Ivy Tech APHY 101 – Muscle System Practice Test

Isotonic contractions are the ones where the muscle changes its length while the tension stays essentially constant. When you move a constant-load, the muscle shortens (concentric) or lengthens (eccentric) while producing about the same force throughout the motion. Isometric contractions, in contrast, generate increasing tension without any change in length. Treppe describes a staircase increase in force with repeated stimuli at the same length, and wave summation is about increased force from higher stimulus frequency with incomplete relaxation. So the situation of a changing length with constant tension fits isotonic contractions.