In this paper, the authors describe a mechanism for the introduction of small variations in the original learning design process defined in a particular Unit of Learning (UoL). The objective is to increase the UoL reusability by offering the designers an alternative to introduce slight variations on the original design instead of creating a new one each time they want to reuse it. No changes or extensions to the Learning Design definition are required to perform these modifications. The use of design patterns to include the adaptations offers the possibility to easily introduce new operations, such as tracing the activity progress, for instance. The structure of a Learning Design player that is able to process the desired adaptation information and to apply it at runtime will be outlined. The player will be part of an architecture for the automatic adaptation of UoLs to their actual context of execution. (Contains 11 figures and 2 tables.)