The single arm cross body tricep extension is a one-dumbbell isolation exercise performed lying on a flat bench, lowering the weight toward the opposite shoulder to train thetriceps. Unlike a two-hand skull crusher, the forearm travels diagonally across the chest, so the elbow points at the ceiling with the upper arm angled slightly inward and the lateral head takes more of the work than a straight overhead line gives it. The free hand can spot the working elbow, which keeps it still. Lifters program it as an arm-day accessory after pressing.
What Muscles Does the Single Arm Cross Body Tricep Extension Work?
- Primary: Triceps brachii (lateral and long heads)
- Secondary: Anconeus
- Tertiary: Anterior deltoid, pectoralis major, forearm flexors (grip)
How Do You Set Up for the Single Arm Cross Body Tricep Extension?
Pick up one dumbbell and lie back on a flat bench, feet flat on the floor, hips and shoulder blades pressed into the pad. Press the dumbbell to arm's length above your shoulder with a neutral grip, thumb pointing toward your face. Angle the upper arm slightly toward your midline so the elbow points at the ceiling, and cup your free hand around the working elbow.
How Do You Perform the Single Arm Cross Body Tricep Extension?
- Lock the upper arm vertical with the elbow pointing up and the dumbbell stacked over your shoulder.
- Bend the elbow slowly, lowering the dumbbell diagonally across your chest toward the opposite shoulder.
- Stop when the dumbbell hovers an inch above the front of the opposite shoulder and the forearm rests across your chest.
- Pause for one count at the bottom with the upper arm still vertical and the elbow unmoved.
- Straighten the elbow along the same diagonal, pressing the dumbbell back up until the arm is fully extended.
- Squeeze the triceps for a count at lockout, then re-stack the dumbbell over the shoulder for the next rep.
What Are the Key Form Cues?
- Elbow stays a fixed point: Feel the free hand holding the elbow still while only the forearm hinges through the whole rep.
- Draw a diagonal: Aim the dumbbell at the opposite collarbone on the way down, never straight at your face.
- Keep the wrist neutral and the thumb pointing back so the dumbbell does not roll onto the forearm at the bottom.
- Press your shoulder blades into the bench so the working shoulder does not lift as the elbow straightens.
- Feel the stretch across the back of the arm before you reverse at the bottom.
What Are the Most Common Mistakes?
- Grabbing a dumbbell you press rather than extend: the upper arm swings toward the hip and the shoulder lifts the load, so drop 5 pounds until the elbow stays vertical.
- Letting the elbow drift outward: the forearm drops straight down and the lift becomes a half skull crusher, so guide the elbow inward with your free hand.
- Lowering onto the shoulder and resting: the triceps unload at the bottom and momentum starts the next rep, so stop an inch above the shoulder and pause.
- Rotating the palm forward at the bottom: the wrist bends under the load and the forearm flexors tire before the triceps, so keep the grip neutral.
- Lifting the head to watch the dumbbell: the neck flexes and the upper back peels off the bench, so keep the head down.
What Are the Best Single Arm Cross Body Tricep Extension Variations?
- Floor cross body tricep extension: the floor limits the bottom range, for lifters learning the path.
- Incline cross body tricep extension: a 30-degree bench sets the arm further overhead and stretches the long head.
- Cross body tricep extension with a twist: rotating the palm inward at the bottom shifts work toward the medial head.
- Alternating cross body extension: both dumbbells up, one arm working at a time.
- Cross Body Triceps Extensions with Resistance Bands: the same diagonal line standing with a band anchored high.
How Do You Progress the Single Arm Cross Body Tricep Extension?
- Add 5 pounds to the dumbbell once you finish every set at the top of the rep range with the elbow still vertical.
- Work from 10 to 15 reps per arm at a fixed weight before jumping.
- Add a fourth set per arm when three sets no longer leave the triceps fatigued.
- Lower for a three-count and hold the bottom stretch for two counts when the next dumbbell is too heavy.
How Should You Program the Single Arm Cross Body Tricep Extension?
Place the single arm cross body tricep extension late in an arm or push session, after bench pressing and any dips. Train it 1 to 2 times per week for 3 to 4 sets of 10 to 15 reps per arm, resting 45 to 60 seconds between arms rather than between full sets. Pair it with a rope pushdown or an overhead extension so the medial and long heads also get direct work.
