Bicep Leg Curl: Clarifying the Misconception, Anatomy, and Proper Execution of Leg and Bicep Curls

How to do a bicep leg curl?

The term "bicep leg curl" is a common misunderstanding of anatomical terminology; the biceps muscles are located in the arm, while leg curls primarily target the hamstrings in the back of the thigh. This article clarifies the correct muscles involved in a leg curl and provides instructions for both hamstring-focused leg curls and arm-focused bicep curls.

Understanding the Terminology: Biceps vs. Hamstrings

The human body's muscular system is precise, and accurate terminology is crucial for effective and safe training. The confusion around "bicep leg curl" likely stems from a conflation of two distinct muscle groups:

• Biceps Brachii: Located on the front of the upper arm, primarily responsible for elbow flexion (bending the arm) and forearm supination (rotating the palm upwards).
• Hamstrings: A group of three muscles on the back of the thigh—the semitendinosus, semimembranosus, and biceps femoris. Their primary actions are knee flexion (bending the leg) and hip extension (moving the leg backward).

While one of the hamstring muscles is indeed called the biceps femoris, it is critical to understand that it is part of the leg's posterior chain, not the arm. Therefore, an exercise targeting the arm's biceps would be a "bicep curl," and an exercise targeting the leg's hamstrings would be a "leg curl."

The Biceps Brachii: Anatomy and Function

The biceps brachii is a two-headed muscle situated on the anterior (front) compartment of the upper arm.

• Origin: The "short head" originates from the coracoid process of the scapula, and the "long head" originates from the supraglenoid tubercle of the scapula.
• Insertion: Both heads insert onto the radial tuberosity of the radius bone in the forearm.
• Primary Actions:
  • Elbow Flexion: Bending the elbow, bringing the forearm towards the upper arm (e.g., lifting a weight).
  • Forearm Supination: Rotating the forearm so the palm faces upwards (e.g., turning a doorknob).
  • It also assists slightly in shoulder flexion.

Exercises targeting the biceps brachii include various forms of bicep curls (dumbbell, barbell, hammer, preacher curls).

The Hamstrings: Anatomy and Function (and the Biceps Femoris)

The hamstrings are a powerful group of three muscles that run down the back of the thigh, forming the posterior boundary of the popliteal fossa (the hollow behind the knee).

• Semitendinosus: Medial (inner) hamstring.

• Semimembranosus: Lies deep to the semitendinosus, also medial.

• Biceps Femoris: The lateral (outer) hamstring, with a long head and a short head. This is where the "bicep" part of the confusion often arises.

• Origin: All three muscles (long head of biceps femoris, semitendinosus, semimembranosus) originate from the ischial tuberosity (the "sit bone") of the pelvis. The short head of the biceps femoris originates from the linea aspera of the femur.

• Insertion: They insert onto various points around the tibia and fibula bones of the lower leg.

• Primary Actions:

  • Knee Flexion: Bending the knee (e.g., the "curl" action in a leg curl).
  • Hip Extension: Moving the leg backward at the hip (e.g., the action in a Romanian deadlift or glute-ham raise).

Exercises targeting the hamstrings include leg curls (lying, seated, standing), Romanian deadlifts, good mornings, and glute-ham raises.

Performing a Leg Curl (Targeting Hamstrings)

The leg curl is an isolation exercise designed to strengthen the hamstrings by focusing on knee flexion. It can be performed on various machines:

Seated Leg Curl

1. Setup: Sit on the machine with your back firmly against the pad. Adjust the lower leg pad so it rests just above your ankles (on your Achilles tendon). Adjust the thigh pad to secure your thighs against the seat.
2. Execution: Grasp the handles for stability. Exhale and slowly curl your heels towards your glutes, contracting your hamstrings.
3. Peak Contraction: Hold the contraction briefly at the peak, squeezing the hamstrings.
4. Controlled Release: Inhale and slowly extend your legs back to the starting position, controlling the weight through the eccentric (lowering) phase. Avoid letting the weight "snap" back.
5. Repetitions: Perform for your desired number of repetitions.

Lying Leg Curl

1. Setup: Lie face down on the machine. Position your knees just off the edge of the bench, ensuring your hamstrings are fully engaged. Place your lower legs under the pad, with the pad resting just above your ankles.
2. Execution: Grasp the handles for stability. Exhale and slowly curl your heels towards your glutes, contracting your hamstrings.
3. Peak Contraction: Hold the contraction briefly, focusing on the squeeze in your hamstrings.
4. Controlled Release: Inhale and slowly extend your legs back to the starting position, maintaining tension and avoiding a rapid drop of the weight.
5. Repetitions: Perform for your desired number of repetitions.

Performing a Bicep Curl (Targeting Biceps Brachii)

The bicep curl is a fundamental exercise for developing the biceps brachii. It can be done with dumbbells, barbells, or cables.

Dumbbell Bicep Curl (Standing)

1. Setup: Stand upright with a dumbbell in each hand, palms facing forward (supinated grip). Keep your elbows close to your torso.
2. Execution: Exhale and, keeping your upper arms stationary, curl the dumbbells upwards by contracting your biceps. Continue until your biceps are fully contracted and the dumbbells are at shoulder level.
3. Peak Contraction: Squeeze your biceps at the top of the movement for a brief moment.
4. Controlled Release: Inhale and slowly lower the dumbbells back to the starting position, fully extending your arms and controlling the weight throughout the eccentric phase.
5. Repetitions: Perform for your desired number of repetitions.

Barbell Bicep Curl (Standing)

1. Setup: Stand upright with a barbell in your hands, palms facing forward (underhand grip), hands shoulder-width apart. Keep your elbows close to your torso.
2. Execution: Exhale and, keeping your upper arms stationary, curl the barbell upwards by contracting your biceps. Continue until your biceps are fully contracted and the barbell is at shoulder level.
3. Peak Contraction: Squeeze your biceps at the top.
4. Controlled Release: Inhale and slowly lower the barbell back to the starting position, fully extending your arms and controlling the weight.
5. Repetitions: Perform for your desired number of repetitions.

Common Misconceptions and Clarifications

The term "bicep leg curl" highlights a common area of confusion in fitness: the precise naming and function of muscles.

• Muscle Naming: Many muscles have "bi" or "tri" in their names (e.g., biceps brachii, triceps brachii, biceps femoris) indicating the number of heads or origins they have. This doesn't mean they perform the same function or are located in the same body region.
• Exercise Naming: Exercises are generally named after the primary joint action they facilitate and/or the muscle group they target. A "curl" implies a bending action, typically at the elbow or knee.
• Focus on Function: When designing a workout, focus on the function of the muscle you wish to train. If you want to strengthen the back of your thighs, you perform a leg curl (hamstrings). If you want to strengthen the front of your upper arms, you perform a bicep curl (biceps brachii).

Safety and Effective Training Principles

Regardless of the exercise, adhering to fundamental training principles is paramount for safety and efficacy.

• Proper Form Over Weight: Always prioritize correct technique over lifting heavy weight. Poor form increases injury risk and reduces muscle activation.
• Controlled Movements: Avoid using momentum. Lift and lower the weight in a controlled manner, focusing on the muscle contraction.
• Full Range of Motion: Aim for a full range of motion appropriate for the exercise to maximize muscle engagement and flexibility.
• Progressive Overload: To continue making progress, gradually increase the resistance, repetitions, sets, or decrease rest time over time.
• Listen to Your Body: Pay attention to pain signals. Sharp pain indicates something is wrong; stop the exercise immediately.
• Warm-up and Cool-down: Always begin with a dynamic warm-up and conclude with a static cool-down to prepare your body and aid recovery.
• Professional Guidance: If you are unsure about proper form or exercise selection, consult with a qualified personal trainer or exercise physiologist. They can provide personalized instruction and ensure your program aligns with your goals and physical capabilities.