New technologies such as Spatial Augmented Reality (SAR) have created new opportunities for including end users in the early phases of the design process when prototypes are not always available for functional testing. This study investigates the impact of introducing SAR technology on designers and end users working together in co-design sessions. To this end, a multi-modal analysis focusing on cognitive activities and gestural behaviour was conducted. After comparing the traditional setting with the SAR setting (over 44 sessions), the session activity profiles proved to be quite similar. However, the study highlights specific correlations between gestures and cognitive activities, in both environments. Finally, contrary to expectations, free gestures continue to be made in the digitally mediated situation.