Are Nordics all they are cracked up to be? The pros and cons of a popular hamstring exercise
By Damian Raper, APA Titled Sports Physiotherapist and full time Physiotherapist for the Geelong Cats Football club.
Nordic hamstring exercise (NHE), also known has Nordic curls, are a popular exercise used in the prevention and rehabilitation of hamstring strain injuries. Their popularity has been born out of their injury prevention effects in both football (Croiser et al. 2008) and Aussie rules (Orchard et al. 1998) populations. Whilst there is much debate over the risk factors for hamstring strain injuries (HSI), pre-season hamstring weakness has been implicated as a risk factor for in-season HSI for both sports. This implication makes sense from a logical point of view, as the hamstring muscles are required to do a large amount of eccentric work when decelerating the tibia at the terminal swing phase of running (Chumanov et al. 2011). It is at this phase of running that most hamstring injuries are thought to occur (Heiderscheit et al. 2005). Therefore, increasing the capacity of the hamstring muscles to do the task, should decrease injuries, right?
There have been two large randomised-controlled trials exhibiting their benefits. In 942 Danish football players, adding a 10-week NHE program to normal training saw players completing NHE suffer only 3.8 HSI per 100 athlete seasons compared to 13.1 HSI per 100 athlete seasons in the control group (Petersen et al. 2011). Similar benefits were seen in 579 amateur Dutch football players (van der Horst et al. 2015). The intervention group (NHE group) in this study suffered 0.25 HSI per 1000 hours, compared to the control group (no NHE) sustaining 0.8 HSI per 1000 hours. NHE are also known to alter the length-tension relationship of the hamstring (Brughelli et al. 2007) and improve muscle fibre architecture (Timmins et al. 2015). Technicalities aside, if over 750 athletes are able to reduce their HSI risk by a third, then they must be doing something right.
So what is it really that makes NHE so popular? Aside from the weight of positive research indicating their benefits, they are incredibly easy to do. All you need is your own body weight, a partner to hold your ankles and a little bit of determination! A bit of creativity can even see athletes securing their ankles under gym equipment in order to stabilise their feet if they don’t have a partner to do it for them. For practitioners, they have an easy-to-follow, evidence based protocol of sets and repetitions over a 10-week period.
Despite the well-known proven benefits of NHE, HSI still exist. In fact, they are on the rise! A 13-year, longitudinal analysis of HSI in European football has shown that they have increased by 4% annually. Resistance to NHE is often due to athletes and staff being concerned about muscle soreness following maximal eccentric exercise. Muscle damage caused by eccentric exercises is associated with decreased force capabilities and impairment of the excitation-contraction coupling process, thus reducing sporting performance and potentially increasing injury risk. Often the time required to recover from DOMS is unable to be achieved in a busy football schedule. Resistance to NHE is also due their apparent lack of functionality and their ability to predominantly strengthen the medial hamstring muscles over the lateral (and more commonly injured) biceps femoris long head muscle (Bourne et al. 2016). And what if you’re not working with compliant, European footballers? There are other options for preventing hamstring injury. As boring as it sounds, nothing beats a good subjective history! Knowing your athletes and their past injury history is as beneficial as an 8-week strengthening program. After all, the (undisputed) biggest risk factor for HSI is a previous HSI (Freckelton et al. 2013).
HSI are undoubtedly a multi-factorial injury (Mendiguchia et al. 2012). Therefore, they require a multi-factorial approach to injury prevention and rehabilitation. Whilst protocols certainly make life easier and less complicated for physiotherapists, there is minimal homogeneity in HSI – from the mechanism, location and severity to the individual demands of return to sport. Applying an individual injury prevention program or rehabilitation for athletes will be a key focus to the “introduction to assessing and treating hamstring injuries” course. Participants will learn all the key components of hamstring assessment and management, and that may or may not include Nordic hamstring exercises!