Hand strengtheners are exercise devices designed to increase the strength of your grip. Hand grip exercise equipment work on the principle of resistance training, helping to build up the muscles in your hands and forearms. Hand strengtheners can be used for a variety of purposes, from improving your grip strength for sports to helping you rehabilitate from an injury. Exercise hand grips focus on different areas of the hand so you'll want to choose one that targets the muscles you're looking to develop. Since they're portable and relatively inexpensive, they're a great choice for people who want to exercise at home.