  Extended reality (XR) technologies are highly suited in assisting individuals
in learning motor skills and movements -- referred to as motion guidance. In
motion guidance, the "feedforward" provides instructional cues of the motions
that are to be performed, whereas the "feedback" provides cues which help
correct mistakes and minimize errors. Designing synergistic feedforward and
feedback is vital to providing an effective learning experience, but this
interplay between the two has not yet been adequately explored. Based on a
survey of the literature, we propose design space for both motion feedforward
and corrective feedback in XR, and describe the interaction effects between
them. We identify common design approaches of XR-based motion guidance found in
our literature corpus, and discuss them through the lens of our design
dimensions. We then discuss additional contextual factors and considerations
that influence this design, together with future research opportunities for
motion guidance in XR.
