Abstract
BACKGROUND: Mobile technology offers great potential for physical activity promotion, especially by facilitating online communication, however, the impact of group communication norms on intervention effectiveness remains unclear. This study aimed to evaluate the effect on daily steps of a team-based social norms-related intervention using a mobile application. METHODS: The 13-week quasi-experimental study was conducted in Shanghai, China, from September to November 2019, involving 2,985 employees from 32 worksites. For the intervention group (n = 2,049), participants set a goal of 10,000 steps per day. The teams and individual members would receive points for meeting the daily goal, contributing to team-based rankings and financial rewards for the teams and their members. In addition, the intervention teams created dedicated WeChat groups to facilitate communication, which were also used to collect group chat messages. The communication type in these groups was classified into four types: (1) nudging - encouraging team members to be more active, (2) sharing - exchanging the completion of daily step goals, (3) feedback - providing responses or suggestions to team members, and (4) other -diverse topics that could not be classified otherwise. The control group only tracked their steps online. RESULTS: The weekly average steps of the intervention group increased by 2,523 steps, while the control group increased by 470 steps. In the first 3 weeks of follow-up, the frequency of nudging of 7-18 times/week had a positive cumulative effect on the step counts. Sharing more than 3 times/week had a positive cumulative effect. Over 6 and 13 weeks of follow-up, nudging 19 times/week or more had a positive cumulative effect while sharing and feedback at any frequency negatively affected average weekly steps. CONCLUSIONS: Communication types within a team affected team-based step counts in a financial incentive intervention. The team-level social norms related to communications might have different cumulative effects on team-level physical activity. 'nudging' messages had a significant association with the change in individual-level step counts in the medium or long term. TRIAL REGISTRATION: Pilot Project of the application of walking incentive technology in occupational groups, 2019, ChiCTR1900023813. Registered 13 June 2019, https://www.chictr.org.cn/showproj.html?proj=39858 .