Standard Arm-Bar

Taekwon-Do defence techniques are often divided into three categories: attacks, releases and breaks. The arm-bar resides under the last category as it is possible to break the elbow-joint with this technique. The arm-bar is a fundamental technique in many martial arts and is usually the first technique learned in Aikido (ikkyo) and Hapkido (kal nokki). As far as I know, we do not have a special name for this technique in Taekwon-Do; we generally just refer to it as an elbow break or adopt the common arm-bar term.

There are numerous set-ups for the arm-bar. I personally prefer to introduce Taekwon-Do students to the arm-bar as a follow up from a palm hooking block. 

The hooking block is one of the first "soft" techniques that the Taekwon-Do student learns and is an excellent set-up for a variety techniques like breaks (commonly known as joint locks or bars) and throws. We usually learn this technique the first time at Green Belt Blue Stripe level. Coincidentally this is also around the time when One Step Sparring is often introduced and such "break" techniques become more feasible. Most people do the palm hooking block too low on the arm. Trying to block your opponent's fast approaching wrist is quite difficult. It is better to block higher up the arm, preferably the upper arm. The palm hooking block moves in a circular motion wiping the attacking arm out of the way and ending with the palm resting on the attacker's attacking arm.

From here the palm swiftly slides down the attacker's arm towards the wrist where it tightens around the wrist and is then officially known as a grasping block. 

To secure the grasping block you will tighten and turn your grip from the little finger. Also lift up your forearm against the attacker's arm. In so doing you effectively clamp down on the attacker's arm with pressure from your hand above and pressure from your arm below. This creates an extremely strong hold.

To set-up the arm-bar you will quickly move in closer and press your arm behind (above) the elbow joint and start to rotate it over the arm. You can either use your forearm or your elbow to put pressure on your opponent's arm.

Finally press directly down onto the arm just behind the elbow joint. It is usually more effective if you drop your body weight (sine wave motion) into the technique. You can do this by moving into a lower stance. For instance, you can change from a rear foot stance or an L-stance into a fixed stance or walking stance.

Done with moderate force, this is an effective control technique. Done hard and fast, you can easily overextend the elbow joint and probably break it, so be careful while training not to injure your training partner.