GLOSSARY

An isotonic contraction is traditionally one in which the muscle shortens or lengthens against a constant external load through the range of motion, comprising concentric and eccentric phases.
The word comes from the Greek iso, meaning “equal”, and tonos, meaning “tension”.

Important Scientific Note

The name “isotonic” means “constant tension”, but in reality muscle tension is not constant during the movement, because as the joint angle changes, the moment arms of the load and the muscle and the length–tension relationship all change. For this reason many experts prefer the more accurate terms isoinertial or dynamic constant external resistance (DCER)