Isometric vs. Isotonic vs. Concentric vs Eccentric
- Isometric: The muscle is neither shortening nor lengthening. (Holding a position.)
- Isotonic: The muscle is either shortening and lengthening. (Moving through positions.)
- Concentric: The muscle is shortening. (Part of isotonic exercise.)
- Eccentric: The muscle is lengthening. (Part of isotonic exercise.)