Training with Atlas Stone curls is a terrific way to improve grip strength and arm curling power. In a seated position center your hands on the stone so each finger, thumb and palm always remain in contact with it while lifting. The elbows should remain centered to the lifter's knees, with no part of the arms ever touching the legs as the stone is raised and lowered.
Keeping the correct form during the entire movement is surprisingly difficult, this exercise dramatically improves hand and arm power. A great way to Get Strong.
The Pendulum Grip Cart