The hook grip is important because it helps keep the bar in an active hold and not slip into the fingertips. The thumb helps keep the bar locked in place during the huge acceleration that is generated into the barbell.
The hook grip is usually painful and awkward for the first couple of weeks but the body should adapt the new grip. After a while you won’t even notice that your holding the bar in hook grip because it will be a naturally occuring movement.
The hook grip is utilized for all lifted below the shoulders. On overhead movements it is recommended to not use the hook grip because it can restrict the movement of the barbell while traveling overhead. Usually it is up to the athlete to see when they use hook grip dependent on whatever is the most comfortable to them. Hook grip is important when lifting heavy to help hang on to the bar.
Hook grip optimizes the anatomy of the hands for the application. While holding hook grip we want to make sure we stay as relaxed as possible because if you’re not relaxed you can put a ton of pressure on your thumb which can cause pain or injury.
All in all hook grip is a stronger grip and is good to use when lifting heavier. Hook grip can help you hang on to the bar for a lot longer and build grip strength.