Bicep Curls: Why You Shouldn't Lock Your Elbows, Risks, and Optimal Technique

Should you lock your elbows when doing bicep curls?

No, you should generally avoid "locking" or hyperextending your elbows at the bottom of a bicep curl. Instead, aim for a controlled, full range of motion that leaves a slight bend in the elbow to protect the joint and maintain constant tension on the biceps muscle.

Understanding the Bicep Curl

The bicep curl is a foundational resistance exercise designed to target the biceps brachii, brachialis, and brachioradialis muscles of the upper arm. Its primary action is elbow flexion, where the forearm moves towards the shoulder. Proper execution emphasizes controlled movement through the full available range of motion (ROM) to maximize muscle activation and hypertrophy while minimizing injury risk.

The Biomechanics of Elbow Extension

The elbow joint is a hinge joint, primarily allowing flexion and extension. When performing a bicep curl, the eccentric (lowering) phase involves elbow extension.

• Anatomy Involved: The elbow joint comprises the humerus (upper arm bone), ulna, and radius (forearm bones). It is stabilized by a complex network of ligaments, including the ulnar collateral ligament (UCL) and radial collateral ligament (RCL), which prevent excessive sideways movement, and the joint capsule itself.
• Forces at Play: As you lower the weight, gravity and the momentum of the dumbbell or barbell pull the forearm downwards. If you allow the elbow to snap into full extension or hyperextension, these forces can place significant stress on the joint structures, particularly the ligaments and articular cartilage.

The Risks of "Locking" Your Elbows

"Locking" your elbows refers to extending them beyond their natural range of motion or allowing them to forcefully snap straight at the bottom of the movement. This practice carries several potential risks:

• Joint Hyperextension: For individuals with hypermobile joints, locking can lead to hyperextension, where the elbow extends beyond 180 degrees. This can strain the joint capsule and ligaments, potentially leading to instability or acute injury. Even for those without hypermobility, forceful extension can still cause undue stress.
• Ligament Strain and Damage: The ligaments around the elbow, especially the UCL (critical for throwing athletes), can be stretched or torn under repetitive or forceful hyperextension. This can lead to pain, instability, and long-term joint issues.
• Nerve Impingement: The ulnar nerve, often called the "funny bone" nerve, passes through a tunnel on the inside of the elbow (cubital tunnel). Forceful or repetitive locking can compress or stretch this nerve, leading to symptoms like numbness, tingling, or weakness in the hand and fingers.
• Reduced Muscle Tension: When you fully lock your elbows, the weight is often supported by the skeletal structure of the joint rather than the active tension in the biceps muscle. This momentarily offloads the muscle, reducing the "time under tension" – a key factor for muscle growth. It essentially provides a brief rest period that detracts from the exercise's effectiveness.
• Increased Joint Wear and Tear: Repeated impact from locking can contribute to the degradation of articular cartilage over time, potentially increasing the risk of osteoarthritis.

The Benefits of Controlled Extension

While locking is detrimental, a controlled, near-full extension is crucial for maximizing muscle development and joint health.

• Full Range of Motion (ROM): Extending the elbow to a point just before locking allows the biceps muscle to achieve its maximum stretched position. This full eccentric stretch is vital for stimulating muscle growth (hypertrophy) and improving flexibility within the muscle belly.
• Maintaining Muscle Tension: By stopping just short of a lock, you keep continuous tension on the biceps throughout the entire set. This increases the total time the muscle is under load, which is a powerful stimulus for muscle adaptation.
• Joint Health Preservation: A controlled eccentric phase, where you actively resist the weight as you lower it, engages the muscles around the joint, providing dynamic stability. This active control protects the passive structures (ligaments, cartilage) from excessive strain.
• Improved Proprioception: Consciously controlling the movement through its full, safe range enhances proprioception – your body's awareness of its position in space. This improves motor control and can translate to better performance in other lifts and daily activities.

Optimal Elbow Position During Bicep Curls

The ideal technique for bicep curls involves a controlled movement pattern that prioritizes muscle engagement and joint safety.

• The "Soft Lock" or Slight Bend: At the bottom of the eccentric phase, aim to extend your elbows almost completely straight, but always maintain a very slight bend. This "soft lock" ensures the biceps are fully lengthened without putting undue stress on the elbow joint. You should feel the stretch in your biceps, not a jolt in your elbow.
• Controlled Eccentric Phase: Do not let gravity do all the work. Actively resist the weight as you lower it, taking 2-3 seconds to reach the bottom position. This maximizes the benefits of the eccentric contraction.
• Avoiding Momentum: Focus on using your biceps to lift and lower the weight, rather than swinging your body or using momentum. Excessive momentum often leads to uncontrolled movements, including forceful elbow extension.

Practical Application and Coaching Cues

For both lifters and trainers, here are actionable tips:

• For Lifters:
  • "Control the Negative": Consciously slow down the lowering phase of the curl.
  • "Stop Before the Snap": Feel for the point just before your elbow would fully straighten and stop there.
  • "Maintain Tension": Imagine you're always pulling the weight, even as you lower it.
  • Use Mirrors: Observe your elbow position to ensure you're not locking out.
• For Trainers:
  • Verbal Cues: Use phrases like "soft elbows," "slight bend at the bottom," or "don't let your elbows lock out."
  • Tactile Cues: Gently place a hand near the client's elbow to guide their range of motion, if appropriate and with consent.
  • Demonstrate: Show both the incorrect (locking) and correct (soft lock) technique clearly.
  • Regress if Necessary: If a client struggles with control, reduce the weight or use an exercise variation that inherently limits the risk of locking (e.g., preacher curls, which fix the upper arm position).

Conclusion: Prioritizing Safety and Effectiveness

When performing bicep curls, the goal is to maximize tension on the biceps while safeguarding your joints. While a full range of motion is crucial for optimal muscle development, this does not equate to forcefully locking your elbows. By maintaining a slight, controlled bend at the bottom of the movement, you protect your elbow joint from potential injury, ensure continuous muscle engagement, and ultimately achieve a more effective and sustainable training outcome. Always prioritize proper form over lifting heavier weight.