Well this is my first venture into the world of blogging, and ahead of my presentation at GoPerform in Reading I will be focusing on the topic of Nordic Hamstring Exercise (NHE). I will start off this series of blogs looking at the reasons why we SHOULD perform the NHE with a review of the literature and discussion of the theory underpinning the principles of the exercise. I will come to the potential arguments against the NHE later in the series.
Fatigue is seen as a key risk factor in not only hamstring injuries, but all non-contact soft tissue injuries (Ekstrand et al., 2011) with acknowledgement of the importance of acute:chronic ratios in elite sport settings (Hulin et al., 2016). That subject though, is a big topic in itself and one for which the sports scientists at the club are much better placed to discuss!! For the purposes of this blog we will look at “fatigue” as what is happening to the muscles of the lower limb during the course of a 90 minute game of football.
Fatigue resulting from match play is acknowledged as a key risk factor to hamstring injury with both Woods et al. (2004) and Hawkins et al. (2001) highlighting the increased risk of injury towards the end of each half (Figure One), and the second half more so than the first half. It appears that following the 15 minute half time the players are subsequently recovered that risk of hamstring injury is decreased. This would be supported by the work of Thompson et al. (2015) who demonstrated a sustained depression of eccentric peak torque values at 0, 7, 15 and 30 minutes (Figure Two) following performance of a fatigue protocol. However it is worth noting that the recovery of peak torque at 7 minutes was very similar to the figures shown at 30 minutes, and therefore we are able to see that there is some benefit to the short half time window in relation to fatigue recovery, even if it is not sufficient to provide full recovery of eccentric torque.
Figure ONE- Taken From- Woods et al. (2004)
Figure Two- Taken From: Thompson et al. (2015)
If we are to affect this fatigue-induced risk we must understand what is occurring from a physiological view point within the hamstring muscles. An initial study by Small et al. (2010) looked to quantify the effects of soccer fatigue on the markers of hamstring injury. They found that at the end of each half the angle of peak torque increased, levels of eccentric torque decreased and finally the functional quadriceps:hamstring ratio shifted in favour of the quadriceps. It is therefore easy to understand why the Biceps Femoris is left vulnerable to injury when attempting to decelerate the lower leg at the end of swing phase. These findings were reinforced by Coratella et al. (2015), although the fatigue protocol was not as realistic to football match play as the SAFT protocol utilised by Small et al. (2010). However the fact that they reported similar findings of peak torque angle shift and decreased eccentric torque values with a resultant alteration in quads:hamstring ratio suggests that they may have still induced sufficient levels of fatigue.
Therefore we just need to find an exercise that can shift peak torque angle closer to knee extension and increase eccentric hamstring torque. The Nordic Hamstring Exercise maybe?! Part Two of my blog series will discuss the potential ability of the NHE to shift peak torque angle of the hamstrings and so address the first fatigue-induced change.
Thank you for taking the time to read this blog, any feedback would be greatly appreciated @PreventionPhys
Coratella et al. (2015). Fatigue affects peak joint torque angle in hamstrings but not in quadriceps
Ekstrand et al. (2011). Epidemiology of Muscle Injuries in Professional Football (Soccer).
Hawkins et al. (2001). The Association Football Medical Research Programme: An Audit of Injuries in Professional Football.
Hulin et al. (2016). The Acute:Chronic Ratio Predicts Injury: High Chronic Workload May Decrease Injury Risk In Elite Rugby League Players.
Small et al. (2010). The Effects of Multidirectional Soccer-Specific Fatigue on Markers of Hamstring Injury Risk.
Thompson et al. (2015). Effects of Age and Muscle Action Type on Acute Strength and Power Recovery Following Fatigue of the Leg Flexors.
Woods et al. (2004). The Football Association Medical Research Programme: An Audit of Injuries in Professional Football- Analysis of Hamstring Injuries.