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Nordic curls & injury prevention

Hamstring injuries are common in ball sports with explosive running patterns. But can also occur in sports that require maximum effort such as powerlifting. A hamstring injury can also occur in sports that require a lot of flexibility such as gymnastics or taekwondo. Symptoms of a hamstring injury can vary. Often there is a sharp pain immediately or shortly after the onset. In some cases, there is a snapping sensation. The pain is almost always easily localized and a bruise may appear within a few days. With both small tears and larger injuries, stretching the hamstring will trigger the symptoms. Hamstring injuries generally recover well. The only thing we often see is that the risk of a new hamstring injury is high. Within two months, 12-25% re-injures the hamstring. The biggest risk factor for a hamstring injury is a past hamstring injury. So it is important that you know how to prevent re-injury! In this blog, we're going to explain to you what a hamstring injury is and what your options are regarding injury prevention.

Anatomy of the hamstrings

The hamstrings is a group of muscles on the back of your thigh. This muscle group runs from your ischial tuberosity to both the inside and outside of your knee. The hamstrings is a bi-articular muscle group. This means that the muscle runs across two different joints. In this case, across the hip and the knee. Because the function of the hamstrings runs across 2 joints, the risk of injury is also greater. The hamstring's function is to bend the knee and extend the hip. Under fatigue or during the delivery of maximum power, it can sometimes go wrong in the control of the muscles and the pulling forces on the muscle are too great. 

The Latin names for the hamstrings are:

  • musculus semitendinosis
  • musculus semimembranosis
  • musculus biceps femoris

 

 Recovery from groin problems

Different types

hamstring injuries 

A hamstring injury is one of the most common non-contact injuries in various sports. We divide this injury into two different types. This classification is made based on the mechanism of origin:  

In type 1, there is an explosive moment for example as in a sprint. The forces on the muscle fibers of the hamstring are too great and damage occurs. 

In addition to sprinting, there are other examples where a type 1 hamstring injury can occur, for example: jumping, hurdling in athletics or a deadlift in powerlifting. In sprinting, we see that this injury often occurs at the moment when the foot is about to hit the ground. In this phase of the sprint pattern, the forces are at their highest. The muscle now fires at maximum but must also brake eccentrically to maintain good control of the knee and position of the foot on the ground. 

  • 12-16% of all injuries in professional soccer are hamstring injuries
  •  In 75% of the cases, the injury is to the biceps femoris

A type 2 hamstring injury is one where there is a lot of stretch on the muscle, often in gymnasts or dancers. This happens when the hip has to bend to the maximum and the muscle stretches excessively. In most cases, this is a less painful injury but the recovery time is often longer because the injury is in the upper part of the hamstring towards the tendon. This type usually involves injury to the semimembranosus.

We know that strength training can reduce the risk of injury. Getting stronger in the eccentric phase is especially important if you want to prevent hamstring injuries. Thus, stronger hamstrings reduce injury risk(1). Eccentric training also makes for anatomically longer muscle strings(2). Here we no longer mean that you actually get longer muscles. This is probably why controlled strength training does allow you to become more limber. A muscle bundle is defined as a bundle of multiple muscle fibers together. Athletes with longer muscle bundles are less likely to suffer a hamstring injury. 

A study conducted in September 2021 in recreational athletes shows that sarcomeres lengthen after 3 weeks of training with the nordic hamstring curl. This elongation in sarcomere length is most likely responsible for the longer muscle length. The exact explanation is still unclear(3). 

Training for less risk of hamstring injury

You can train your hamstring in two different ways:  

  1. Knee flexion 
  2. Hip extension 

An example of a hamstring exercise in knee flexion is the nordic curl. The Nordic curl reduces the risk of hamstring injury by an average of 50%(4). This exercise is also seen more and more on the training fields, for example in the preparation of a season. With this exercise you train mainly the eccentric phase of the hamstring. You deliver power while the muscle lengthens. 

An example of a hamstring exercise more focused on hip extension is the romanian deadlift(RDL). It is much easier to focus on eccentric phase with the Nordic curl than with an RDL. It is technically an easy exercise. You can reap the benefits of the nordic curl over the RDL more quickly for this reason.


But the RDL has two strengths when compared to the Nordic curl: 

  1. More emphasis on biceps femoris 
  2. More stretch on the hamstrings than in the Nordic curl

Let it just be the biceps femoris that is most susceptible to a muscle injury. It is then useful to do an exercise where this is also trained the best. When you can train a muscle in a wide range so full length we see changes in muscle length (only in the muscle bundle). With that in mind, it makes sense to see if an RDL can be just as effective, or perhaps more effective, compared to Nordic curls.

Conclusion

For optimal results, it is good to include both variations in your program. A Nordic curl is a great exercise to train strength in the hamstrings. When you only do Nordic curls you miss exercises that train the hamstrings in a (fully) stretched position. An RDL where muscle bundles are loaded at full length is then a good choice. If you were to get much stronger in your RDL, this is also probably more effective than just a Nordic curl. But really building in weight for an RDL takes time. Think about grip strength and the more difficult technical execution of a compound exercise. Like a hyperextension, for example, the Nordic curl is an easy exercise to perform with a fast learning curve. This makes it faster to progress in strength in the hamstrings. Therefore, keep doing Nordic curls but in the meantime become a king in the RDL. This increase in strength in the hamstrings can make an injury less likely to occur. Unfortunately, truly preventing injuries can never be done. We are dealing with too many factors that can potentially contribute to the occurrence of an injury. So there are no guarantees! Increasing the load capacity in the hamstrings through strength training is certainly a good start! You do not sprint with two legs at the same time. Therefore, it is also wise to introduce unilateral exercises into your program. This means with one leg. So in addition to the standard version, also do a unilateral form of the RDL and possibly the Nordic Curl. If you are not ready for this, because these exercises are heavy, then use a roman chair or a hyper extension. Good Luck!

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