isometric exercise

from the GNU version of the Collaborative International Dictionary of English.

• noun A system of exercise to strengthen specific muscles of the body by pushing parts of the body (such as the two hands) strongly against each other, or against a fixed object, so that the muscles are strongly stressed, but are stretched only a little. It is claimed to produce strength in the muscles thus exercised. Also called isometrics.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun muscle-building exercises (or a system of musclebuilding exercises) involving muscular contractions against resistance without movement (the muscles contracts but the length of the muscle does not change)