Abstract: An exerciser is disclosed, of the type providing automatically controlled variations of effort levels, wherein "random" variations of effort level are included which are not predictable by the operator. The effort levels [steps] are provided in a sequence of four: the second [step] level is random; the fourth [step] level is different from the second [step value] level by half of the range; and the first and third [steps] levels are averages of the immediately preceding and immediately following [steps] levels.