Which type of muscle contraction is characterized by a muscle shortening while developing tension?

The correct choice is isotonic contraction, which refers to a type of muscle contraction where the muscle shortens and develops tension simultaneously. In isotonic contractions, the muscle fibers generate enough force to overcome the resistance, typically resulting in movement at a joint. This process allows for actions like lifting weights or performing physical activities where the tension in the muscle leads to a decrease in muscle length.

In contrast, isometric contractions involve the muscle generating tension without changing its length, meaning there is no movement despite the muscle working. Isovolume and isovelocity are terms that pertain to conditions under specific experimental setups, often relating to consistent volume or velocity during contractions, but they are not standard types of voluntary muscle contractions like isotonic or isometric. Thus, the nature of isotonic contractions is distinguished by both the shortening of the muscle and the development of tension necessary for movement.