The Hook Grip - Mark Rippetoe
Olympic weightlifters use a grip technique that provides enough grip security to hold on to highly-accelerated loads on the barbell. The "hook grip" is useful for general strength training as well, for several reasons.
1. A hook grip is performed by taking a regular double-overhand grip on the bar, and then moving the thumb in toward the opposing fingertips and placing the distal digit of the middle finger on top of the thumbnail, with the other fingers accommodating this position. This doesn't work with a fat bar or short fingers, but for most people and most equipment commonly found in the weight room it can solve a lot of problems.
With a chalked hand, this middle finger/thumbnail interface creates both friction between the two surfaces and quite a bit of pressure as the thumb is pulled up into the knurl of the bar. The pressure on the skin of the thumb can be mitigated by athletic tape, but it still takes some getting used to. When you first decide to use it, you'll need to hook all your warmups for several workouts until your thumbs can tolerate the load. They can: Brad Gillingham has pulled 881 with a hook grip.
2. The mechanism by which a normal double-overhand grip works relies on "squeeze", as the fingers encircle the bar and apply pressure around the circumference. Both forearm flexors and extensors are actively involved in this contraction, and since some of these muscles cross the elbow joint, tight forearms also tighten the elbows. This prevents the rapid rotation required for racking a snatch or a clean, since a tight elbow can't rotate as fast as a loose elbow. And since we power clean and power snatch in strength training, the hook grip is useful. And it helps a novice lifter learn how to keep the elbows straight, since the bar can hang securely from loose elbows.
3. It's also useful for maintaining the rotational symmetry of the shoulders in a heavy pull. An alternate grip – commonly seen as the default deadlift grip for people who don't even need to use it because the weight isn't heavy – features one shoulder in internal rotation and one shoulder in external rotation, since one hand is prone and the other supine. This almost always produces a rotation about the saggital plane as the bar gets pushed away from the supine side (through some mechanism we haven't entirely explained). It's sometimes hard to control, and it can get you hurt if the bar gets too far away from you. A hook grip places both shoulders in nice symmetrical internal rotation, simplifying the mechanics of the pull by eliminating the rotation.
4. A minor beneficial side-effect is the tendency for the bar to ride a tiny bit lower in the hands in a hook grip than in an alternate grip, because most people tend to "overgrip" the bar when they alternate their prone/supine hands. A lower bar position in the grip reduces the ROM of the deadlift by that distance, and every little bit helps in a meet.
5. And a major beneficial side effect is safety: distal and proximal bicep tendon avulsions have increased in the public awareness (if not frequency) lately. They are the direct result of the load on the supine side of the grip, where the humerus is externally rotated and the bicep is flexed. They always require surgical repair. Since the hook grip preserves the internal rotation symmetry for both shoulders, there is no supine side to avulse.
The hook grip should not be considered an advanced Olympic weightlifting technique. It should be learned the first time you clean, and used for heavy deadlifts when it is appropriate. It's usually appropriate.