Canada's 24-Hour Movement Guidelines for Adults ("Guidelines") integrate recommendations for multiple movement behaviours. Most Canadian adults do not meet behaviour recommendations for physical activity, sedentary behaviour and sleep. Historically, movement behaviours were presented in isolation from one another, using complex and overwhelming thresholds outlining duration and intensity for optimal health. Compared to threshold messages, generic messages encouraging small, but meaningful, behaviour change may improve adults' confidence to engage in optimal movement patterns. This study aimed to experimentally test if a novel, generic style messaging approach fostered stronger perceptions of self-efficacy to meet the Guideline recommendations, compared to a traditional, threshold approach. Canadian adults (N=247) were randomly assigned to an intervention or control group. Guideline promotional materials with generic messaging and threshold messaging were provided to the intervention and control groups, respectively. Both groups completed online surveys at two-time points examining self-efficacy and indicators of message processing. Hierarchal linear regressions predicting adults' confidence to meet the Guidelines revealed an activity status by experimental condition interaction. Post hoc analyses indicated low active adults exposed to generic messages had greater confidence to meet the Guidelines compared to low active adults exposed to threshold messages. Additionally, message processing was greater among adults exposed to the generic materials than the threshold materials. The findings emphasize that generic messages may be advantageous for promoting adults' confidence to meet movement guidelines. This work has implications for researchers and health promoters aiming to develop appropriate messages for health behaviour engagement among Canadian adults.