Growing up playing Gaelic Football, one guarantee is the common sight of players pulling up mid-sprint and falling to the floor. Similarly, the queue of players standing on the sideline during training. So, what can be done to help prevent these lower extremity injuries. Well, as part of my MSc, I am involved with a research group looking at how the hamstrings adapt to various training intervention strategies. This is important, as hamstring injuries are highly prevalent problem amongst many field sports, notably Soccer (Petersen et al. 2011) and AFL (Opar et al. 2014). Similarly, in Gaelic football, hamstring injuries were reported in a 4-year perspective study to be the most common muscular injury, accounting for 24% of all reported injuries and over 50% of muscle injuries (Murphy et al. 2012).
Figure 1. Nordic Hamstring exercise being carried out by one person holding the ankles, as the other person slowly lowers their body to the ground.
One common type of hamstring training that S&C professionals utilise is the Nordic Hamstring exercise. It is very simplistic in its design and can be simply carried out by two people (Figure 1.). This can be included as a supplementary exercise to most S&C programs, and has been shown to be beneficial when performed twice weekly, with repetition ranges varied between 1-13 reps per set (Van der Horst et al. 2015). This can be easily progressed as capability improves by adding more sets, or there are some variations of the movement out there. However, I would suggest becoming proficient at the classical movement before progressing.
****Don’t just let your face smash against the floor****
A high prevalence of Hamstring injuries develop in the late swing phase of the running cycle, mostly during high-intensity sprint components (acceleration (56%), decelerating (15%)). During this time, the Hamstrings are used to eccentrically decelerate the limb as it is undergoing rapid knee extension (Van der Horst et al. 2015). The Hamstrings are a bi-articular muscle (crossing both the hip and knee joints), therefore, in the late swing phase, they are in a lengthened position. This increases negative eccentric work placed on the muscle, leading to the accumulation of micro-damage. The combination of the muscle being in a lengthened position and having to eccentrically control the accelerating limb can compromise muscle integrity. (Chumanov et al. 2007). Therefore, having high eccentric strength to oppose the high internal forces whilst running should be a priority in training programs.
How does the Nordic exercise overcome these issues, especially, with the potential of the high eccentric loading during running contributing to an increased injury risk? Trying to load the hamstrings appropriately is difficult, especially, given the limitations of conventional lower body exercises. The load of a lift is generally determined by the concentric motion, as you have greater eccentric strength (e.g. On a back-squat you can get the load down, but can’t bring it back up). Therefore, this limitation, means conventional Concentric : Eccentric training (Deadlift, Squat etc), doesn’t provide an adequate stimulus for developing the eccentric component of the movement (Reeves et al. 2009). The Nordic exercise overcomes this limitation, by providing a purely eccentric stimulus to the muscle, exponentially loading the muscle as it lengthens.
The introduction of Nordics has been shown in amateur Soccer players to significantly reduce the occurrence of Hamstring injuries (Van der Horst et al. 2015). Similarly, Petersen et al. (2011), reported that 10 weeks of Nordic training interventions reduced injury risk by 60% and reduced the reoccurrence of Hamstring injury by 85%. Therefore, the presence of low inadequate eccentric strength is a modifiable risk factor, that may potentially decrease the risk of future Hamstring injuries (Opar et al. 2014).
So, what adaptations occur in response to the eccentric stimulus, potentially reducing injury susceptibility? The first consideration is the effect on the muscle length, with Nordic training increasing muscle fascicle length (Timmins et al. 2016). One theory is that the change in muscle length was primarily due to the addition of more sarcomeres (functional component of a muscle) in series. This is related to the force-length-velocity characteristics of the muscle, with eccentric Nordic training potentially aiding in the development of more force in a lengthened muscle position. (Blazevich et al. 2006; Timmins et al. 2016). The reason for this exercise induced adaptation is very intricate, involving possible myofiber hypertrophy, resulting from the tearing of the sarcomere Z-disc. Training increases the number of satellite cells and myonuclei. These satellite cells divide and their daughter cells enter the muscle fiber, increasing the rate of protein synthesis, leading to fiber hypertrophy (Petrella et al., 2008)
Written by Emmet McDermott – Masters student in Exercise Physiology at Loughborough University @EmmetMcDermott1
Blazevich, A. J. (2006). Effects of physical training and detraining, immobilisation, growth and aging on human fascicle geometry. Sports Medicine, 36(12), pp.1003-1017.
Murphy, J. C., O’Malley, E., Gissane, C., & Blake, C. (2012). Incidence of injury in Gaelic football: a 4-year prospective study. The American Journal of Sports Medicine, 40(9), pp.2113-2120.
Opar, D. A., Williams, M., Timmins, R., Hickey, J., Duhig, S., & Shield, A. (2014). Eccentric hamstring strength and hamstring injury risk in Australian footballers. Medicine & Science in Sports & Exercise, 46.
Petrella, J. K., Kim, J. S., Mayhew, D. L., Cross, J. M. & Bamman, M. M. (2008). Potent myofiber hypertrophy during resistance training in humans is associated with satellite cell-mediated myonuclear addition: a cluster analysis. Journal of Applied Physiology, 104(6), pp.1736-1742.
Reeves, N. D., Maganaris, C. N., Longo, S., & Narici, M. V. (2009). Differential adaptations to eccentric versus conventional resistance training in older humans. Experimental Physiology, 94(7), pp.825-833.
Petersen, J., Thorborg, K., Nielsen, M. B., Budtz-Jørgensen, E., & Hölmich, P. (2011). Preventive effect of eccentric training on acute hamstring injuries in men’s soccer a cluster-randomized controlled trial. The American Journal of Sports Medicine, 39(11), pp.2296-2303.
Timmins, R., Joshua, R., Joel, P., Maniar, N., Shield, A., Williams, M., & Opar, D. (2016). Architectural changes of the biceps femoris long head after concentric or eccentric training.