps femoris (outer one). A muscle is made up of a whole heap of different layers of fibres, that are arranged like the picture below. The fascicle is the functional bundle of individual fibres that all contract together, and to gain the most power out of our muscles the fascicles all need to contract together. Now as I said above, having a short fascicle length is something that has been proven to put you at an increased risk of hamstring injuries, and luckily enough the researchers have found ways that we can address this change and thus reduce our risk.
The overall mantra of avoiding hamstring strain injuries and creating sports proof hamstring muscles is LONG & STRONG. This means equally strong muscles in each leg, and long fascicles in our muscles. With this mantra in mind, we can address the majority of the risk factors for having a hamstring strain in the first place.
STRONG – as you see in the risk factors above, poor strength & strength asymmetry from side to side are two big modifiable risk factors for hamstring injuries. So obviously then we need to be doing hamstring strength training to reduce our risk. The less obvious thing then is what type of strengthening. Research has shown that by doing concentric hamstring training (muscle shortening while it contracts) we are definitely able to increase our peak force output from the hamstring muscles (strength) however this has also been shown to reduce the length of our biceps femoris fascicles, which is working against our LONG & STRONG mantra.
LONG – our fascicle length is actually something that we are able to change. The way that we do this is via repeated eccentric muscle contractions (contracting and lengthening at the same time). Research has shown that we are able to lengthen our fascicles with loaded eccentric exercise, and luckily enough for us this is also addressing the strength part of our mantra. The only catch here is that positive changes in fascicle length can be made in a four-week eccentric training program, but with a further four weeks deload, where we don’t continue with our eccentric strength training our fascicle length is back to where it started. The frequency of eccentric training needs to be at least weekly to maintain the changes in fascicle length.
So, the obvious question now is – HOW DO I DO IT?
There are plenty of different eccentric focused hamstring exercises that are at different levels of difficulty. Some of these include;
- Glute bridge hamstring sliders
- Stiff leg deadlifts/ Romanian deadlifts
- Single leg Romanian deadlifts
- Nordic Hamstring curls (very difficult)
The exact exercises used doesn’t seem to play a big factor in the outcomes of the training, as long as the individual is putting a load through their hamstrings that is close to their upper limit of muscular capacity. This means that someone weaker can achieve similar results from including glute bridge hamstring sliders as someone stronger can achieve from including Nordic Hamstring curls. As long as you are working on moving towards more load in the exercises, you are doing your best to reduce risk of hamstring strains.
MAJOR TAKE HOME MESSAGES
- Remember the mantra LONG & STRONG
- Train your hamstrings eccentrically to address risk factors
- Continue to eccentrically train your hamstrings once per week to maintain the changes in muscle architecture.
Good luck with building those sports proof hamstrings!