A training device was any device whose function was to control or re-condition an individual's movements or actions.

In 2268, James T. Kirk questioned Montgomery Scott's assessment of the Eymorg women's intelligence or, rather, lack of it, as they had apparently invented the training devices the landing party members now wore. (TOS: "Spock's Brain")

Motor assist bands were another type of training device. In 2368, Doctor Toby Russell referred to them thusly when explaining Worf's rehabilitation to him. (TNG: "Ethics")