Hamstring Curls: Types, Step-by-Step Guide, Benefits, and Mistakes to Avoid

How to do leg bicep curls?

Leg bicep curls, more accurately termed hamstring curls, are isolation exercises designed to strengthen the posterior thigh muscles – the hamstrings – through knee flexion, crucial for lower body power, injury prevention, and athletic performance.

Understanding "Leg Bicep Curls": The Hamstring Connection

While often colloquially referred to as "leg bicep curls," the primary muscles targeted are the hamstrings, not the biceps brachii of the arm. The hamstring group consists of three distinct muscles:

• Biceps Femoris (long and short heads): Located on the lateral (outer) side of the posterior thigh.
• Semitendinosus: Located on the medial (inner) side of the posterior thigh.
• Semimembranosus: Lies deep to the semitendinosus, also on the medial side.

These muscles originate from the ischial tuberosity (sit bones) of the pelvis (except for the short head of the biceps femoris) and insert around the knee joint. Their primary function is knee flexion (bending the knee) and hip extension (moving the leg backward), making them antagonists to the quadriceps femoris. Strengthening the hamstrings is vital for balanced lower body development, preventing common injuries like ACL tears and hamstring strains, and enhancing performance in activities requiring running, jumping, and explosive leg drive.

Types of Leg Bicep Curl Exercises

Leg curl variations typically involve specialized machines that provide resistance against knee flexion. The main types include:

• Lying Leg Curl: Performed face down on a bench, allowing for a strong hamstring contraction with minimal hip flexor involvement.
• Seated Leg Curl: Performed seated upright, which places the hamstrings in a slightly lengthened position at the start, potentially emphasizing different parts of the muscle.
• Standing Leg Curl: A unilateral (one leg at a time) exercise, often performed on a machine or cable pulley, which helps address muscular imbalances.
• Nordic Hamstring Curl: An advanced bodyweight exercise that involves kneeling and lowering the torso forward, offering a high eccentric load.

Step-by-Step Guide: The Lying Leg Curl

The lying leg curl is a foundational exercise for isolating the hamstrings.

1. Setup:
   • Lie face down on the leg curl machine bench, ensuring your knees are just off the end of the pad.
   • Position the ankle pad so it rests just above your Achilles tendon, on the lower calf.
   • Adjust the machine to ensure a full range of motion without your hips lifting off the bench.
   • Grasp the handles firmly to stabilize your upper body.
2. Execution:
   • Concentric Phase (Curl): Exhale and slowly curl your legs upwards by flexing your knees, bringing your heels towards your glutes. Focus on contracting your hamstrings.
   • Peak Contraction: Squeeze your hamstrings at the top of the movement for a brief moment.
   • Eccentric Phase (Lower): Inhale and slowly extend your legs back to the starting position, resisting the weight. Control the movement throughout, avoiding a rapid drop.
3. Key Cues:
   • Mind-Muscle Connection: Actively think about squeezing your hamstrings.
   • Controlled Movement: Avoid using momentum or swinging the weight.
   • Hip Stability: Keep your hips pressed firmly into the bench; do not allow them to lift.
   • Full Range of Motion: Extend your legs almost fully at the bottom, but avoid hyperextension of the knee.

Step-by-Step Guide: The Seated Leg Curl

The seated leg curl offers a different angle of attack on the hamstrings.

1. Setup:
   • Sit upright on the machine with your back firmly against the backrest.
   • Adjust the thigh pad so it rests snugly over your upper thighs, pinning them down.
   • Position the ankle pad on your lower calves, just above the Achilles tendon.
   • Ensure your knees are aligned with the machine's pivot point.
   • Grasp the side handles for stability.
2. Execution:
   • Concentric Phase (Curl): Exhale and slowly curl your legs downwards and backward, bringing your heels towards your glutes. Focus on a strong hamstring contraction.
   • Peak Contraction: Hold the contraction briefly at the bottom.
   • Eccentric Phase (Lower): Inhale and slowly release the weight, extending your legs back to the starting position with control.
3. Key Cues:
   • Back Contact: Maintain constant contact between your back and the backrest.
   • Smooth Motion: Avoid jerking the weight.
   • Controlled Descent: The eccentric phase should be just as controlled as the concentric.

Step-by-Step Guide: The Standing Leg Curl

The standing leg curl allows for unilateral training, addressing imbalances and improving proprioception.

1. Setup:
   • Stand upright, facing the machine or cable pulley, with a slight bend in your supporting knee.
   • Place one ankle into the ankle pad or strap, ensuring it's secure.
   • Use the machine handles or a stable support for balance.
   • Ensure your working knee is aligned with the machine's pivot point (if applicable).
2. Execution:
   • Concentric Phase (Curl): Exhale and slowly curl your working leg backward and upward, bringing your heel towards your glutes. Focus on isolating the hamstring.
   • Peak Contraction: Squeeze the hamstring at the top of the movement.
   • Eccentric Phase (Lower): Inhale and slowly extend your leg back to the starting position, controlling the weight's return.
3. Key Cues:
   • Stable Torso: Keep your core engaged and avoid arching your lower back or leaning excessively.
   • Isolated Movement: Only the working leg should move; the supporting leg and torso should remain stable.
   • Controlled Descent: Resist the weight throughout the entire eccentric phase.

Common Mistakes to Avoid

To maximize effectiveness and minimize injury risk, be mindful of these common errors:

• Using Excessive Weight: This leads to momentum-driven reps, where other muscles (like the glutes or lower back) compensate, reducing hamstring isolation.
• Partial Range of Motion: Not fully extending the legs at the bottom or not achieving a strong contraction at the top limits muscle engagement and development.
• Lifting Hips/Arching Back: Often seen in lying leg curls, this indicates too much weight and reduces hamstring isolation, placing strain on the lower back.
• Rushing the Eccentric Phase: The lowering (eccentric) phase is crucial for muscle growth and strength. Dropping the weight quickly diminishes this benefit and increases injury risk.
• Lack of Mind-Muscle Connection: Simply moving the weight through space isn't enough. Focus on actively squeezing and stretching the hamstrings.

Programming and Progression

Integrate hamstring curls into your leg routine after compound movements like squats or deadlifts, or on a dedicated hamstring day.

• Rep Ranges:
  • Hypertrophy (Muscle Growth): 8-15 repetitions per set with moderate weight.
  • Strength: 6-8 repetitions per set with heavier weight (ensure perfect form).
  • Endurance: 15+ repetitions per set with lighter weight.
• Sets: Typically 3-4 sets per exercise.
• Progressive Overload: To continue making progress, gradually increase the resistance (weight), the number of repetitions, the number of sets, or the time under tension (e.g., slower eccentric phase). You can also explore advanced variations like the Nordic hamstring curl.

Benefits of Strong Hamstrings

Developing strong, balanced hamstrings through exercises like the leg curl offers significant advantages:

• Injury Prevention: Strong hamstrings are crucial for stabilizing the knee joint and preventing injuries such as ACL tears and hamstring strains, especially in athletes.
• Improved Athletic Performance: Powerful hamstrings contribute to faster sprinting speeds, higher jumps, and more explosive movements in sports.
• Enhanced Lower Body Aesthetics and Balance: Well-developed hamstrings create a balanced and aesthetically pleasing physique, complementing strong quadriceps.
• Support for Knee Joint Stability: Working in conjunction with the quadriceps, strong hamstrings help maintain overall knee health and function.

Safety Considerations and When to Consult a Professional

While leg curls are generally safe, always prioritize proper form over the amount of weight lifted.

• Listen to Your Body: Distinguish between muscle fatigue and pain. If you experience sharp or persistent pain, stop the exercise immediately.
• Pre-existing Conditions: Individuals with knee injuries, lower back pain, or other musculoskeletal issues should consult a healthcare professional or physical therapist before performing leg curls.
• Professional Guidance: If you are new to strength training or unsure about proper form, seek guidance from a certified personal trainer or kinesiologist. They can provide personalized instruction and ensure you are performing the exercises effectively and safely.