Supine Barbell French Curl

The supine barbell French curl, widely known as the skull crusher or lying triceps extension, is a lying isolation exercise performed with a barbell that builds size and strength in the triceps brachii. Lying on a flat bench keeps the shoulders fixed, so nearly all the work happens at the elbow joint, making it one of the most direct triceps isolation movements available. It is a staple accessory lift for pressing strength and arm development.

Muscles Targeted

• Primary: Triceps brachii (all three heads, with emphasis on the long head)
• Secondary: Anconeus
• Tertiary: Wrist flexors and forearm stabilizers (grip)

Starting Position

Lie flat on a bench with your feet planted firmly on the floor for stability. Hold a barbell with a shoulder-width, overhand (pronated) grip and press it to arm's length above your chest, directly over your shoulders. Tuck your elbows in so they point toward the ceiling rather than flaring out, and keep your upper arms nearly vertical throughout the set.

Execution Steps

1. Brace your core and fix your upper arms in place, perpendicular to the floor, before initiating the movement
2. Bend only at the elbows, lowering the barbell in a controlled arc toward your forehead or just behind your head
3. Keep your upper arms stationary as the bar descends - only the forearms should move
4. Lower until your forearms are roughly parallel to the floor or you feel a deep stretch in the triceps
5. Reverse the motion by extending your elbows and pressing the bar back to the starting position
6. Lock out fully but without slamming the elbows, then repeat for the desired number of reps

Form Cues

• Keep elbows tucked and stationary: Flaring elbows outward shifts stress to the shoulders and reduces triceps isolation
• Lower to the forehead or behind the head, not the throat: Track the bar path carefully to avoid striking your face
• Use a slight bend at the bottom: Locking the elbows completely at the top is fine, but keep tension on the triceps rather than resting the weight on the joint
• Control the descent: A slow, deliberate lowering phase increases time under tension and protects the elbows
• Keep your feet flat and core tight to prevent the lower back from arching off the bench

Common Mistakes

• Flaring the elbows out: This turns the movement into a partial press and takes tension off the triceps - keep upper arms fixed and vertical.
• Using too much weight: Excess load forces the elbows to drift and increases strain on the elbow joints; use a weight that allows full control.
• Bouncing the bar off the forehead: This is a serious safety risk and reduces muscle tension; always control the bottom position.
• Moving the upper arms: Letting the shoulders travel forward or back turns this into a pressing movement rather than an isolation exercise.
• Arching the lower back: Overarching to move more weight strains the spine; keep the lower back flat against the bench.

Variations

• E-Z bar French curl: The angled grip reduces wrist strain and is easier on the joints for most lifters
• Dumbbell French curl: Allows each arm to move independently and through a slightly greater range of motion
• Incline French curl: Performed on an incline bench to increase stretch on the long head of the triceps
• Cable overhead triceps extension: Provides constant tension and a different resistance curve than free weights
• Single-arm French curl: Isolates one side at a time to correct strength imbalances

Tips for Progression

• Increase weight in small increments (2.5-5 pounds per side) once you can complete all sets with strict elbow position
• Add reps before adding load, progressing toward 12-15 reps before increasing weight
• Slow the eccentric to 3-4 seconds to increase time under tension without adding weight
• Switch to a heavier compound triceps movement, such as close-grip bench press, once this exercise becomes too easy for isolation work

Training Notes

Program the supine barbell French curl 1-2 times per week as an accessory movement after compound pressing exercises like bench press or overhead press. It responds well to 8-12 reps for 3 sets with 60-90 seconds of rest between sets. Because it places significant stress on the elbows, use strict form and avoid training it to failure on consecutive sessions.