The cable skull crusher is a triceps isolation exercise performed lying on a bench with a rope attachment pulled from a low cable pulley behind the head. Unlike the free-weight version, the cable provides constant tension throughout the range of motion, keeping the triceps under load even at the top of the rep. It targets all three heads of the triceps and is commonly used as an accessory movement to build arm size and lockout strength for pressing exercises.
Muscles Targeted
- Primary: Triceps brachii (all three heads)
- Secondary: Anconeus
- Tertiary: Forearm and shoulder stabilizers (holding the upper arms fixed)
Starting Position
Position a flat bench with the head end facing a low cable pulley fitted with a rope attachment. Lie back on the bench with your head near the end closest to the machine, reach back overhead and grasp the rope with both hands, palms facing each other. Extend your arms toward the ceiling so the cable stays taut, elbows pointed upward and slightly bent.
Execution Steps
- Fix your upper arms perpendicular to the floor and keep them stationary for the entire set
- Bend your elbows to lower the rope behind your head toward your forehead, hinging only at the elbow joint
- Continue lowering until you feel a deep stretch in your triceps with your elbows fully flexed
- Pause briefly at the bottom of the stretch without letting your upper arms drift
- Extend your elbows to press the rope back to the starting overhead position, squeezing the triceps at the top
- Repeat for the desired reps, keeping the movement isolated to the elbow joint throughout
Form Cues
- Keep your elbows pointed toward the ceiling and close together, not flared out to the sides
- Anchor your upper arms in place - only your forearms should move
- Move through a full range of motion, from a deep stretch to full lockout
- Keep your core and lower back braced against the bench to avoid arching
- Control the eccentric (lowering) portion rather than letting the cable pull your arms back quickly
Common Mistakes
- Flaring the elbows outward: reduces triceps isolation and adds shoulder strain; keep elbows tracking directly overhead.
- Positioning the bench at the wrong distance from the pulley: changes the resistance curve and slackens the cable; adjust so tension stays constant with a slight stretch at the top.
- Moving the upper arms during the rep: turns the isolation movement into more of a pulldown; anchor the upper arms and hinge only at the elbow.
- Using excessive weight: forces reliance on shoulder momentum instead of triceps strength; choose a weight that allows full control.
- Cutting the range of motion short: reduces the stretch and limits triceps recruitment; lower the rope until the upper arms are fully flexed.
Variations
- Lying barbell or EZ-bar skull crusher: free-weight version without constant cable tension, useful for progressive overload
- Standing or kneeling cable overhead triceps extension: alternate cable setup emphasizing the long head from an upright position
- Single-arm cable skull crusher: unilateral version that addresses strength imbalances between arms
- Cable rope pushdown: complementary triceps isolation exercise performed from a standing position
- Decline bench cable skull crusher: increases stretch and range of motion on the long head of the triceps
Tips for Progression
- Increase weight in small increments once 12-15 reps are completed with full control
- Add a 1-2 second pause at full stretch to increase time under tension
- Progress from a two-arm to a single-arm variation to further challenge stability
- Slow the eccentric phase to 3-4 seconds to increase muscle stimulus and growth
Training Notes
Include cable skull crushers as a triceps isolation finisher 1-2 times per week, after compound pressing movements such as the bench press or overhead press. Use 3-4 sets of 10-15 reps with 60-90 seconds of rest between sets. Because the cable maintains tension through the full range of motion, it works well as a pump-focused finisher at the end of an arm or push session.