Cable Concentration Extension (on knee) exercise animation (Male)

Cable Concentration Extension (on knee)

Target muscle
Triceps Brachii
Equipment
Cable
Body part
Upper Arms
Type
Strength

The cable concentration extension (on knee) is a single-arm isolation exercise that targets the triceps brachii. Kneeling and bracing your working arm against your thigh removes momentum, so the cable keeps constant tension on the triceps through the full range. It's a good finisher for building arm strength and definition with strict, controlled reps.

How to do the Cable Concentration Extension (on knee)

  1. 1Set a cable pulley to the low position and attach a single-grip handle.
  2. 2Kneel on one knee facing the machine, with the same-side foot or knee forward for a stable base.
  3. 3Grab the handle with the working arm and brace the back of your upper arm against the top of your thigh so your elbow stays fixed.
  4. 4Start with your elbow bent and the handle near your shoulder, keeping your wrist neutral and your torso still.
  5. 5Extend your elbow to press the handle down and away until your arm is fully straight, squeezing the triceps at the bottom.
  6. 6Pause briefly at full extension without locking out aggressively.
  7. 7Lower the handle under control back to the start, resisting the cable the whole way.
  8. 8Finish your reps, then switch sides and repeat with the other arm.

Form tips

  • Keep your upper arm pinned to your thigh so only your forearm moves and the triceps does the work.
  • Use a slow, controlled negative on the way back up to maximize tension on the muscle.
  • Keep your wrist neutral and firm so the load stays on the triceps rather than your grip.
  • Pick a weight you can fully straighten with strict form, since this is an isolation, not a strength, lift.
  • Brace your core and keep your torso upright to stop your body from swinging into the rep.

Common mistakes

  • Letting the elbow drift off the thigh, which turns the movement into a swing and takes tension off the triceps.
  • Using momentum or leaning your torso to throw the handle down, which cheats the rep and reduces muscle work.
  • Stopping short of full extension, which skips the part of the range where the triceps contracts hardest.
  • Loading too heavy, which forces you to flare the elbow and round the wrist, raising joint strain.
  • Yanking the handle back up instead of resisting it, wasting the eccentric portion of every rep.

Frequently asked questions

What muscles does the cable concentration extension work?

It isolates the triceps brachii, the muscle on the back of the upper arm responsible for straightening the elbow. Bracing your arm against your thigh keeps the focus on the triceps with little help from other muscles.

Why use a cable instead of a dumbbell for concentration extensions?

The cable keeps constant tension on the triceps through the whole range, including the top, where a dumbbell's resistance drops off. This makes the cable version more effective for steady muscle tension.

How many sets and reps should I do?

As an isolation finisher, 3 to 4 sets of 10 to 15 reps per arm works well. Use a controlled weight you can fully extend with strict form rather than chasing heavy loads.

Is the cable concentration extension good for beginners?

Yes. Bracing your arm on your thigh fixes the elbow and removes momentum, making it easy to learn proper triceps form before progressing to heavier pressing movements.

Where should I feel this exercise?

You should feel it in the triceps on the back of your working upper arm, especially as you fully straighten the elbow. If you feel it mainly in your shoulder or grip, lighten the load and pin your upper arm to your thigh.

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