Thank you for coming back and reading the second in my series of blogs relating to the Nordic Hamstring Exercise and its benefits on reduction of Hamstring injury. Hopefully you enjoyed the first blog surrounding the effect of football matchplay related fatigue on the hamstrings ability to produce eccentric torque and also a shift in the angle of peak torque. This second blog will look to delve deeper into the proposed benefits of the NHE and subsequent mitigation of these identified fatigue-related changes.
Eccentric Knee Flexor Strength
The ability to provide an eccentric knee flexor muscle action capable of decelerating the lower leg, that’s what we require from our hamstrings every time we are sprinting through on goal. Or perhaps more commonly, performing a high speed running action to try and get back in position after a misplaced pass!! If we are going to make this sort of mistake then we are most likely to do it under fatigued conditions, which is unfortunately the exact time that our hamstring eccentric strength profile is reaching its lowest (Small et al., 2010).
With this scenario in mind it is important that we provide our players with an exposure to exercises and training that is likely to develop their eccentric knee flexor strength. This is where the Nordic Hamstring Exercise comes in to play!
Alvares et al. (2017) completed a four-week NHE protocol within a small group of physically active adults, with the control group receiving no specific intervention from the study. They found that within the intervention group there was a significant increase in both eccentric torque (13%) and also eccentric “work” (18%) which is explained in this study as an upward shift in the torque-angle curve. These results are particularly interesting as they show positive benefits obtained with only a short, low repetition protocol. These findings are in line with those of Alt et al. (2018) who displayed eccentric strength gains of between 8% and 14% (Figure One) within their four week protocol depending on the velocity of isokinetic assessment.
Figure One: Taken From: Alt et al. (2018).
Both of these studies are useful as they demonstrate the benefits of the NHE on eccentric strength within a short time frame. However neither study looked to see if these benefits carried over into a sport-specific setting of the fatigued athlete. This work was done by Matthews et al. (2017) in a University soccer team. They exposed the players to the 45 minute BEAST protocol of soccer-specific fatigue before repeating the protocol after a four week intervention period. For the purposes of this blog we will look purely at the outcomes of the studies “strength” group who utilised the bodyweight NHE (The assisted NHE is a whole different discussion for a different day, but one that I will definitely be coming to later in the series!!). They displayed that prior to the fatigue protocol being performed at both pre- and post-intervention testing there was no significant difference in eccentric torque at any range of knee flexion (Figure Two). This profile however changes when the post fatigue protocol testing is compared (Figure Three). There is a significantly greater ability to produce eccentric torque at outer range knee flexion ranges when fatigued following the four week intervention. This is important as it would suggest that the NHE is capable of providing the hamstrings with a stimulus that makes them stronger at the key, at risk moments towards the end of each half of football (Woods et al., 2004).
Figure Two: Taken From- Matthews et al. (2017).
Figure Three: Taken From- Matthews et al. (2017).
Hopefully this second blog has provided you with a bit more understanding of the benefits of the NHE in hamstring injury prevention. The next hamstring injury blog will focus on the ability of the NHE to induce fascicle lengthening, and why this is important in reduction of injury risk.
As always I am keen to hear back from people and be challenged on the contents of this blog! Its what makes us better as clinicians!
I will be speaking on this topic @GoPerformUK in Reading on Wednesday evening (14th March 2018), so follow their twitter for more information.
Alt et al. (2018). Velocity-specific and time-dependent adaptations following a standardized Nordic Hamstring Exercise Training.
Alvares et al. (2017). Four weeks of Nordic hamstring exercise reduce muscle injury risk factors in young adults.
Matthews et al. (2017). Strength and endurance training reduces the loss of eccentric hamstring torque observed after soccer specific fatigue.
Small et al. (2010). The effects of multidirectional soccer-specific fatigue on markers of hamstring injury risk.
Woods et al. (2004). The Football Association Medical Research Programme: An Audit of Injuries in Professional Football- Analysis of Hamstring Injuries.