Abstract: An exercising machine having improved control permitting either an assist or a resistance of the exercise being performed comprises a first member exercisingly movable by a part of the body against the resistance of a weight or spring and a second member operable by another part of the body with the second member advantageously comprising a pivotable lever, with a linkage selectively engageable between the second member and the weight or spring in two modes in which force applied to the second member in the same direction respectively assists and resists movement of the first member.