Which initiation type is characterized by the absence of any preliminary lengthening?

The initiation type characterized by the absence of any preliminary lengthening is indeed non-countermovement. In this type of movement, the athlete initiates the action without first going through a preparatory or eccentric phase that lengthens the muscle. This contrasts with counter-movement types, where the body first lowers to build potential energy before jumping or exerting force.

In non-countermovement, the takeoff occurs directly from a static position, allowing for a more rapid push-off, as there is no delay caused by lowering the center of mass. This type can be beneficial in certain performance contexts where immediate force generation is key, such as in specific sprinting or jumping actions.

Other options involve some form of preparatory movement or lengthening phase, which makes them different from non-countermovement. Understanding the dynamics of how each type affects force production can enhance training strategies to optimize performance outcomes.