A randomised controlled trial (RCT) to investigate the effectiveness of a public health campaign to increase people's confidence in becoming more active despite low back pain in comparison with no intervention.

The video interventions are between 2 and 3 minutes long and have been designed specifically for this study. Both follow the same narrative that scientists would like to reassure the public that low back pain is common, and that evidence suggests it is safe to move despite back pain. The featured scientists report that they are unsure of how to convey these messages to the public, which leads to designers at the advertising agency brainstorming how to help deliver the key message that it is safe to move. The advertising agency personnel suggest a dance. The video cuts back to the scientists who are reluctant to endorse one specific movement, such as a dance and conclude that it does not matter what you do as long as you move. The video ends with the superimposed text, "It's safe to move", "Your backbone has backbone". The second video is the same as the first, except that when the advertising agency suggests the dance, the scientists try it out and to add humour, there are some video clips of the scientists dancing. Participants will access the intervention videos once only. Participants will be provided with a link and expected to watch the video where they would usually access social media, for example at home, or on public transport. The study will be advertised through social media channels over a period of 6 months or until we achieve the required sample size. Participants will watch one of the intervention videos only. This is a social media-based intervention. We will assess and monitor adherence to the intervention, by analysing the information provided by the survey platform, including % of survey completed and the time spent on survey