en Health Promotion Health Promotion پژوهشي Original Article <div style="text-align: justify;"><span style="font-size:14px;"><span style="font-family:Times New Roman;"><strong>Background:</strong> Despite the health benefits of physical activity, many people still adopt sedentary lifestyles. This study aimed to investigate the effect of education based on trans-theoretical model (TTM) on physical activity of women of reproductive age in Zanjan.<br> <strong>Methods:</strong> This was a quasi-experimental study. Using convenience sampling method, the sample size of 120 women was selected and randomly allocated to study groups. The data was collected using a short version of Physical Activity Change Algorithm Questionnaire and IPAQ (International Physical Activity Questionnair) before and 3 months after intervention. In addition to training sessions, the intervention 2 group was trained to use pedometer.<br> <strong>Results:</strong> Before the intervention most of the women were in contemplation and preparation stages and 3 months after the intervention, women in intervention groups moved to action and maintenance stages (<em>P</em> < 0.001). There was significant difference in mean time of weekly walking and physical activity in three groups 3 months after the intervention (<em>P</em> < 0.001). These changes were more prominent in women who used pedometer.<br> <strong>Conclusion:</strong> The findings showed that education based on the trans-theoretical model was effective in promoting the physical activity. Using the pedometer along with education had effect on improvement of the physical activity.</span></span></div> Education, Trans-theoretical model, Physical activity, Reproductive aged women, Pedometer 115 120 http://jhehp.zums.ac.ir/browse.php?a_code=A-10-29-2&slc_lang=en&sid=1 Leila Khosronia lekho63@yahoo.com 100319475328460010296 100319475328460010296 No Department of Health Education and Health Promotion, School of Health, Zanjan University of Medical Sciences, Zanjan, Iran. Fatemeh Jafari fjafari@zums.ac.ir 100319475328460010297 100319475328460010297 Yes Department of Health Education and Health Promotion, School of Health, Zanjan University of Medical Sciences, Zanjan, Iran. Khadijeh Hajimiri hajimiri_kh@yahoo.com 100319475328460010298 100319475328460010298 No Department of Health Education and Health Promotion, School of Health, Zanjan University of Medical Sciences, Zanjan, Iran.