Nordic Curl Risks: Harmful Exercise Insights

Zera: Unraveling the Mystery of Nordic Curls

The strength-training community has always been enamored with trends that provide a competitive edge. From the Nautilus machine in the 1970s to jump shoes in the 1980s, skateboarding in the 1990s, and now Nordic curls – an exercise touted as the ultimate solution for preventing hamstring injuries, especially for sprinters.

But hold on. Let’s take a closer look.

Dr. Don Chu, a renowned high jump coach and weight training expert, introduced me to the Nordic Curl in a weight training class back in the early 1980s. More recently, the exercise has been made popular again by Ben “Kneesovertoesguy” Patrick. His knee rehab program featuring Nordic curls has attracted a huge following with over 1.3 million subscribers on YouTube and an appearance on Joe Rogan’s show.

Mastering the Basics of Nordic Curls

The first step in Nordic curls is to kneel on a mat with your feet secured by a partner. For added comfort, German sports scientist Dr. Tobias Alter recommends bringing your knees to the edge of the mat. Hands can be placed on your chest or at your sides, but for optimal control, keep them bent in a push-up position. This technique helps keep the hamstrings highly activated and allows you to catch yourself at the lowest point.

Start in an upright position with your thighs perpendicular to the floor, bringing your torso and legs down as one unit. When it becomes uncontrollable, catch yourself with your hands and then explosively bounce off the ground back to the starting point.

Nordic curls are extremely challenging due to their resistance curve. It’s difficult for an untrained athlete to complete a single repetition without crashing in the middle, let alone return to the starting point without help. In Dr. Chu’s class, only one elite male long jumper completed a full Nordic Curl, while a female discus thrower and national weightlifting champion came close to the goal.

Challenge Yourself

To become proficient at the movement, start by reducing your range of motion by placing a low platform in front of you. As you gradually build strength, you can gradually lower the height of the platform. Elastic bands can also be used to adjust resistance and help during the most challenging parts of the movement.

For gyms with state-of-the-art equipment, a Nordic curl machine like the Westside Inverse Curl machine® can provide a customized experience. These machines come with padded counterbalance arms that can be progressively adjusted to your strength profile.

At advanced levels, resistance can be increased by placing a weight plate on your chest or wearing an undershirt with weights. For beginners, it’s best to use additional resistance only during the descending phase and release the resistance during the ascending phase.

Common variants

  1. Fixed sit-up board: Use a sit-up board to hold your feet in place.
  2. Elastic band assist: hold the band at the limit range for added support.
  3. Curved bench: work out on a curved bench with padding for increased comfort.

There is no doubt that Nordic curls are very effective, but like any other exercise, they must be implemented carefully. If you’re interested in how similar exercises can contribute to overall physical development, try utilizing the grab bar hard pull to get in shape. Stay tuned as we delve into the science behind the efficacy of these exercises.

Nordic Curl and Sprinting: A Critical Perspective

Drawing on expert insights and research, Zera explores the controversial Nordic curl and its impact on sprinting performance and injury risk.

The anatomy behind the controversy

Renowned weightlifting sports scientist Andrew “Bud” Charniga has been critical of athletes training for the Nordic Curl. He recognizes the potential value of this type of training for bodybuilding, but believes its use for athletic training is questionable. His main concern was the anatomy and function of the calf muscles, particularly the gastrocnemius (upper calf) and the flounder (lower calf).

The gastrocnemius has a dual role in that it overlaps the knee joint and contributes to knee flexion. This anatomical feature has significant implications for stretching and muscle strengthening exercises. Example:

  • Stretching: Tight calf muscles can limit the effectiveness of hamstring stretching . Bob Anderson , author of Stretching, emphasizes the importance of relaxing the calf before performing stretching exercises that target the hamstring for optimal flexibility.

  • STRENGTHENING: Legendary strength coach Charles Poliquin utilized this knowledge to enhance hamstring activation during leg flexion. By activating the gastrocnemius muscle through dorsiflexion of the foot during leg raises and plantar flexion during the lowering phase, athletes can isolate the hamstrings for more effective centrifugal training.

Understanding the complex relationship between the calf and hamstring can improve training outcomes. However, from a motor learning perspective, Charniga believes that Nordic curls pose a significant risk to sprinters.

Risks for sprinters

In sprinting, hamstring injuries are most common late in the swing – when the front leg is fully extended and about to hit the ground. During this critical phase, the long head of the biceps femoris undergoes the greatest stretch. To avoid injury, the gastrocnemius muscle must remain relaxed to prevent reactionary forces that could strain the hamstring.According to Charniga, Nordic curls disrupt this coordination and increase the likelihood of injury.

The occasional Nordic curl challenge may not hurt, but for elite athletes, its cost-benefit ratio is questionable.

The age of misinformation

Nordic curling is growing in popularity online, with influencers touting its benefits and citing supportive studies. However, a closer look at these studies reveals mixed results. The systematic review titled “Impact of injury prevention programs including Nordic hamstring exercise on hamstring injury rates in soccer players: a systematic review and meta-analysis” highlights the need to critically evaluate claims.

Although the sport may be useful in some situations, Zella recommends a cautious approach, especially for high-level athletes for whom performance and safety are of paramount importance.

Do Nordic curling exercises really prevent hamstring injuries?

A study designed to simplify the understanding of injury prevention by reviewing multiple studies concluded that “teams that used an injury prevention program that included Nordic hindquarter (NH) exercises had a 51% lower rate of hindquarter injuries over the long term compared to teams that did not take preventive measures.” This finding is noteworthy, but a closer look at the methodology raises questions.

Only five studies met the researchers’ criteria, and only one of those included Nordic curling exercises as the sole intervention. Below is an example of an intervention program from one of the studies under review:

Hamstring training

  • Initial running training

    • Hip adduction
    • Hip adduction
    • Glute abduction
    • Circle Partner
    • Shoulder contact
    • Cut and return
  • Exercises

    • Plank Support
    • Lateral Plank Support
    • Single Leg Balance
    • Single Leg Balance
    • Squats
    • Jumping
  • Final Running Workout

    • Sprint
    • Tangential lateral

With such a variety of workouts, how can we differentiate between the effects of Nordic curling? Reducing the incidence of injuries may not be related to Nordic curling, as mentioned in the study , “Because we did not quantify physiological variables, we were unable to adequately determine the cause of the reduced risk of injury or to identify the most effective components of the intervention program.”

As for the only study in which Nordic Curl was the only variable, the results were unsatisfactory. The researchers noted that Nordic curls “did not reduce the severity of hamstring injuries.”

Review of Studies

There are numerous studies on Nordic curling, but many of them need to be examined carefully.In a 2022 review, Dr. Alt highlighted that “assessments and interventions suffered from inaccurate reporting or a lack of information about how Nordic hamstring exercise (NHE) was performed and analyzed at follow-up.”

In a conversation with Dr. Alt, he explained in detail , “The way most people perform traditional Nordic curls is not used to its full potential because only 30% of the impulse is used for anterior 45-degree knee extension. The knee extension angle should be increased through assistance or coaching to obtain high intensity training for better performance and injury prevention.”

Real-World Evidence

While the Nordic Curl is widely recognized among strength coaches and researchers, where are the real-world success stories?

For example, a study involving 2,022 soccer players showed that athletes from 54 teams in 20 European countries (2001-2022) showed a worrisome trend over this time period: the rate of muscle strains doubled. The rate of muscle strains has risen over the past eight seasons, both in training and in games.

The situation is similar in American soccer. Hamstring injuries still exist in the NFL, despite the realization of the dangers of Nordic curls. Each week, about 24 players are kept off the field by hamstring problems. Example:

  • Before the start of the 2019 season, 43 players were unable to play due to hamstring injuries.
  • From 2018 to 2019, an average of 25 players missed games each week due to hamstring injuries.

This trend continues unchecked.20 In October 2023, a study by Charniga reported that 48 NFL players were unable to play due to hamstring injuries in a single week.

Conclusion.

Although Nordic curling has been touted as a solution to “bulletproof” hamstrings, the increasing prevalence of hamstring injuries across a wide range of sports begs the question of its effectiveness. Could it be that this famous exercise is not as universally effective as is often claimed?

Revisiting the value of Nordic curling: five key variables

When evaluating Nordic curls from an evidence-based perspective, it is necessary to consider five key variables that call into question the role of Nordic curls in enhancing athletic performance.

1. Biomechanics.

The principle of wholeness emphasizes that the whole is greater than the sum of its parts and emphasizes connectivity in movement. Unlike the holistic function of the hamstrings in sprinting, Nordic curls only work knee flexion and extension. This separation training may be beneficial for bodybuilders, but it runs counter to the biomechanics of running.

A 2018 study in the Journal of Medicine and Science in Sports and Exercise confirmed that the hamstrings stretch at both the knee and hip joints during sprinting. In contrast, the Nordic Hamstring Exercise (NHE) only stretches the knee. a 2019 study on Australian Rugby Football (ARF) further concluded that the NHE lacks practical application in dynamic sports. In addition, the immobilization of the NHE prevents movement of the ankle muscles that are vital during running and jumping, thus limiting its athletic adaptations.

2. Force generation

The slow and controlled movement of Nordic curls promotes muscle hypertrophy but does not enhance the connective tissue elasticity required for explosive power. Constant tension during exercise alters muscle fiber organization (pennation angle) and reduces rapid force output.

High-speed sports such as sprinting rely on short, intense bursts of force followed by rapid muscle relaxation. As Dr. Stuart McGill, an expert in spinal biomechanics, notes, good sprinters and weightlifters excel at contracting and relaxing their muscles efficiently, and Nordic curls don’t develop this ability. For these reasons, the sport is more suited to bodybuilding than athletic development.

3. Strength and Function

The force generated during sprinting can be up to eight times your body weight, and while Nordic curls are commonly used to cope with such large forces, their actual effectiveness is limited.A 2021 study reported that the peak force generated by the hamstrings during Nordic curls could not be compared to that generated during sprinting.

Additionally, a 2019 study found that Nordic curl training produced only negligible improvements in sprinting performance.Another 2017 study observed an increase in posterior hamstring mass after a six-week training program, but no significant gains in centrifugal strength, highlighting the limitations of Nordic curl training in replicating the demands of sprinting.

4. Elasticity and speed

Sprinting requires elasticity and a pulsatile movement pattern, i.e., faster to exert and faster to relax. Russian sports science emphasizes that elite athletes demonstrate superior relaxation, a trait that Nordic curling does not develop.

5. Alternatives

While Nordic curls may help prevent hamstring injuries, they should be used with caution. For a more athletically practical alternative, flywheel training is a good choice, especially if sprint training is not possible due to environmental constraints. For those who want to enhance their jumping ability, exploring weight training can provide an effective strategy.

In conclusion, while Nordic curling is useful in specific situations such as bodybuilding, it still has limited effectiveness as a tool for improving athletic performance. Prioritizing exercises that mimic the dynamics of a specific sport can provide greater benefits to the athlete.

Nordic rolls: an in-depth look at their limitations and alternatives

Centrifugal strength and sprint performance
Contrary to popular belief, the Nordic Curl is not as effective at improving sprint performance or developing centrifugal strength as the sprint itself. While centrifugal contractions produce the highest levels of muscular strength, advanced tools such as flywheel devices are better at delivering centrifugal overload. These devices amplify concentric forces and push athletes to reach peak centrifugal contraction quickly. For example, workouts that incorporate kBox flywheel training allow for unsupported and assisted movements that optimize strength generation. When stability is increased, such as when gripping a barbell, athletes can generate greater force. This suggests that unsupported squats can be combined with supported squats for maximum strength gains in specialized training.

Range of motion: a misconception
Many influencers claim that Nordic curls strengthen the hamstrings throughout the range of motion – this is inaccurate. The exercise begins with the thighs perpendicular to the ground, which in itself limits the range of motion of the biceps. In contrast, supine leg curls use cables or roller boards to bring the heels closer to the buttocks, thus providing resistance throughout the range of motion. In addition, these variations allow the legs to rotate internally and externally, promoting balanced muscle development. Unlike Nordic curls, these exercises avoid a rigid movement pattern and reduce stress on the patella.

Additionally, in Nordic curls, gravity acts vertically and does not create resistance until the movement is performed. Interestingly, elite bodybuilders often use partial-range exercises to overload various points of the strength curve, which effectively changes the straightening angle of the hamstrings and improves strength output.

Exercise Applications and Testing
The Nordic Curl is occasionally used for strength assessment, but its actual value is questionable. What exactly does this exercise test? Calf or hamstring strength? Furthermore, how does this exercise translate into athletic movements? Few exercises can replicate the motion of the lower leg not moving while kneeling – perhaps kayaking comes closest. This lack of functionality limits its use in athletic training.

Knee Stress Considerations
As an isolation exercise, the Nordic curl concentrates stress on a single structure rather than spreading it over multiple joints. In contrast, compound movements can effectively distribute forces, reduce localized stress, and potentially reduce the risk of injury. This isolation further highlights the limitations of the Nordic curl as a sports performance training tool.

Conclusion.
Although Nordic curls have a place in targeted training, their limitations in terms of range of motion, functional application, and centrifugal strength development make them less flexible than alternatives such as flywheel training or leg curls. In order to fully develop the hamstrings and improve athletic performance, more movements must be incorporated.

Expert insights on Nordic curls: a controversial athletic workout

Renowned posturalist Paul Gagné, who has worked with more than 500 NHL players and with Dr. Guy Voyer, a distinguished osteopathic physician known for his knee injury seminars, has strong reservations about Nordic curls. According to Gagne, these exercises place undue stress on the hamstrings (the key muscles responsible for knee stability), especially in the bottom position, where control and safety are often compromised.

Gagne states, “The hamstrings are under tremendous stress, especially in the lowest phases of the movement, when the knee is most vulnerable. Poor technique is common, and lack of control at this stage poses a significant risk.” He also warns that the Nordic curl puts considerable pressure on the meniscus, which can lead to chronic inflammation such as prepatellar bursitis, also known as ‘maid’s knee’.

The problem with viral fitness trends

The rise of social media has provided unprecedented access to fitness information, but it has also spread a great deal of misinformation. While some influencers and even some studies have claimed that this type of exercise has significant benefits for improving performance and preventing injuries, the reality is often different. Nordic curling is one such example of an exercise that claims benefits that may not justify the risks.

Rethinking Nordic curling

Nordic curls have gained popularity as a hamstring injury prevention exercise, but experts like Gagne advise caution. Improper practice and the biomechanical stress it puts on the knee can outweigh any potential benefits.

Building Better Athletes with Zera

At Zera, we are committed to providing actionable, evidence-based insights for athletes, coaches, and sports scientists. Our mission is to weed out the faddish fitness advice and provide practical solutions that improve athletic performance while ensuring safety.

References.

  • Alt T, personal communication, 1/4/24.
  • Charniga B. “Hamstring Injury: Prophylaxis Fallacies in Sport,” Sportivnypress.com, 6/29/21.
  • Al Attar WSA et al. “Impact of an injury prevention program including Nordic hamstring exercises on hamstring injury rates in soccer players: a systematic review and meta-analysis. Sports Medicine. 2017 May;47(5):907-916.
  • Alt T et al. “What is the status of Nordic hamstring exercise-related research? -A scoping study reveals the need for improved methods and reporting.” International Journal of Public Health Environmental Research. 2022 September 7; 19(18).
  • Ekstrand J. “The rate of hamstring injuries has increased in recent seasons and now accounts for 24% of all injuries in men’s professional soccer: the UEFA Elite Club Injury Study 2001/03 to 2021/22. British Journal of Sports Medicine. 2022 Dec 6;57:292-298.
  • Afonso J et al, The hamstring: anatomical and physiological variations and their potential relationship to injury risk, Frontiers in Physiology, July 7, 2021; 12
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  • Li L and Minh Nguyen, “Nordic Exercise Should Not Be Used to Predict Hamstring Injury Models,” Special Communication. Sports Medicine and Science. 2018 Dec; 50(12).
  • Milanese S et al. “Hamstring injuries and Australian rugby: over-reliance on Nordic hamstring exercises as a preventive measure?” Journal of Sports Medicine. 2019 July 23; 10:99-105.
  • McGill S. “An Approach to Pain-Free Training for Track Athletes with Stuart McGill.” Zera Insights. 12/1/2023.
  • Ruan M, et al. “The Relationship Between the Contact Force at the Ankle Hook and the Hamstring Muscle Force During the Nordic Hamstring Exercise.” Frontiers in Physiology. March 9, 2021;12.
  • Freeman BW, et al. “The effects of sprint training and the Nordic hamstring exercise on eccentric hamstring strength and sprint performance in adolescent athletes.” Journal of Sports Medicine and Physical Fitness. July 2019;59(7):1119-1125.
  • Alt T et al. “What do we seek in hamstring centrifugal training: specific angle control or supramaximal stimulation?” Journal of Sports Rehabilitation.
  • Zera, 2023;32(7):782-789.
  • Pacek A. Personal communication. 12/20/23.
  • Gagné P. Personal communication. 12/15/23. for those looking to improve athletic performance, understanding and applying relevant strength standards is critical to success.

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