Learn the BJJ half guard: leg position, knee shield, underhook and defensive mistakes. With numbers from competition analysis and clear beginner milestones.
The half guard is the position in which you trap one of your partner's legs between your own and so stop him reaching side control or north-south. The IBJJF rulebook defines it exactly this way: you lie on your back or side, have one of the top opponent's legs trapped, and thereby block his path to side control [1].
The honest answer: half guard is where beginners most often get stuck. You are neither in the safe closed guard nor moving freely, and your partner wants to flatten you. Expect a few weeks until you feel the difference between "surviving" and "playing". That is a practical estimate, not a study.
What is measurable: in a competition analysis of half-guard situations, top players mostly passed to their left, against the direction of the entangled leg. Passes toward the less common direction scored in 36.7% of cases, versus 19.7% for the more common direction [2]. For you that means: whoever is predictable gets read. And the numbers come from a video analysis of competitions, not a training experiment. Take them as a hint, not a law.
Clamp one of your partner's legs between your legs, with a foot hook behind his thigh. Goal: he must not reach side control. Milestone: you hold the trapped leg for 20 seconds even when your partner works.
Slide the upper knee between you so he cannot come flat onto your chest. That knee is your shield (also called Z-guard). With knee and forearm you keep distance. Milestone: your partner needs more than 5 seconds to get past your knee.
An arm under your partner's arm (underhook) stops him from flattening you and opens sweeps. It is the most important tool of the half guard. Milestone: you get the underhook in 5 of 10 starts against light resistance.
From the underhook you come to your side and from there to sitting. A sweep earns 2 points under IBJJF rules if you hold the top position for 3 seconds [1]. Even a simple rise is a win because it takes you out of the flat defence.
The analysis suggests the less common side had the advantage [2]. Whoever always plays the same side becomes readable. Practise half guard left and right so your partner does not know where you are going.
In half guard one of your partner's legs sits between yours, and during the pass knees and hips twist. The knee is the most frequently injured region in BJJ: in a survey of 1,140 athletes, 27.1% of injuries involved the knee, most often meniscus, anterior cruciate ligament and medial collateral ligament [3]. A systematic review names knee, chest and rib areas and the shoulder as the most frequent regions [4]. Do not let your leg be twisted against the joint, tap early at knee pain and give your partner time to release. This does not replace supervised training.
When you have the underhook, go higher at once: shoulders off the mat, hips away from your partner. Whoever stays under the arm stays down. Practise it as a chain: knee shield, underhook, rise. Three small steps are easier to learn than one big sweep. Keep a small training log: which side suited you, when did the underhook come, where did your partner flatten you? An underhook without movement is only a grip, with movement it is a plan. And one everyday tip: also play half guard without the ambition to score, just to feel how your partner reacts. Curiosity teaches you more than doggedness.
You lie on your back or side and trap one of your partner's legs between yours. That stops him reaching side control or north-south [1].
A knee that you slide between you and your partner so he cannot come flat onto your chest. It keeps distance and gives you time to get the underhook.
A sweep earns 2 points if you hold the top position for 3 seconds [1]. If the half guard is passed, the opponent gets 3 points for side control or north-south [1].
Usually the underhook or the knee shield is missing. Whoever lies flat on his back has few options. Go onto your side and get the underhook.
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