Effects of social network incentives and financial incentives on physical activity and social capital among older women: a randomized controlled trial

Background Financial incentives have been used to increase physical activity. However, the benefit of financial incentives is lost when an intervention ends. Thus, for this study, we combined social network incentives that leverage the power of peer pressure with financial incentives. Few reports have examined the impact of physical activity on social capital. Therefore, the main goal of this study was to ascertain whether a combination of two incentives could lead to more significant changes in physical activity and social capital during and after an intervention. Methods The participants were 39 older women over 65 years of age in Kumamoto, Japan. The participants were randomly divided into a financial incentive group (FI group) and a social network incentive plus financial incentive group (SNI + FI group). Both groups underwent a three-month intervention. Measurements of physical activity and social capital were performed before and after the intervention. Additionally, the effects of the incentives on physical activity and social capital maintenance were measured 6 months postintervention. The financial incentive group received a payment ranging from US$4.40 to US$6.20 per month, depending on the number of steps taken during the intervention. For the other group, we provided a social network incentive in addition to the financial incentive. The SNI + FI group walked in groups of three people to use the power of peer pressure. Results A two-way ANOVA revealed that in terms of physical activity, there was a statistically significant interaction between group and time (p = 0.017). The FI group showed no statistically significant improvement in physical activity during the observation period. In terms of the value of social capital, there was no significant interaction between group and time. Conclusion Our results suggest that social network incentives, in combination with financial incentives, are more effective for promoting physical activity than financial incentives alone among older women and that these effects can continue after an intervention. In the meantime, further studies should be conducted on the effect of physical activity on social capital. Trial registration UMIN000038080 , registered on 09/22/2019 (Retrospectively registered).