Definition of "isotonics"

Isotonics cause more muscle hypertrophy. It is theorized that this is due to the increased capillarization which is stimulated much more by isotonics than isometrics.

1972, Clayne R. Jensen, A. Garth Fisher, Scientific basis of athletic conditioning, page 72

The development of this kind of fitness is brought about only by dynamic movement, by isotonics, usually against fairly moderate resistance, and repeated many times so that the heart and lungs have to work increasingly harder and longer as training progresses.

1984, Linda Fox, The Complete Head to Toe Exercise Book: Get Fitter, Feel Better

Hand and wrist isometrics and isotonics are performed in the sling.

2011, Robert A. Donatelli, Physical Therapy of the Shoulder, page 66