The invention is directed to a muscle trainer and methods for exercising a weaker of two sets of opposing muscles of a person moving an implement, such as a golf club, wherein, if the two sets of opposing muscles were of appropriate strength, the two sets of opposing muscles would desirably apply forces in opposite directions to the implement to assist in maintaining an ideal movement of the implement. In various embodiments, the invention provides methods for training the opposing sets of muscles to consistently move the implement in an ideal way to accomplish a useful or recreational function. The methods include: (a) moving the muscle trainer through an actual motion; (b) determining a difference between the actual motion and an ideal motion, where the difference indicates a dominating force direction in which the muscle trainer is being urged by the stronger or dominating set of muscles; (c) applying an external force to the muscle trainer to urge the muscle trainer in the dominating force direction; and (d) using the weaker or non-dominating set of muscles to urge the muscle trainer against the external force to thereby exercise the non-dominating set of muscles.