Over the last few years, you may have seen very strong athletes perform Nordic Curls (glute ham raise done on the floor) on multiple social media platforms to tout their athletic prowess, and to demonstrate the strength of their hamstrings.
In this research article, I’ll go over what Nordic hamstring curls are, and share with you common prescriptions for them, the efficacy behind the exercise, and whether or not if you are competing in competitive sports you should or should not be using them.
What Are Nordic Curls and The History
The Nordic Curls were first written back in the 1880s by George Herbert. But the posterior chain and hamstring work was made popular by Vasily Alekseyev. He is the famous super heavy 1972 and 1976 Olympic gold medalist who set 80 world records and 81 Soviet records.
Vasily implemented his well-known techniques of barbell back extensions including the pommel horse back extensions and back extensions over a horse with his feet being anchored to his training apparatus. These variations became popular in North America back then.
Then Dr. Michael Yessis invented the Glute Ham Raise (GHR) machine and those who can’t afford it improvised by executing the GHR from the floor which made it look “cool”. This technique has been around since the 1880s.
You get a badge of honor if you perform Glute Ham Raise (GHR) slowly or come close within a centimeter from your chest or nose to the ground. That’s a real show of strength as the hamstrings have to be tremendously strong to perform such technique. That’s isometric and static in nature hence tremendous time under tension.
Understanding that this exercise is isometric and static in nature, is that really beneficial or transferable for athletes in explosive/dynamic sports like football, basketball, soccer, volleyball, hockey, tennis, baseball, etc.?
I’ve put together the research below to break it all down, but to truly understand it, let’s first look at history to see why the Nordic Curl has become trendy.
What Made Nordic Curls So Popular
Crossfit made Nordic Curls popular. I like the fact that crossfit is a hard-working culture that focuses on the whole body instead of isolated bodybuilding movements, but oftentimes we sacrifice what is right with what will go viral. And Nordic Curl is one of those impressive exercises that went viral with tons of celebrities, athletic superstars all posting their Nordic Curl challenge over the internet.
The focus on getting strong hamstrings through nordic curls spread like wildfire because it’s cool and it makes sense on the surface.
Nordic Curls was also popular because a few researchers emphasized the importance of strength by measuring quad to hamstring ratios seated on a leg curl machine, which unfortunately later was proven to have no transfer to running and sprinting.
I’ll dive deeper into this with research below.
When Are They Commonly Prescribed?
A common process for trainers, coaches, and medical practitioners is to prescribe strengthening exercises to a weak area. So if someone comes in with weak hamstrings or had a previous hamstring injury, one prescribes more hamstring work, typically isolated, to address the issue. If someone came in with a weak chest, one will prescribe more isolated chest exercises.
While this thought process may sound like common sense, it neglects the principle of the body being all connected, and that you must work the entire chain to build proper communication on a cellular level.
Since Nordic Curls are mainly touted as a safe exercise to do at home or at a gym. Many novice trainers, coaches will also prescribe them because it hits two good points. It’s easy to do without supervision, and the athlete (or the client) feel like they are addressing the issue even though it may be actually counterproductive for the long run.
The Efficacy Behind Nordic Curls
With all the money we have available in sports, well-known evidence-based preventive measures, increase in medical practitioners we have globally, and the popularity of Nordic Curls for athletes, you may assume hamstring injuries are on a decline, but they are actually on a rise (almost 4% per year since 2001).
In this section of the article, the research team and I dive deep with more scientific jargon, so if it’s too long to read (TLDR), skip to the next section below for Our Recommendation and Better Alternatives to Nordic Curls.
Researchers emphasize the importance of quad to hamstring ratio as an indicator of performance?
A number of studies have examined the H/Q (hamstring/quadriceps) ratio (Komi, 1992). Limitations to this ratio from the literature include:
- The peak rotational force (torque) of the hamstrings and quadriceps is dependent on the angle of the knee joint. Many reports do not clearly state the type of measurement.
- There are large individual differences in the H/Q ratio dependent on the health of the knee joint.
Many believe that the optimal strength ratio for healthy hamstrings is 60/40. This data unfortunately was taken into the wrong context and started targeting and isolated the exercises for their hamstrings and quads. Hence why Nordic Curls became a go to exercise if you used the data without context.
They are derived from one popular paper in 1955 by (Steindler. A) Kinesiology of the Human Body under Normal and Pathological Conditions.
The method of testing the hamstring quad ratio seated goes against two rules:
- Strength is specific
- It’s all connected
The muscles work in unison so it’s nonsensical to isolate a single muscle group in this manner and not abide by posture specific laws of strength.
Does it translate to an athlete standing or sprinting? No, it does not and cannot.
According to Tesch (1993) the biceps femoris is not involved in seated leg curl. Yet this muscle is most frequently cited as the site of hamstring pulls: “gracilis, sartoris, semitendinosus show marked involvement in this exercise. Surprisingly, the biceps femoris is not”.
Is isolation and compartmentalization of muscle groups causing more bad than good?
In short, yes.
It is a major issue when the Therapy and Core Stability Community’s obsessiveness to isolate, compartmentalize, and train individual muscle groups, instead of working these muscles in unison.
Teaching the muscles different languages and trying to get them to communicate with one another is not going to happen. There will be miscommunication and oftentimes this comes into play with none choreographed, black swan circumstances incidents or simple quick and explosive movements.
Always remember that strength is specific. The body will adapt specifically to the nature of the stimulus imposed.
“To strengthen the hamstrings and prevent tears or ruptures, start training muscle groups synergistically to full range of motion” – Alan Warner, Strength Coach, AASc
Is prolonged tension in the hamstrings creating injurious effects on the body?
Yes it is. The agonists and antagonists consistently switch in a coordinated manner when we sprint. Nordic Curls disrupt this coordination of contraction and relaxation as it promotes prolonged tension in the hamstrings. Thus stretching and lengthening just before ground contact, the “Natural Strategy“ (Vera-Garcia, 2007) of sprinting is disrupted.
Strength and muscle coordination patterns are specific and by extension the neurological language/stimulus given to muscles is specific to how they will perform.
The Nordic Curls is undoubtedly a contraindicated exercise for the hamstring and here’s why:
- The Nordic Curls is the slow grinding nature of knee flexion including slow eccentric extension segments that are inconsistent with the actual dynamic functions of muscle contractions in sprints.
- The knee and ankle joints are fixed when performing Nordic Curls, but they are in constant motion when you sprint.
- Contraction of the gastrocnemius and other ankle muscles (i.e. peroneals and posterior tibialis) are shortened to flex the knees. This is incorrect because the muscles should be trained to lengthen and stretch before ground contact along with the bi-articular muscles (i.e. biceps femoris, semitendinosus, semimembranosus, gracilis and plantaris). The muscles involved in lengthening should also not be subjected to heavy grinding loads (slow contractions prior to ground contact). This is clearly contraindicated to this segment of sprinting.
- The muscles that cross the joint in the knees and ankles are being trained to shorten which is inconsistent with the actual dynamics of sprinting and running.
These four contraindications scream one word: coordination.
In my opinion, the lack of neuromuscular coordination is the top reason that many athletes suffer from these hamstring injuries, and nordic curls are the antithesis to neuromuscular coordination for athletes in dynamic sports.
Efficient springs means efficient sprinting.
In the book The Human Machine: How the Body Works, R. McNeill Alexander explains that only 7% of the heat is lost and 93% of the work or energy returned when the tendon is stretched. In this respect, a tendon is as good as most rubbers, but not as good as steel springs.
The muscles surrounding the knees and ankles are like springs when we run—like a child on a pogo stick or a bouncing ball.
While the muscles can stretch to 3%, the tendons can stretch up to 9%, making the tendons vital in sprints. Hence, efficient springs means efficient sprinting.
So do the Nordic Curls help with the optimal relationship between the muscles and the tendons? Do Nordic Curls help tendons behave like springs?
The answer is no.
So what are the consequences?
“Coordination to a great extent is the active relaxation of muscles” – Y. Vershansky, 1988
Track coaches who are supposed to specialize in speed advising strength coaches to have the athletes perform seated rows on a machine during the competitive season are a major problem.
They have no concept of the role muscle relaxation plays in the production of speed.
Seated rows on a machine makes athletes slow, tight, and tense. It is the antithesis of speed development. Involuntary and volitional relaxation must be the priority.
In theory, the less overall muscle tension the lower the level of what Russian Sports Scientists refer to as internal resistance to muscle work. This means one does not resist its kinematic links as much as one who has created a high tension environment by too much bodybuilding exercises.
When the tendons are performing optimally, the muscles do not have to work as hard and as fast (i.e. contraction and stretching).
The muscles need to lengthen further and faster during explosive movements when the tendons are tight, dry, or mummified. This results in imbalance of the muscle and tendon apparatus.
It is clear that muscles use less energy when lengthening as opposed to shortening, which disrupts the mechanism as the muscles should be using less energy in this process. This is what the Russian Sports Scientists call the Negative Internal Resistance.
Low internal compliance of muscles and tendons leads to the consequences: hamstring tears, pulls, and ruptures.
These injuries plague collegiate and professional sports today and will continue to unless drastic changes are made to the specific application of strength training across sports.
“Muscles lose energy less fast acting as brakes than when holding constant length.”
In the application of training methods, one must consider the outcomes of prolonged isometric and constant tension on muscles in regards to performance in fast reacting explosive sports.
“If the average tension required of the muscle is reduced they will use less energy.”
It is clear that by reducing tension required, the muscles will use less energy, then it is also imperative we take into account the application of training methods that increase muscle tension internally thus making everything harder for the athlete.
A good example would be body building methods and the array of slow constant, isometric core exercises.
“This causes (prolonged straining) too much excitation in those groups of muscles which should be relaxed during this action. Unnecessary tension in these muscles creates additional resistance for the working muscles, reducing the speed of contraction and accelerating the onset of fatigue.” – Falameyev, A. I., Salnikov, V. A., Kimeishei, B.V., 1980. Translated by Andrew Charniga.
The foot is a spring – Not as good as a spring as the achilles tendon with 20% of heat energy lost, as where the achilles is only 7% (The Human Machine, by R McNeil Alexander) but the foot is still a spring that is connected to the leg spring and should not be restricted or compartmentalized because all muscles, ligaments, and tendons are connected, inter-connected, intra-connected, and work together.
The more we seek to disrupt nature/s mechanisms with arbitrary exercises the more complications we run into.
Too many restriction points will blow you up.
I see many injury prevention exercises with one of these joints hip, knee, or ankles fixed which is clearly not posture strength specific.
Sprinters are up right as most sports and all joints are free with no restrictions or locked into some apparatus.
Also there is no account or understanding anywhere universally that the most active muscle in sprinting is the tibialis anterior which does not cross the knee but can flex the knee through a mechanism called inertia coupling (Zajac, 2002).
Inertia coupling is a mechanism in which a single articular muscle acts on joints above or below the muscle joint it does not cross.
Nordic Curls restrict this vital muscle that’s most active in sprinting.
Another extraordinary salient factor is the assumption that a sprinter’s hamstrings are weak despite the fact that when running, jumping, stopping, cutting and evasive maneuvering all the muscles of the lower body are in play, connected and moving together.
But this fact is not considered and special exercises specifically for the hamstrings are made up, touted and sought after. Various papers and EMG studies have shown that the tibialis anterior as the most active in sprinting, while the common injury in sprinting is the hamstrings, specifically the biceps femoris.
The lack of attention and mention of the tibialis anterior being the most active muscle means the major contribution from this muscle is being ignored.
The more we disrupt this contribution of the tibialis anterior with straitjacket exercises (isolated and restricted), the more problems the athlete will run into over time.
If you are participating in sports that require explosivity such as Football, Soccer, Basketball, Baseball, Tennis, Volleyball, Lacrosse, Cricket just to name a few, then we’d strongly advise you to avoid Nordic Curls.
Earlier in the article when I was explaining what Nordic Curls were, I shared a video of Tyreek Hill performing an impressive 10 Nordic Curls in May 2020. Even doing one is an impressive feat, let alone 10. This exercise was quickly introduced into his daily and weekly routine with the notion it will make his hamstring strong. Unfortunately, it had the opposite effect. By August 2020, Hill left the Chiefs’ training practice with a hamstring injury. In December 2020, Hill missed the season finale suffering from another hamstring injury. In August 2021, another hamstring injury, and in October 2021, Hill suffered a quad injury.
When a National team Bobsledder had felt hamstring issues, he notified the team coach, and he was prescribed Nordic Curls by the medical staff. Initially, it seemed fine, but over time, he suffered more and more hamstring issues.
A national 100m sprinter was sidelined for years with one hamstring pull or strain after another. Medical practitioners diagnosed that his hamstrings were weak and prescribed a progressive protocol of nordic curls, glute ham raises, barbell glute bridges, balancing on stability balls, lateral band walks, clam shells and forward walks. While continuing to be on this so-called rehab program, issues continue to appear and worsen as more time passes.
There are tons more case studies just like this from amateur athletes to professional athletes. In the next section, I’ll share a few examples of what we’ve done to help the athletes remap their body to reprogram the connection in the body on a cellular level.
Better Alternatives to Nordic Curls
To get a better understanding of alternatives you may consider, it’s important to know one simple principle: the body is connected. The agonists and antagonists both need to be trained to work together to absorb forces, store that energy, and redistribute that kinetic energy effectively.
There is no one superior exercise that will do it all, and everyones’ situation, limitations, injury history are different so I’ll give you some examples of what we had done for some athletes, and their results.
For the national bobsledder who was suffering hamstring issues, I replaced all the nordic curls, glute ham raises with barbell jumps, and split squats. The result after 6 weeks, his hamstrings were feeling much better and responding to high speeds in a favorable manner and continued to be healthy for years.
The national 100m sprinter was referred to us as the isolated, compartmentalized approach by the medical practitioners was not working. He needed synchronization of all the muscles in his lower extremities. We threw out all band work, shortened range of motion work, and isolated work. We approached it with loaded mobility work, barbell step ups low box, barbell step ups high box, dumbbell step ups high and low box, etc. As we ramped up to prepare for the indoor season, his intensity in speed increased and he was amazed how he felt. After not competing in a year, he had an amazing come back and without injuries making it to the nationals.
Athletes must sparingly implement nordic curls.
We would completely get rid of the exercise in an athletes’ training regime altogether.
The concept and understanding that we are going about training the hamstrings the wrong way by constantly focusing on strength, when one should be focusing on coordinational strength not uncoordinated strength.
The Leg Spring is One! One cannot separate, compartmentalize and isolate through specific targeted exercises especially for the purpose of strength development.
Anything you do affects another.
The calves and the soleus are attached to a major spring.
The achilles tendon which is attached to the calcaneus which all act together as a unit with numerous muscles above and below the ankle, knee and hips.
The body being all connected performs movements through mechanisms of a complicated symphony. Do not disrupt this symphony.
Here at LPS, we spend many off-seasons Remapping™ (an advanced neuromuscular training) high level athletes who have disrupted this symphony while they were younger and misinformed. Oftentimes it takes 2 to 3 off-seasons to fully un-mummify the bad patterns, training, and bring proper communications back on a cellular level for their muscles, joints, ligaments and tendons.
If you are fortunate enough to be reading this at an earlier age, it’s not too late to think differently and properly. Here is a deep research and principles you must follow to develop that elite level strength, power, speed, but more importantly minimize your chances of suffering a career ending injury in your sport.