Prestwich, A., Conner, M. T., Lawton, R. J., Ward, J. K., Ayres, K., & McEachan, R. R. (2012). Randomized controlled trial of collaborative implementation intentions targeting working adults' physical activity. Health Psychology, 31(4), 486.
Adults were asked to form collaborative implementation-intentions to exercise more. They read, "Past research suggests that despite intending to undertake regular physical activity, many people fail to do so. To give yourself the best chances of succeeding, it seems that it can be helpful to make a very specific plan with a partner (e.g., husband, wife, girlfriend, boyfriend, housemate, etc.) about how together you will go about increasing the amount of regular physical activity you do" and then completed "If…then…we" statements. As compared to participants in a control condition, in a personal implementation intentions condition, and in a partner but no implementation intentions condition, those in the collaborative implementation-intentions condition engaged more frequently in physical activity one and six months later and reported losing more weight six months later.