The winter season is well and truly underway thus the busiest time of the year for field sports is upon us. Hand in hand with this comes soft-tissue injuries for the unlucky and unprepared. A significant proportion of these people will experience a hamstring injury (HSI).
HSI’s can be as frustrating as they are common, with one study suggesting they represent 12-16% of injuries in all soccer players. The difficulty, however, arises in the recurrence of HSI with the same study suggesting 22% of those with HSI will have another within 2 months after the initial injury and 25% will re-injure the season after.
These numbers are huge and represent massive failings across a few areas:
- Poor compliance/utilisation of the strength and conditioning during pre-season
- Failed or poor rehabilitation post-injury
- Possibly never doing either of the above!
So, how do these HSI occur in the first place and what is their mechanism?
Peak hamstring force occurs in the late swing phase (Figure 1 – panel 4 and 5, right leg) of the running gait cycle. This force increases as we increase our speed. This is where the majority of HSI occur due to the hamstring having to generate tension whilst lengthening to decelerate the knee.
Plenty of people who have experienced a HSI will tell you they did their warm-up or pre-season work. However, unless you are exposed to loads at high speed and intensity the hamstring will not be prepared. This is due to the hamstring muscles being relatively dormant during the walking or jogging gait cycle. Put simply, going for a jog does not condition your hamstrings enough for field sports. Period.
Knowing this, some canny researchers in Denmark decided to try implementing a hamstring strengthening protocol, known as the Nordic Hamstring Curl (Figure 2) and measure its impact on HSI in soccer players.
This revealed some interesting results.All by implementing a few minutes of extra strengthening exercises to their training sessions. The researchers did include some warnings with the Nordic curl though;
- It should not be implemented prior to a substantial warm-up due to the intensity of the exercise
- Delayed onset muscle soreness (DOMS) was highly prevalent in the first few weeks of this program and should be monitored
I will add a third to this;
- This exercise should not be utilised until a preliminary hamstring strengthening protocol has been implemented
The reason for this is that the exercise mimics the role of the hamstring muscles during sprinting (lengthening whilst contracting) and thus can present a potential mechanism for re-injury if not introduced carefully by a professional.
A more recent paper has found that when combined with a lack of eccentric (lengthening) strength, a short Bicep Femoris long head (BFlh) increased the risk of a HSI. More specifically;
- “For every 0.5cm increase in BFlh fascicle length, the risk of HSI was reduced by 73.9%”
- “For every 10 N increase in eccentric knee flexor strength, the risk of HSI was reduced by 8.9%”
We know from previous research that a really effective way of improving muscle fascicle length is through incorporating eccentric exercises. So through incorporating eccentric exercises, such as the aforementioned Nordic, we are able to significantly reduce our injury risk due to targeting weakness and tightness! This is accurately summarised in Figure 3 (below).
Take home points:
- HSI are common and are usually the result of increasing speed (sprinting)
- They have a high recurrence and thus require proper assessment and rehabilitation in order to curb that trend
- Strength and conditioning is key when trying to reduce injury, especially HSI à do your pre-season!
- The Nordic Hamstring Curl is a great exercise to achieve this, but requires a gradual implementation under the guidance of a professional, and is not for everyone
I hope this brief overview provides some insight into why and how HSI occur and what to do in order to rehabilitate following injury. You can also use this general advice as a way to remain injury free!
If you’ve suffered HSI in the past and are looking to bulletproof yourself for the winter season, contact Roar Physiotherapy in 0421 833 801 to get started on your specific hamstring strengthening protocol today!