A device to strengthen a person's arm muscles through the utilization of a portable device including a handle portion and a weight component with the two components separated by a flexible rod. Such a device allows for the user to grip the handle portion and act as if they are throwing such a handle portion while the weight end moves along an arc defined through the length of the flexible rod. The resultant action is the generation of centripetal force along the defined arc with the reactive centrifugal force providing resistance to the user's arm muscles in a manner that is unique and heretofore unattainable through the utilization of a portable exercise device. The flexible rod component provides at least 10 inches (25.4 cm) of spacing between the handle portion (which may be in the form of a sphere, such as a baseball or softball, or a handle, or any other typical implement that a person may throw or swing) and the weight portion (which may be of any configuration to permit increase or decrease of the weight present thereon).