The present study examined the effectiveness of a web-based intervention and educational software designed to promote students' physical activity. In this study, physical activity increased significantly after the intervention in the web and software groups compared to the control group. Before the intervention in groups of software 2.9% and web 3% had moderate physical activity and none had intense physical activity. After the intervention in the software group, 46.4% had moderate activity and 47.8% had intense physical activity and in the web group 48.5% had moderate activity and 36.4% had intense activity. These results confirm the effectiveness of web and software-based interventions on promoting students’ physical activity, consistent with the study results of Foster , Bell , Vandelanotte , Hargreaves , and Zolfaqari . In Carroll's study, although an increase was observed in physical activity after the intervention, this difference was not statistically significant .
Internet behavior change interventions have the potential to reach a large audience at low cost.
The short-term effectiveness of web-based physical activity interventions in previous studies has made participants' retention and participation a challenge . Fjeldsoe's study on maintaining a change in physical activity performance suggests that increasing the duration of the intervention or creating long-term follow-up messages in the program may be useful in achieving this goal . In this study, the researcher provided the opportunity to always be with the participants and answer their questions by texting and emailing during the 6-month intervention and follow-up. In addition, motivating students by showing motivational videos, enhancing self-efficacy, teaching strategies to overcome obstacles, and creating commitment are other reasons. Maintaining behaviors by a six-month follow-up for the majority of students confirms the success of this program. In Maher study , a significant increase was found in physical activity after the intervention, but after 3 months, it was not significant, which is inconsistent with our study and can be attributed to the 6-month follow-up of the research team in the present study.
The study also showed that those in the software group performed better on physical activity than the web group. The reason can be easier and faster access to the training program in this group than the group that needed the Internet to get the program. No study was found that compared these 2 methods of intervention. Therefore, no comprehensive and reliable comparison is possible between our study results and previous studies in this regard.
Finding information that support the behavior change and knowledge of the undesired outcomes of behavior has always been one of the main processes of change  that cannot be ignored. In this study, first the mean score of knowledge in all 3 intervention and control groups was high, which seems reasonable given that our target group composed of medical students. However, after the intervention in all 3 groups, the mean score of knowledge increased, which was higher in the intervention groups and statistically significant, which can be attributed to the intervention effect. In the control group, also students' curiosity to know the answers to questions they did not know and seek information in this regard could be the reason of this increase.
Studies show that improving individual attitudes increases individuals' participation in the behavior . This study significantly increased students' attitude score toward physical activity after training in the intervention group by creating a positive interest and attitude in students towards sport activities. The perceived benefits and obstacles of the behavior, especially at pre-contemplation and contemplation stages, are important for making a change. Therefore, in this program, while focusing on the benefits of regular physical activity, practical solutions were presented to overcome the existing barriers. After the intervention, perceived benefits in the intervention groups significantly increased and perceived obstacles reduced. This result suggests that the subjects have evaluated the benefits and obstacles of the behavior change, considered the change as both feasible and valuable and made it . This result is consistent with the results of similar studies [41–43] .
Usually as a result of the action, the obstacles become more pronounced, and less as the behavior continues, and with increasing self-efficacy the behavior is also more likely to be retained. The perceived self-efficacy in relation to physical activity was another variable that was investigated in this study. The exercise self-efficacy, derived from Bandura's social cognitive theory, expresses one's beliefs or judgments of one's ability to perform regular physical activity . In this study, after familiarizing students with the concept of self-efficacy, various strategies were used to reinforce it, such as breaking down complex behaviors into small, practical and executable stages, modeling and rewarding themselves. The results showed that self-efficacy in the experimental groups increased after the intervention. However, self-efficacy in the control group showed no significant change, which is consistent with the study results of Lari and Mehdizadeh  .
The low mean score of action planning before the intervention in all 3 groups in this study indicated that students were not aware of the importance of planning for performing the behavior. In the intervention groups, with emphasis on planning, prioritizing tasks, and writing realistic and achievable goals, the students were taught how to write a good, flexible schedule for regular physical activity. The study results after the intervention showed a significant increase in the mean score of planning in the 2 intervention groups compared to the control group, which was still high 2 and 6 months later.
Studies have shown that the possibility of performing behaviors in which one is admired or socially reinforced is increased . Regarding the low scores of individual factors in all 3 study groups, several strategies were trained to identify and attract these supports. The results showed that in the intervention groups, the mean score of individual factors after training was significantly higher than the control group, which is consistent with Lari study .
According to the results of the present study, the mean commitment score was low in all 3 groups before the intervention. But immediately after the intervention, the mean score of this construct in the experimental groups was significantly higher than the control group, indicating the effect of the educational program. In this program, emphasizing the role of commitment in the behavior, the students were taught ways to have commitment and were asked to sign and adhere to a commitment made in this regard. A strong commitment to action may save a person from competing demands. The competitive priorities and demands both directly affect the possibility of health behavior and reduce the effect of commitment to action . Regarding the important role of this construct in the behavior, students were given training for identifying inactive behaviors and replacing them with regular physical activity. The higher scores of this construct indicated a negative impact on physical activity at the beginning of the study in all 3 groups. But after the intervention, a significant reduction was observed in the intervention groups. According to Bandura, positive or negative feelings are coded before, during, or after the behavior in the mind and when a behavior is initiated in the future it will be reminded, and these cognitions and emotions shape the behavior . In this study, higher scores on the behavior-related emotion constructs indicated a good sense of behavior. Before the intervention, it was low in all 3 groups. The program provided guidance on how to change the way students look and feel about physical activity and help students feel positive about regular physical activity. The results showed a significant increase in the mean score of this construct in the intervention groups after the intervention.