Emerging technologies such as exoskeletons and electrical muscle stimulation can initiate movement within the human body, blurring the boundary between user and machine. While prior research has explored how such systems augment bodily action, most focus on movement execution rather than decision-making. In this work, we investigate what happens when a bodily-integrated system acts with its own logic and initiates bodily movement alongside users. We present three game scenarios where an exoskeleton controls one arm while the user controls the other, designed to evoke different relational framings: proxy, collaboration, and opposition. Through a qualitative study (N = 16), we examine how users interpret such interactions, and how shared bodily control shapes bodily experience and human-machine relationship. We further contribute a set of implications for designing bodily technologies that decide and move together with users, opening up design possibilities for systems that share bodily control, not merely actuate on users' behalf.
ACM CHI Conference on Human Factors in Computing Systems