This project is to examine the effect of pilates exercise, which is applied by university students under the guidance of peers, on premenstrual syndrome symptoms and healthy lifestyle behaviors.

Methods: The research to be carried out within the scope of the project is randomized controlled and has an experimental research design. The population of the research consists of 385 female students studying at the Department of Midwifery at Istanbul University-Cerrahpaşa Faculty of Health Sciences. In the study, it is aimed to reach all students without making a sample calculation in order to identify the students with PMS symptoms among all students. Students who score 110 and above on the Premenstrual Syndrome Scale (PMSS) will be considered to have PMS symptoms. The sample size of the students showing PMS symptoms was determined by using the G*Power (3.1.9.2) program and considering the 0.05 margin of error and data loss, according to 95% power and medium effect size; 27 people should be included in the experimental group and 27 people in the control group. In determining the groups, the participants will be assigned to the experimental and control groups using the "Randomizer.org" program. Students included in the research will be given information about the study and will be presented with an "Informed Consent Form" and a "Volunteer Consent Form". While the experimental group will be given pilates exercises, under the guidance of a peer, for half an hour twice a week for six months, the control group will maintain their routine habits. At the beginning of the study, data will be collected with the "Personal Information Form", "Premenstrual Syndrome Scale (PMSÖ)" and "Healthy Lifestyle Behaviors Scale-II (SYBDS-II)". In the third and sixth months of the study, the hypotheses will be tested by applying PMSS and HLBS-II. The data obtained in the research will be entered into the database in the IBM SPSS 25.0 (Statistical Package for the Social Sciences) program and all necessary statistical analyzes will be performed in the same program.

Inclusion Criteria:

• Being an undergraduate student studying in the midwifery department of Istanbul University-Cerrahpaşa Faculty of Health Sciences,
• Having a score of 110 and above in PMSS,
• Having an internet connection,
• The Zoom program is installed and ready to use on its electronic device (phone or computer),
• Having the environment to do Pilates.

Exclusion Criteria:

• Being under the age of 18,
• Changes in menstruation characteristics after the diagnosis of PMS,
• Having a chronic or physical illness that prevents Pilates exercise.