Isokinetics is a fancy word describing a form of muscular contraction where movement is at a constant constant speed, no matter how much force is applied. Coaches always loved isokinetic machines because they were cheap and manufacturers loved isokinetic machines because they didn’t require a weight stack making them both cheaper to produce and cheaper to ship. Do isokinetics really work for building muscle? Who cares? –the machines are cheap and they give athletes something to do during gym class. This advertisement is by the Mini Gym Co. from 1974.