BJJ Underhook: White Belt Biomechanics Guide

1. From a kneeling or crawling position, extend your non-hooking arm towards your opponent's hip.
2. Simultaneously, insert your hooking arm *under* their armpit, palm facing your own head, fingers pointing towards their opposite side.
3. Drive your shoulder and upper chest into their torso, compressing their diaphragm.
4. Angle your hips slightly to your hooking arm's side, creating a diagonal line of force.
5. Your non-hooking arm maintains a frame on their hip or thigh, preventing them from posturing up or turning away.
6. Maintain a wide, stable base with your knees and feet on the mat, distributing your weight evenly.
7. Continuously apply upward pressure with your hooking arm and forward pressure with your chest.

• Error: Reaching too far with the hooking arm and extending the elbow fully.
• Injury: Ulnar collateral ligament (elbow) sprain due to hyperextension when opponent applies pressure or attempts to straighten your arm.
• Fix: Keep a slight bend in the elbow and drive the shoulder into the opponent's torso, maintaining a strong frame.
• Error: Letting the non-hooking arm go slack or losing contact with the opponent's hip.
• Injury: Loss of balance and control, leading to the opponent easily posturing up or passing your guard, potentially causing a hyperextended knee if you fall backward awkwardly.
• Fix: Actively frame the hip with the non-hooking arm, maintaining contact and using it to control distance and hip angle.
• Error: Arching the back excessively instead of driving with the hips and shoulders.
• Injury: Lumbar strain or disc compression due to improper spinal alignment under pressure.
• Fix: Focus on driving the shoulder into the opponent and using hip rotation to create leverage, keeping the spine neutral.

1. Solo Drill: Practice the arm insertion and shoulder drive motion without a partner, focusing on hip angle and chest pressure. (50 reps)
2. Partner Drill (Static): Partner kneels. You insert the underhook and drive, holding for 5 seconds. Repeat on both sides. (10 reps per side)
3. Partner Drill (Light Resistance): Partner lightly resists the underhook insertion. Focus on maintaining the frame and driving through. (25% resistance, 10 reps per side)
4. Transition Drill: Start in a neutral position (e.g., hands around opponent's waist), practice securing the underhook as they attempt to create space. (50% resistance, 5 reps per side)
5. Positional Sparring (Guard Retention): Focus on securing and maintaining the underhook from closed guard or half guard while your partner attempts to pass. (75% resistance, 2-minute rounds)
6. Live Rolling: Integrate underhook attempts naturally into your rolling, focusing on establishing and exploiting the position. (100% resistance, 3-minute rounds)

• WHEN TO ATTEMPT:
• When your opponent attempts a guard pass and their weight is forward.
• When you are on your knees trying to establish guard from a bad position.
• When you are in a scramble and need to regain control or prevent a takedown.
• PRIMARY COUNTERS:
• Opponent's Underhook: If your opponent secures an underhook, immediately counter by driving your shoulder into their face or chest, creating space to either secure your own underhook or retreat to a safer position. Maintain a strong frame with your free arm.
• Framing and Hip Escape: If your opponent has an underhook and is driving into you, use your free arm to frame against their hip or thigh. Simultaneously, perform a hip escape away from the direction of their pressure to create space and disrupt their leverage.
• Whizzer (Overhook): If your opponent has an underhook, secure an overhook on their arm (called a whizzer) and drive your shoulder into their chest. This negates their leverage and allows you to potentially turn into them or create an opportunity to escape.

Watch step-by-step breakdowns from black belt instructors: