Nordic Hamstring Curls: Benefits, Risks, and Proper Technique for Knee Health

Are Nordics Good for Knees?

Nordic hamstring curls are an exceptionally effective exercise for strengthening the hamstrings, offering significant benefits for knee health, particularly in preventing anterior cruciate ligament (ACL) injuries, when performed with proper technique and appropriate progression.

Understanding the Nordic Hamstring Curl

The Nordic hamstring curl (NHC) is an advanced bodyweight exercise primarily targeting the eccentric strength of the hamstrings. Unlike traditional hamstring curls where the concentric (shortening) phase is emphasized, the NHC focuses on the controlled lengthening of the hamstrings under load. The exercise typically involves kneeling with the ankles anchored, then slowly lowering the torso forward, resisting gravity solely with the hamstring muscles, before using the hands to push back up or a partner to assist.

Primary Muscles Involved:

• Hamstrings (Biceps Femoris, Semitendinosus, Semimembranosus): These are the prime movers, working eccentrically to control the descent.
• Gluteals: Assist in hip extension and stability.
• Core Muscles: Essential for maintaining a rigid torso and preventing compensatory lumbar extension.

The Biomechanics of Knee Protection and Stress

The knee joint's stability relies heavily on the synergistic action of its ligaments and surrounding musculature. The hamstrings play a crucial role in dynamic knee stability, especially in protecting the ACL.

• Hamstring-ACL Relationship: The hamstrings act as knee flexors and hip extensors. When the knee is extending rapidly (e.g., during deceleration or cutting movements), the hamstrings co-contract with the quadriceps. This co-contraction helps to pull the tibia posteriorly, counteracting the anterior shear forces generated by the quadriceps that can stress the ACL. Strong, resilient hamstrings reduce the load on the ACL, lowering the risk of injury, particularly in sports involving sudden stops, pivots, and jumps.
• Eccentric Loading: The NHC uniquely targets the eccentric strength of the hamstrings. Eccentric contractions are crucial for absorbing impact, decelerating movements, and preventing muscle strains. Training the hamstrings eccentrically enhances their ability to withstand high tensile forces, improving their "braking" capacity and resilience against injury. This type of training also promotes beneficial adaptations in muscle architecture, such as increased fascicle length, which is associated with reduced injury risk.
• Knee Joint Stress: While the NHC primarily loads the hamstrings, the knee joint itself is subjected to compressive forces, especially at the patellofemoral joint, as the quadriceps (though not the primary target) engage isometrically to stabilize the knee during the movement. However, the forces are distributed, and for individuals with healthy knees, this stress is generally well-tolerated and contributes to overall joint robustness.

Benefits of Nordic Hamstring Curls for Knee Health

The evidence overwhelmingly supports the benefits of NHCs for knee health, particularly in athletic populations.

• ACL Injury Prevention: Numerous studies, including meta-analyses, have demonstrated that regular Nordic hamstring curl training significantly reduces the incidence of hamstring and ACL injuries in athletes across various sports (e.g., soccer, football, basketball). This is largely attributed to the enhanced eccentric hamstring strength and improved hamstring-to-quadriceps strength ratio.
• Hamstring Strength and Power: NHCs are unparalleled in developing eccentric hamstring strength, which translates to improved sprint performance, agility, and the ability to decelerate effectively. These attributes indirectly contribute to knee health by improving overall movement mechanics and reducing uncontrolled forces on the joint.
• Rehabilitation Aid: Under expert guidance, NHCs can be incorporated into later stages of rehabilitation for hamstring strains or certain knee injuries, helping to restore strength and function.
• Improved Muscle Balance: Strengthening the hamstrings helps to balance the strength profile between the quadriceps and hamstrings, which is vital for optimal knee function and reducing anterior knee pain.

Potential Risks and Considerations for the Knees

While highly beneficial, NHCs are a demanding exercise and come with potential risks if not performed correctly or if an individual is not adequately prepared.

• High Eccentric Load: The very nature of the NHC—high eccentric loading—means there's a risk of acute hamstring muscle strain or delayed onset muscle soreness (DOMS), especially for beginners or those not accustomed to this type of stress. This is not a direct knee injury but can indirectly affect knee function.
• Patellar Tendon Stress: While primarily a hamstring exercise, the quadriceps muscles must work isometrically to stabilize the knee, especially as the body approaches parallel to the ground. This can place some stress on the patellar tendon. Individuals with pre-existing patellar tendinopathy or "jumper's knee" should approach NHCs with caution or consult a healthcare professional.
• Improper Form: Compensatory movements, such as excessive arching of the lower back (lumbar hyperextension) or collapsing through the hips, can shift the load away from the hamstrings and place undue stress on the lumbar spine or other joints, reducing the exercise's efficacy and potentially increasing injury risk.
• Pre-existing Conditions: Individuals with acute knee pain, severe osteoarthritis, recent knee surgery (without clearance), or other significant knee pathologies should avoid NHCs or seek professional medical advice before attempting them.

Proper Execution for Knee Safety and Efficacy

To maximize benefits and minimize risks, meticulous attention to form and progressive overload is essential.

• Setup: Ensure your ankles are securely anchored (e.g., under a stable bar, by a partner, or using a dedicated Nordic bench). Place a pad under your knees for comfort.
• Controlled Descent: Begin with your body in a straight line from head to knees. Slowly lower your torso forward, resisting gravity with your hamstrings. Maintain a rigid plank-like posture; avoid hinging at the hips or arching your lower back. The slower the descent, the greater the eccentric load.
• Maintaining a Neutral Spine: Engage your core throughout the movement to prevent hyperextension of the lumbar spine.
• Partial Range of Motion (ROM) and Assistance: If full range of motion is too challenging, start by lowering only as far as you can control, then use your hands to push back to the starting position. A partner can also provide assistance by pushing on your upper back during the ascent. Progress gradually to a full range of motion.
• Frequency and Volume: Begin with low volume (e.g., 2-3 sets of 3-5 repetitions) once or twice a week, allowing adequate recovery. As strength improves, volume can be increased.

Who Should Consider Nordic Hamstring Curls?

• Athletes in High-Risk Sports: Particularly those involved in sports requiring explosive acceleration, deceleration, cutting, and jumping (e.g., soccer, football, basketball, rugby, track and field).
• Individuals Looking to Improve Posterior Chain Strength: For general fitness enthusiasts seeking to build robust hamstring strength.
• Those with a History of Hamstring Issues: As part of a structured rehabilitation and injury prevention program, under the guidance of a physical therapist or certified trainer.

Who Should Exercise Caution or Avoid?

• Individuals with Acute Knee Pain or Injury: Any sharp or persistent pain in the knee during the exercise is a clear signal to stop.
• Those with Very Weak Hamstrings: Beginners should start with less demanding hamstring exercises (e.g., glute-ham raises, single-leg RDLs) to build foundational strength before attempting NHCs.
• Individuals with Severe Lower Back Issues: The demand for core stability is high, and poor form can exacerbate lower back pain.

Conclusion: A Powerful Tool, Used Wisely

Nordic hamstring curls are an incredibly effective, evidence-based exercise for enhancing hamstring strength and significantly reducing the risk of hamstring strains and ACL injuries. For individuals with healthy knees and an appropriate strength base, they are undoubtedly "good for knees." However, due to their high intensity and eccentric demands, proper technique, gradual progression, and attention to individual physical limitations are paramount. When integrated thoughtfully into a training program, NHCs are a powerful asset for optimizing knee health and athletic performance.