The aim of this randomized controlled trial is to observe the effectiveness of cryotherapy application in nulliparous women with primary dysmenorrhea regarding pain intensity, sleep quality and quality of life. It is also intended to analyse whether the levels of physical activity and the socioeconomic status of the participants are determining factors.

For the recruitment of participants (whose minimum n will be calculated using the G*Power computer software) an online dissemination campaign will be carried out through social networks, physiotherapists specialised in pelvic floor dysfunctions and gynaecologists will be contacted to inquire about the availability of patients who can participate, and students from both the University of Malaga and the University of Valencia will be contacted through official communication channels.

Nulliparous women with primary dysmenorrhea who meet the following inclusion criteria will be recruited: (1) Menstrually active women between the ages of 18 (to avoid guardian authorizations) and 45 (age of onset of menopause according to the National Institute of Aging ), (2) Menstrual cycles ranging from 24 to 38 days according to OASH , (3) Menstrual periods of 3 to 7 days, and (4) Pain lasting 1 to 3 days. Women with a history of underlying diseases causing secondary dysmenorrhea, women with systemic and/or psychiatric illnesses, and women with a history of use of hormonal medications, oral contraceptive pills, or intrauterine devices will be excluded.

The intervention will consist of applying a cold pack to the hypogastric region, with the participant lying supine, twice daily for the first three days of menstruation. Participants will be required to keep an application calendar where they will note when they have applied the cold pack, and will record the variables of interest for this study before and after its application. Three menstrual cycles will be monitored, where researchers responsible for the research team will periodically contact the participants to ensure adherence to the treatment. Participants randomized to the control group will not undergo intervention during this period.

For the dependent variables; pain intensity assessed by the Visual Analogue Scale, sleep quality assessed by the Pittsburgh Sleep Quality Index and quality of life assessed by the World Health Organization Quality of Life Brief Version questionnaire, a statistical analysis will be performed using the repeated measures ANOVA test to determine the evolution of these variables during the three menstrual cycles. A posteriori, a correlation analysis will be performed between the results of this test and the physical activity levels of the participants, assessed using the International Physical Activity Questionnaire-Short Form , in addition to the socioeconomic status, assessed using the Kuppuswamy Socioeconomic Status Scale .

Inclusion Criteria:

• Menstrually active women
• Menstrual cycles that vary between 24 and 38 days according to the OASH
• menstrual periods between 3 and 7 days, and
• Pain lasting from 1 to 3 days

Exclusion Criteria:

• Patients suffering diseases that generate secondary dysmenorrhea, with systemic or psychiatric diseases, and patients with a history of use of hormonal medication, birth control pill, or intrauterine devices