Nordic Hamstring Exercise and Associated Muscle Architecture Changes

There’s an ungodly amount of data and published research that shows hamstring strains are among the top injuries in sport. Reviews cover that introduction over and over so I’ll save you the few minutes of reading another intro and skip over to the meat of this blog. If you do want to get a quick intro to injury rates, mechanism, and risk factors, click HERE.

When we take a look at what training methods and exercises are being used to develop the hamstrings, typically research looks at the Nordic Hamstring Exercise (NHE). Much of the current research that I have seen is using the NHE to determine if the exercise can have an effect on eccentric strength, pennation angle, fascicle length. All three have can have an impact on performance and reducing the risk of injury.

In regards to eccentric strength, the research has come to a hard conclusion that NHE promotes eccentric strength. Even if we forget about the next two points, pennation angle and fascicle length, eccentric strength alone as a mechanism of protection should be enough reason to use the nordics for developing the hamstrings.

Pennation angle of the muscle fiber is the angle at which the muscle fibers run in relation to the muscle itself. The advantage of pennate muscle fibers in relation to parallel fibers is the increased amount of force production assuming constant muscle mass. (Ethier & Simmons, 2007) With this idea in mind, the more acute the pennation angle, the more force that is capable of being produced. Although, it does appear more research needs to be done here to fully understand this topic due to changes in cross-sectional area being a factor.

A third potential benefit of the eccentric development of the hamstring is the fascicle length. Muscle fibers are bunched together in what is called a fascicle. The fascicle length is determined by the number of sarcomeres in series. It has been shown that fascicle lengths increase as a result of resistance training and especially eccentric loading. (Ema et. al., 2016) This is an important factor to consider because as fascicle length the increases, the muscle has the ability to shorten to a greater extent and with more velocity than the same muscle with a shorter fascicle length.

Two recent publications on the NHE had these findings:

  • In one nordic hamstring exercise study (Fernandez et. al., 2017), the group went through 8 weeks of the nordic hamstring exercise exposure. After 8 weeks, muscle fascicle length increased, and muscle pennation decreased (both good things). But, guess what happened after the 4 weeks of detraining? Both fascicle length and pennation angle started to return to their pre-training state. This shows evidence for the continuation of eccentric hamstring development in the in-season which is sometimes, unfortunately, shied away from.
  • In another, relatively short nordic study (Alvares et. al., 2017), the 4 week (8 session) study found that eccentric strength of the biceps femoris increased, the pennation angle decreased, and the fascicle length increased. This shows that not only is the nordic hamstring exercise a great option to keep the hamstrings long and strong, but also that it can create those muscle architecture changes in a very short period of time. In other words, even if you’re late to the game in terms of hamstring development, it doesn’t take very long to see positive changes.

It is ideal to introduce eccentric hamstring training in the off-season or pre-season to have the time to develop the qualities outlined above. If you’re in the off-season it’s typically fine to first introduce them with no major concern with the athlete being sore. Any novel stimulus will most likely make an athlete sore. In the pre-season and in-season, though, a more modest approach with simple progressions may be needed.

During the in-season there a couple ways to introduce eccentric hamstring development. We can introduce in the NHE low very volumes (i.e. 1×6, 2×4) and slowly work our way up over the course of a couple weeks or we can regress the exercise to double leg or single leg hamstring/glute bridges in similar volume prescription to what traditional NHE would be (i.e. 2×8) and progress the exercise up to NHE. Both ways of introducing the NHE should be able to mitigate some of the “novelty soreness” athletes will most likely have a day or two after.

Another point to consider is that the NHE research is typically done in 4 or 8 week prescriptions. Most soccer seasons are typically 3-4x the high end of that range. Is it viable to do NHE throughout the long season and continue to see positive adaptations in the hamstring? Maybe, maybe not. With a relatively untrained athlete adaptations could continue for quite some time because as a weak athlete gets stronger they are able to increase time under tension due to the ability to resist for a longer range of motion. If you like to use resistance bands to make it an assisted nordic, you could still take the exercise out for quite some time just by slightly manipulating volume and the intensity of the band assistance.

What if you have a very well trained and strong enough athlete? There are a couple of options that might suffice depending on who you’re working with. There are certainly more options, these ones tend to eccentrically overload the hamstrings to the greatest extent:

NHE + Additional Eccentric Load – (This is probably best done on a GHD). An athlete would hold a dumbbell or weighted object and lower slowly until they’ve reached the end point of the exercise and hand the weight off to a partner or coach and return to the top without the weight.

Single Leg NHE – This is a very intense version and too intense for most honestly, but it can be a viable option if the goal is to overload the hamstrings and the athlete can handle it. This would consist of lowering with 1 leg (the other leg is free and under no resistance) and lowering under control with a single leg. The same type of idea can be done with glute/hamstring bridges on sliders if a less advanced version is needed. The athlete can slide with two legs on the concentric portion and then lift one leg and continue the eccentric portion with one leg.

Drop-catch RDLs – Drop catch RDLs are an exercise where the athlete will start at the top of the RDL, release the bar slightly from the hands so it is free falling toward the floor, and With the hands still slightly around the bar, the athlete will follow the bar down and “recatch” in the bottom position of the RDL. This causes the hamstring to contract and brake violently to stop the bar from falling further toward the floor.

When we consider the amount of research that there is and the benefits from a performance and potential reduction of injury side from the NHE , we can’t neglect the fundamentals. Even if you don’t use the NHE, we have look at and understand what qualities the NHE is training and apply those concepts to other hamstring development exercises.

References:

Alvares, J., Marques, V., Vaz, M., Baroni, B. (2017). Four weeks of Nordic hamstring exercise reduce muscle injury risk factors in young adults. Journal of Strength & Conditioning Research.

Ethier, C. & Simmons, C. (2007). Introductory Biomechanics: From Cells to Organisms. Cambridge University Press.

Ema, R., Akagi, R., Wakahara, T., Kawakami, Y. (2016). Training-induced changes in architecture of human skeletal muscles: Current evidence and unresolved issues. The Journal of Physical Fitness and Sports Medicine.

Fernandez, D., Docampo-Blanco, P., Martinez-Fernandez, J. (2017). Changes in muscle architecture of biceps femoris induced by eccentric strength training with nordic hamstring exercise. Scandinavian Journal of Medicine and Science in Sports.

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