A short bar with fixed or changeable weights mounted on each end with enough space in between to grip with one hand.
The term "dumbbell" comes from the practice of demonstrating strength by lifting heavy cast metal bells (like the Liberty Bell, only smaller and not cracked). A "dumb bell" was a bell made without a clapper so that it would not ring through one's show of physical prowess. Eventually, any weight meant to be hefted with one hand was referred to as a "dumbbell" and after what we now think of as being a dumbbell shape became standard, the word "bar bell" or "barbell" was coined to refer to a similar weight with a central bar long enough to be held easily with two hands.
Was this article helpful?
The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.