Actually, this is also the first time that I have heard of it, and based on the name; it has something to do with strengthening the grip. Upon my research, here is what I found; strengthening the grip gains its popularity because of the Strongman Challenge, wherein you need to reap a phone or bend bolts of steel. Of course, you do understand that those two activities are impossible because our grip is not made to do that. Well, you can do anything you want if you prepare for it or in this case train for it.
If you want to strengthen the grip then you need to know the four muscles groups involved. 1) The hand closing muscles, 2) The hand opening muscles, 3) The risk flexing muscles, and the 4) wrist extending muscles. Most hand exercise program doesn’t exercise all four muscles.
Most people that try to strengthen their grip only do the hand closing muscles. These can be found in the finger and thumb flexor muscles and adductor muscles. However, the question remains if you are able to train the muscles in proper plain. The most popular way to strengthen the fingers is to use some sort of spring-loaded or coiled resistance devices. Such training method can harm your hand in the long-term as the hand muscles are trained in unnatural position. We need a device that would help train the hand in three dimensional planes, so that the movement would be natural.
Wrist flexion is another way to exercise the grip. This is usually done with a dumbbell or a weighted object tied to a rope and dowel. Most people incorporate the third common grip exercise with wrist extension. Wrist extension is trained with a dumbbell, also with a dowel tied to a rope and a wooden dowel. This is a great way to exercise both the wrist flexor muscles and the wrist extensor muscles.
The “hand opening muscles” are the most vital in strengthening the grip. The muscles that are trained here are the finger and thumb extensor. Both of these hand muscles are used to open the hand (when necessary), and the second is to contract in a stabilizing and complementary mode to support the action of the finger flexor muscles. You can use a rubber band to strengthen such muscles. Here is what you need to do:
Wrap a rubber band around your hand at the base of your finger joints.
Gently move the thumb from your other fingers as far as possible.